JP2003324252A - Semiconductor distribution bragg reflector, surface- emitting semiconductor laser element, surface-emitting laser array, surface-emitting laser module, optical interconnection system, and optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor Bragg reflector capable of reducing resistance and light absorption loss without reducing a reflection factor. <P>SOLUTION: A p-type semiconductor distribution Bragg reflector I and a p-type semiconductor distribution Bragg reflector II which are successively laminated in the lamination direction are different in thicknesses at intermediate layers (linear composition inclination layer). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a semiconductor distributed Bragg reflector, a surface emitting semiconductor laser device, a surface emitting laser array, a surface emitting laser module, an optical interconnection system and an optical communication system.

[0002]

2. Description of the Related Art Conventionally, a distributed Bragg reflector (DBR) having a reflection band in the 0.85 μm band and a 0.98 μm band, and a surface emission of the same wavelength band using such a distributed Bragg reflector as a resonator mirror. Semiconductor laser devices are known. The distributed Bragg reflector is formed by alternately stacking materials having different refractive indexes to a thickness of ¼ of the wavelength of light in the medium, and utilizes multiple reflection of light waves at the interface.
It is possible to obtain a reflectance as high as the above.

Further, the surface emitting semiconductor laser device is suitable as a light source for optical interconnection and image processing systems because it has a low oscillation threshold current, can operate at high speed, and can be easily two-dimensionally integrated. Attention has been paid. The surface-emitting semiconductor laser device requires a resonator mirror having a high reflectance of 99% or more because the region where the optical gain is generated is only a part of the resonator region and the resonator length is short. A distributed Bragg reflector is suitable for this resonator mirror.

The material of the distributed Bragg reflector includes, for example, a semiconductor material or a dielectric material. In particular, a semiconductor distributed Bragg reflector made of a semiconductor material can be energized and is suitable for application to a surface emitting semiconductor laser device. Are suitable.

Conventionally, as such surface-emitting semiconductor laser devices, 0.85 μm band and 0.98 μm band devices made of AlGaAs material using GaAs as a substrate have been known. In this material system, AlGaAs material is used. A semiconductor distributed Bragg reflector is used as the cavity mirror.

A semiconductor distributed Bragg reflector made of an AlGaAs material is composed of two types of AlGaAs layers having different Al compositions, a semiconductor layer having a large Al composition (for example, an AlAs layer) is used as a low refractive index layer, and As the high refractive index layer, a semiconductor layer having a small Al composition (for example, GaA
s layer) is used. In a typical example of a surface emitting semiconductor laser device, semiconductor distributed Bragg reflectors, which are respectively p-type and n-type doped, sandwiching an active layer, are provided.
Light waves are confined and carriers are injected into the active region.

Further, in the surface emitting semiconductor laser device, for the purpose of reducing the threshold current density, an Al (Ga) As selective oxidation layer is oxidized on a part of the p-type semiconductor distributed Bragg reflector near the active layer. A structure is known in which a current constriction layer (Al ₂ O ₃ ) obtained by the above is provided. The current confinement layer made of Al ₂ O ₃ is a good insulator, and holes, which are carriers, are confined by the current confinement layer and injected into the limited region of the active layer. Can be increased to the threshold carrier density required for oscillation,
As a result, a low threshold current of sub milliamperes can be obtained. Further, since the refractive index of the selective oxidation layer is lower than that of the semiconductor layer, it acts as a confinement layer for the transverse mode, and in the 0.98 μm band element, the confinement diameter is reduced to about 4 μm or less, One fundamental transverse mode oscillation can be obtained.

However, as described above, the stenosis diameter is 4
In the element narrowed down to about μm or less, there is a problem that the area of the current passage in the narrowed region is reduced and the electric resistance is greatly increased. In the element having the narrowed diameter down to the above size, the current state is that the stenosis resistance caused by the stenosis occupies more than half of the element resistance. The increase in resistance of the element causes various problems such as increase in operating voltage, output saturation due to heat generation, and decrease in modulation speed.In order to reduce resistance due to constriction, the resistance in the constricted region and the resistance around it are reduced. It is necessary to reduce it.

The cause of the high resistance due to the narrowing is that the resistance of the p-type semiconductor distributed Bragg reflector is essentially high. Different p-type semiconductor materials have different band gaps.
The effect of the potential barrier generated at the hetero interface of the seed semiconductor layer is large, and the resistance is extremely high as compared with the n-type semiconductor distributed Bragg reflector made of the n-type semiconductor material.

Conventionally, in order to reduce the electric resistance of a p-type semiconductor distributed Bragg reflector, for example, in a surface emitting semiconductor laser device in the 0.98 μm band or the like, a reference "Photonics" has been used.
Technology Letters Vol.2, No.4, 1990, pp234-236,
Photonics Technology Letters Vol.4, No.12, 1992,
As shown in "pp1325-1327" and the like, between the two kinds of layers having different Al compositions, which constitute the distributed Bragg reflector,
It is known to provide a hetero barrier buffer layer such as a compositionally graded layer having an Al composition intermediate between these.

As described above, in the surface emitting semiconductor laser device, the reduction of the resistance of the device is an important issue, and particularly the reduction of the resistance of the p semiconductor distributed Bragg reflector is actively studied.
Development is underway. To reduce the resistance, it is very effective to provide the above-mentioned hetero barrier buffer layer, and further, the semiconductor layers constituting the semiconductor distributed Bragg reflector, particularly the hetero barrier buffer layer and the doping concentration in the periphery thereof, can be controlled. It is very effective to raise it.

However, in a heavily doped p-type semiconductor, electrical characteristics such as device resistance can be improved, but free carrier absorption of holes and absorption between valence bands become remarkable, and optical characteristics are increased. There is a problem that the physical characteristics deteriorate. In particular, in a surface emitting semiconductor laser device, in order to improve the power conversion efficiency of the device, it is important to reduce the absorption of the oscillation light by the p-type semiconductor distributed Bragg reflector. It is necessary to solve the contradictory issue of reducing absorption loss at the same time.

As a means for solving this problem, Japanese Patent Laid-Open No.
01-332812, in a surface emitting semiconductor laser device using a semiconductor distributed Bragg reflector, the doping concentration of the semiconductor distributed Bragg reflector corresponding to the active layer side is relatively low with respect to the region distant from the active layer, Further, it is shown that the semiconductor distributed Bragg reflector is configured to reduce the difference in the band gap between the two types of semiconductor layers having different refractive indexes.

In this prior art, as a method of improving the deterioration of the light output due to the influence of the light absorption by the semiconductor distributed Bragg reflector, the doping concentration of the semiconductor distributed Bragg reflector located in the vicinity of the active layer is adjusted to the doping of other regions. It is configured to be lower than the concentration. Further, in order to prevent an increase in the electrical resistance of the semiconductor distributed Bragg reflector due to the reduction of the doping concentration, the difference in the forbidden band widths of the semiconductor layers forming the semiconductor distributed Bragg reflector in the low-concentration doped region is set to , And the height of the potential barrier generated at the hetero interface is reduced by making it smaller than the difference in the forbidden band in other regions. In the surface emitting laser device having such a structure, the saturation point of light output can be high and the device resistance can be low.

[0015]

As described above, Japanese Patent Laid-Open No.
In 01-332812, for the purpose of reducing light absorption, the doping concentration in the region near the active layer is reduced,
Further, in order to prevent an increase in electrical resistance due to this, the difference in the forbidden band width between the two types of semiconductor layers forming the semiconductor distributed Bragg reflector is reduced.

However, although the effect of lowering the resistance to some extent can be obtained by reducing the difference in the forbidden band widths of the semiconductor layers forming the hetero interface in this way, in reality, the heterogeneity is reduced by reducing the doping concentration. Increasing the influence of the interface is unavoidable, and there was a limit to sufficiently reducing the electrical resistance.

In the device disclosed in Japanese Unexamined Patent Publication No. 2001-332812, by reducing the difference in band gap, the reflectance of the semiconductor distributed Bragg reflector is remarkably lowered, and the semiconductor distributed Bragg reflector inside There is a problem that the amount of light seeping out to the lens becomes large. Further, since the reflectance of the region where the difference between the band gaps is reduced is lowered, there is also a problem that the number of stacked semiconductor distributed Bragg reflectors must be increased in order to compensate for this reduction.

According to the present invention, the reflectance is not lowered.
An object of the present invention is to provide a semiconductor distributed Bragg reflector having a low resistance and a small light absorption loss, a surface emitting semiconductor laser device, a surface emitting laser array, a surface emitting laser module, an optical interconnection system and an optical communication system.

[0019]

In order to achieve the above-mentioned object, the invention according to claim 1 is such that a refractive index between two kinds of semiconductor layers having different refractive indexes is set between the two kinds of semiconductor layers. In the semiconductor distributed Bragg reflector having the intermediate layer, the thickness of the intermediate layer in some regions of the semiconductor distributed Bragg reflector is different from the thickness of the intermediate layer in other regions.

According to a second aspect of the present invention, in the semiconductor distributed Bragg reflector according to the first aspect, the difference in the forbidden band width of the two types of semiconductor layers in the region where the thickness of the intermediate layer is large is the intermediate band width. It is characterized in that it is smaller than the difference in band gap between the two types of semiconductor layers in the region where the layer thickness is thin.

According to a third aspect of the present invention, in the semiconductor distributed Bragg reflector according to the first aspect or the second aspect, the semiconductor distributed Bragg reflector is responsive to the electric field intensity of light in the semiconductor distributed Bragg reflector. It is characterized in that the thickness and the doping concentration of the intermediate layer in the chamber are different.

According to a fourth aspect of the present invention, in the semiconductor distributed Bragg reflector according to the third aspect, the thickness of the intermediate layer is large in a region where the electric field intensity of light in the semiconductor distributed Bragg reflector is large. While the impurity doping concentration is low, the intermediate layer is thin and the impurity doping concentration is high in the region where the electric field intensity of light is low.

According to the invention of claim 5, in the semiconductor distributed Bragg reflector according to any one of claims 1 to 4, the design reflection wavelength of the semiconductor distributed Bragg reflector is more than 1.1 μm. It is characterized by long waves.

The invention according to claim 6 is characterized in that the semiconductor distributed Bragg reflector according to any one of claims 1 to 5 is used.

According to a seventh aspect of the invention, in the surface emitting semiconductor laser device according to the sixth aspect, the group III material of the active layer is Ga or In, or all of them.
It is characterized in that the group V material of the active layer is any or all of As, N and Sb.

The invention according to claim 8 is characterized in that it is constituted by the surface emitting semiconductor laser device according to claim 6 or 7.

The invention according to claim 9 is the surface-emitting semiconductor laser device according to claim 6 or 7, or
The surface emitting laser array according to claim 8 is used.

Further, the invention according to claim 10 is the same as claim 6
An optical interconnection system configured by using the surface emitting semiconductor laser device according to claim 7, the surface emitting laser array according to claim 8, or the surface emitting laser module according to claim 9.

Further, the invention according to claim 11 is the same as claim 6.
An optical communication system configured by using the surface emitting semiconductor laser device according to claim 7, the surface emitting laser array according to claim 8, or the surface emitting laser module according to claim 9.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

First Embodiment In the first embodiment of the present invention, an intermediate layer (semiconductor layer) having a refractive index between the two types of semiconductor layers is provided between the two types of semiconductor layers having different refractive indices. In the semiconductor distributed Bragg reflector having the structure, the thickness of the intermediate layer (semiconductor layer) in some regions in the semiconductor distributed Bragg reflector is different from the thickness of the intermediate layer (semiconductor layer) in other regions. It has a feature.

FIG. 1 is a view showing a concrete example of a semiconductor distributed Bragg reflector according to the first embodiment of the present invention. The semiconductor distributed Bragg reflector shown in FIG. 1 is a p-type semiconductor distributed Bragg reflector having a design reflection wavelength of 0.98 μm, and is manufactured on a GaAs substrate by using the MOCVD method as a crystal growth method.

To fabricate the p-type semiconductor distributed Bragg reflector shown in FIG. 1, trimethylaluminum (TMA) and trimethylgallium (TMG) are used as group III raw materials, and arsine (AsH ₃ ) gas is used as group V raw material. It is used. CBr ₄ is used as the p-type dopant.

The semiconductor distributed Bragg reflector of FIG. 1 is constructed by sequentially stacking a p-type semiconductor distributed Bragg reflector I and a p-type semiconductor distributed Bragg reflector II, and constitutes a semiconductor distributed Bragg reflector. As shown in FIG. 2, between two semiconductor layers having different refractive indexes, an intermediate layer (semiconductor layer) having a refractive index between the two semiconductor layers is formed from one composition to another composition. A linear composition gradient layer having a linear composition change is provided. Here, FIG. 2 is a diagram showing band energy around the linear composition gradient layer. In the MOVCD method, the composition of AlGaAs can be controlled by changing the supply amount of the raw material, so that the compositionally graded layer can be easily grown.

In the semiconductor distributed Bragg reflector of the first embodiment, the p-type semiconductor distributed Bragg reflector I and the p-type semiconductor distributed Bragg reflector II, which are sequentially stacked in the stacking direction, form an intermediate layer. The thickness of the (linear composition gradient layer) is different.

FIG. 3 shows the structure of the p-type semiconductor distributed Bragg reflector I of FIG. 1, and FIG. 4 shows the structure of the p-type semiconductor distributed Bragg reflector II of FIG.

FIG. 3 shows one cycle of stacking in the p-type semiconductor distributed black reflector I of FIG.
In the Bragg reflector I, p-AlAs is used as the low refractive index layer and p-Ga is used as the high refractive index layer.
As is used. Further, an intermediate layer (p-AlGaA) having a thickness of 60 nm is provided between each of these semiconductor layers.
s linear composition gradient layer) is provided, the configuration shown in FIG. 3 is defined as one period, and the semiconductor distributed Bragg reflector of FIG.
The cycles are stacked.

FIG. 4 shows one cycle of stacking in the p-type semiconductor distributed black reflector II of FIG. 1. Referring to FIG. 4, in the Bragg reflector II, p is used as the low refractive index layer. -AlAs is used, and p-GaAs is used as the high refractive index layer. An intermediate layer (p-A) having a thickness of 30 nm is provided between each of these semiconductor layers.
1GaAs linear composition gradient layer) is provided, and the structure shown in FIG. 4 is set as one cycle, and 20 cycles are stacked in the semiconductor distributed Bragg reflector of FIG.

That is, in the first embodiment, a semiconductor distribution Bragg having an intermediate layer (composition gradient layer) having a refractive index between the two types of semiconductor layers is provided between the two types of semiconductor layers having different refractive indices. In the reflector, the thickness of the intermediate layer (composition gradient layer) in part of the region I (Bragg reflector I) in the semiconductor distributed Bragg reflector is set to the thickness of the other region II (Bragg reflector I).
It is thicker than the intermediate layer (composition gradient layer) in II).

Here, in the Bragg reflectors I and II,
The thickness of each layer forming the Bragg reflector is adjusted so as to satisfy the multiple reflection phase condition of the distributed Bragg reflector including the intermediate layer (composition gradient layer). In particular,
The thickness of the p-AlAs layer in the Bragg reflector I is 1
2.3 nm and the thickness of the p-GaAs layer is 20.3 n
m. In addition, p-AlA in the Bragg reflector II
The s layer has a thickness of 51.6 nm, and the p-GaAs layer has a thickness of 40.9 nm.

The p-type semiconductor distributed Bragg reflector of FIG. 1 is designed so that light is incident from the Bragg reflector I side, and the doping concentration of impurities in the region I (Bragg reflector I) is Area II (Bragg reflector
Doping is performed to, for example, about 5 × 10 ¹⁷ cm ⁻³ so that the doping concentration of the impurities in II) is lower.

As described above, by reducing the impurity doping concentration in the region I (Bragg reflector I) where the electric field intensity of light is relatively large, which is the incident side of light, the free carrier can be obtained as in the prior art. It is possible to reduce light absorption loss due to absorption and absorption between valence bands.

Further, in the semiconductor distributed Bragg reflector of FIG. 1, the thickness of the composition gradient layer in the region I (Bragg reflector I) where the doping concentration is relatively low is 60 nm.
And, it is made thicker than the region II (Bragg reflector II).

When the impurity concentration is low, the electric resistance increases due to the influence of the potential barrier at the hetero interface, but in the semiconductor distributed Bragg reflector of FIG. 1, the region I (where the doping concentration is relatively low) is used. By making the compositionally graded layer in the Bragg reflector I) as thick as 60 nm, the potential barrier can be sufficiently smoothed. As a result, it is possible to prevent the resistance of the device from increasing due to the influence of the hetero interface due to the low impurity doping concentration. Also,
By making the doping concentration low, a semiconductor distributed Bragg reflector having excellent optical and electrical characteristics with low light absorption loss can be obtained.

In the first embodiment, the semiconductor distributed Bragg reflector can be manufactured by crystal growth on the GaAs substrate by the MOCVD method, but other growth methods may be used. Also, in the example above,
Semiconductor distributed Bragg reflectors with different refractive indices 2
A linear composition gradient layer is used as an intermediate layer (a semiconductor layer having a refractive index (a band gap) between two types of semiconductor layers having different refractive indices) provided between the two types of semiconductor layers. In addition to this, a non-linear composition gradient layer whose composition changes non-linearly may be used, or a single layer or a plurality of layers having different refractive indexes may be used.

As described above, the p-type semiconductor distributed Bragg reflector has a problem that the resistance tends to be increased due to the influence of the potential barrier such as the spike at the semiconductor hetero interface such as the spike. The higher the difference in the forbidden band width between the semiconductor layers and the lower the doping concentration near the hetero interface, the more remarkable the increase in resistance. Conventionally, in order to reduce the effect of the hetero interface and reduce the resistance, the doping concentration of the hetero barrier buffer layer provided between two types of semiconductor layers such as the compositionally graded layer has been set to a high concentration. There is a problem that the optical absorption is increased due to the concentration, and the optical characteristics are deteriorated.

Further, in order to reduce light absorption, it is effective to reduce the impurity concentration, but conversely, the influence of the potential barrier at the hetero interface becomes remarkable. In order to reduce the influence of the potential barrier at the hetero interface, it is conceivable to reduce the difference in the forbidden band width of the two types of semiconductor layers forming the hetero interface, but the Bragg reflector causes a decrease in reflectance. In addition to increasing the number of layers, the region where the electric field intensity of light into the Bragg reflector is large exudes, and the thickness of the low-concentration doping region must be increased. There is a problem of increasing the resistance value. Further, even when the band gap is reduced, it is difficult to sufficiently reduce the resistance unless the composition gradient layer provided at the hetero interface is properly designed.

Further, for example, when the distributed Bragg reflector is used as a cavity mirror of a surface emitting laser device or the like, an oxide confinement layer formed by oxidizing Al (Ga) As is often provided in the Bragg reflector, Further, the oxide confinement layer is often provided in a low-concentration doping region near the active layer in order to enhance the constriction effect. In the periphery of the oxide confinement layer, current concentrates and the current path becomes smaller,
Even if the doping concentration is not low, it is very easy to increase the resistance.

On the other hand, in the semiconductor distributed Bragg reflector according to the first embodiment of the present invention, for example, a region having a low doping concentration as described above or an intermediate region between regions where the resistance is likely to be increased, such as the peripheral portion of the oxide confinement layer. By making the thickness of the layer (composition gradient layer) relatively thicker than other regions, the electric resistance in the above regions can be reduced very effectively.

For example, FIG. 5 shows that in the 0.98 μm band.
The resistivity of four pairs of p-type semiconductor distributed Bragg reflectors is
The Al composition of the low refractive index layer constituting the Ragg reflector is set as a parameter.
FIG. 3 is a diagram showing the composition gradient layer thickness as a data
The vertical axis represents the resistivity of each Bragg reflector at the hetero interface.
The value assuming that there is no effect, that is, simply
Value normalized by the resistivity determined by the resistance of Luk (standard
Resistance). Therefore, in FIG.
The normalized resistivity gradually increases to 1 as the influence of the surface is reduced.
Get closer. Here, a GaAs layer is used for the high refractive index layer.
And the doping concentration of the Bragg reflector is the absorption of light
5 × 10 in all areas to reduce ¹⁷cm^-3age
ing.

From FIG. 5, the resistivity of the semiconductor distributed Bragg reflector is lowered by decreasing the difference in Al composition, but it is drastically reduced by increasing the thickness of the intermediate layer (composition gradient layer). I know what to do.

As described above, in the case where the sufficiently thick composition gradient layer is provided, the Al composition difference is not significantly reduced,
It can be seen that the resistance can be reduced sufficiently.

Further, FIG. 6 shows 5 in the 0.98 μm band.
FIG. 6 is a diagram showing the reflectance of the pair of p-type semiconductor distributed Bragg reflectors with respect to the thickness of the intermediate layer (composition gradient layer) with the Al composition of the low refractive index layer constituting the Bragg reflector as a parameter. Here, the thickness of the GaAs layer, which is a high refractive index layer having a reflection wavelength of 0.98 μm and in which the composition gradient layer is not provided, is 69.5 nm, and AlAs and Al _0.8 Ga which are low refractive index layers. _0.2 As, Al _0.6 G
The thicknesses of a _0.4 As and Al _0.4 Ga _0.6 As are respectively
They are 80.2 nm, 77.5 nm, and 74.8 nm. It can be seen from FIG. 6 that the reflectance of the Bragg reflector is greatly reduced by reducing the Al composition of the low refractive index layer, and even if a thick intermediate layer (composition gradient layer) of about 60 nm is provided, It can be seen that the influence on the reflectance is smaller than the change in the Al composition of the low refractive index layer.

Therefore, in the semiconductor distributed Bragg reflector of the first embodiment, the Al composition of the low refractive index layer is so large that the reflectance is greatly affected as in the prior art even in the region where the doping is low. By providing a thick intermediate layer (composition gradient layer), it is possible to sufficiently reduce the resistance while maintaining a high reflectance even without reducing the value.
In addition, since the reflectance is high, the seeping of light into the semiconductor distributed Bragg reflector can be reduced, so that the number of layers in the low concentration region can be reduced, and the resistance of the semiconductor distributed Bragg reflector as a whole can be reduced. It can be kept low.
Further, since the influence on the reflectance is small, it is not necessary to increase the number of layers of the Bragg reflector, and it is possible to prevent the increase in resistance due to the increase in the number of layers.

When an oxide confinement layer such as a selective oxidation layer is provided in the region where the thickness of the intermediate layer (composition gradient layer) is increased in this way to confine the current, the current is concentrated due to the oxidation confinement. Since the resistance of the region to be reduced is reduced, the increase in resistance can be reduced.

As described above, in the first embodiment,
It is possible to obtain a semiconductor distributed Bragg reflector having excellent optical and electrical characteristics with low light absorption loss and electrical resistance.

Here, as a first embodiment of the present invention,
A p-type distributed Bragg reflector including two regions having different thicknesses and doping concentrations of the intermediate layers (composition gradient layers) of the distributed Bragg reflectors I and II has been shown. As the reflector, in addition to the one composed of two regions, a plurality of reflectors (three or more) are provided.
The intermediate layer may be composed of regions having different thicknesses and doping concentrations.

Second Embodiment In a second embodiment of the present invention, in the semiconductor distributed Bragg reflector of the first embodiment described above, an intermediate layer having a refractive index between two types of semiconductor layers having different refractive indexes. The difference in the forbidden band width of the two types of semiconductor layers in the region where the thickness of the layer (semiconductor layer) is large is the thickness of the intermediate layer (semiconductor layer) having the refractive index between the two types of semiconductor layers having different refractive indices Is smaller than the difference in the band gap between the two types of semiconductor layers in the thin region.

FIG. 7 is a diagram showing a specific example of the semiconductor distributed Bragg reflector according to the second embodiment of the present invention. The semiconductor distributed Bragg reflector shown in FIG. 7 is a p-type semiconductor distributed Bragg reflector having a design reflection wavelength of 0.98 μm, and is manufactured on a GaAs substrate by using the MOCVD method as a crystal growth method.

Further, the semiconductor distributed Bragg reflector of FIG. 7 has two regions I and II in which the thickness of the intermediate layer (composition gradient layer) is different, as in the p-type semiconductor distributed Bragg reflector of the first embodiment. However, in the second embodiment, the Al compositions of the low refractive index layers in the regions I and II are different from each other.

FIG. 8 shows the structure of one period in the p-type semiconductor distributed Bragg reflector I of FIG. 7, and FIG. 9 shows the one-period structure of the p-type semiconductor distributed Bragg reflector II of FIG.
The structure of the cycle is shown.

In the examples of FIGS. 8 and 9, as the low refractive index layer of the region I (Bragg reflector I), as shown in FIG.
l _0.8 Ga _0.2 As is used, while region II
As the low refractive index layer of (Bragg reflector II), p-AlAs is used as shown in FIG. A p-GaAs layer is used as the high refractive index layer in each of the regions I and II.

An intermediate layer (p-AlGaAs linear composition gradient layer) having a thickness of 60 nm is provided on each hetero interface of the Bragg reflector I, and each hetero interface of the Bragg reflector II has a thickness. A 30 nm intermediate layer (p-AlGaAs linear composition gradient layer) is provided.

Here, in the Bragg reflectors I and II,
The thickness of each layer constituting the Bragg reflector, including the intermediate layer (composition gradient layer), is adjusted so as to satisfy the phase condition of multiple reflection of the distributed Bragg reflector. Specifically, the p-Al _0.8 Ga _0.2 As layer in the Bragg reflector I has a thickness of 18.0 nm, and the p-GaAs layer has a thickness of 1
It is 1.8 nm. Also, p in the Bragg reflector II
The thickness of the -AlAs layer is 51.6 nm, and p-GaA is
The thickness of the s layer is 40.9 nm.

The semiconductor distributed Bragg reflector of FIG. 7 is designed so that light is incident from the region I (Bragg reflector I) side which is the surface of the substrate, and impurities in the region I (Bragg reflector I) are included. The doping concentration of, for example, about 5 × 10 ¹⁷ cm ^-3 and region II (Bragg reflector II)
The impurity concentration is relatively low with respect to the impurity doping concentration.

In the semiconductor distributed Bragg reflectors of FIGS. 7, 8 and 9, the low refractive index layer in the region I (Bragg reflector I) is p-Al _0.8 Ga _0.2 As, and the low refractive index layer A
Due to the decrease in the l composition (from AlAs to Al
_Due to the reduction to _0.8 Ga _0.2 As), generation of a potential barrier at the hetero interface can be suppressed.

Furthermore, in AlGaAs mixed crystals, the mobility of holes, which are carriers, generally tends to increase as the Al composition decreases. Therefore, in the Bragg reflector in which the influence of the potential barrier at the hetero interface is sufficiently reduced by the thick composition gradient layer as in the present invention, it is possible to effectively reduce the resistance due to the increased mobility. Is. Therefore, by reducing the Al composition of the low refractive index layer in the low-concentration doping region to the extent that the reflectance is not significantly reduced, it is possible to obtain a Bragg reflector with further reduced electrical resistance.

Thus, also in the second embodiment,
It is possible to obtain a semiconductor distributed Bragg reflector having a small light absorption loss and a low electric resistance, and having excellent optical and electrical characteristics.

Further, in the second embodiment, the thickness of the intermediate layer (composition gradient layer) in a part of the region of the semiconductor distributed Bragg reflector is made thicker than other regions, and further,
By making the difference in the forbidden band width of the two types of semiconductor layers forming the semiconductor distributed Bragg reflector in this region relatively smaller than that in the other regions, the electrical resistance is further improved as follows. It can be reduced.

That is, as described above, the cause of the high resistance at the hetero-interface is the potential barrier generated at the hetero-interface, and the greater the difference in the band gap between the semiconductor layers forming the hetero-interface, the more the hetero-interface becomes. The lower the doping concentration of, the higher the electrical resistance. For example, if the doping concentration of the semiconductor layer of the Bragg reflector, which is the incident side of light, is set to a low concentration in order to reduce the absorption loss of light, the effect of the hetero interface becomes remarkable due to the reduction of the doping concentration. Although it is easy to make resistance, as in the second embodiment, the electrical resistance is effectively reduced by making the thickness of the intermediate layer (composition gradient layer) in such a region thicker than other regions. In this case, the electrical resistance can be further effectively reduced by further reducing the difference in the forbidden band width of the semiconductor layers forming the semiconductor distributed Bragg reflector.

Further, for example, when the semiconductor distributed Bragg reflector is used as a resonator mirror of a surface emitting semiconductor laser device or the like, Al (Ga) is contained in the semiconductor distributed Bragg reflector.
An oxidized confinement layer formed by oxidizing As is often provided, and the oxidized constriction layer is often provided in a low-concentration doping region near the active layer in order to enhance the constriction effect. In the vicinity of the oxide confinement region, the current path becomes small, so that the resistance is likely to be very high even if the doping concentration is not low.

However, like the semiconductor distributed Bragg reflector of the second embodiment, the intermediate layer (composition gradient layer) in the region having a low doping concentration or the region where the resistance is likely to be increased, such as the peripheral portion of the oxide confinement layer, is formed. By increasing the thickness, it is possible to very effectively reduce the electrical resistance in this region, and at this time, further, the difference in the band gap of the semiconductor layers forming the semiconductor distributed Bragg reflector is reduced. By making it small, the electrical resistance can be reduced more effectively.

For example, by setting the thickness of the compositionally graded layer to 50 nm as shown in FIG. 5, the electric resistance can be reduced very effectively in any structure, but a semiconductor distributed Bragg reflector is formed. By further reducing the difference in the forbidden band width of the semiconductor layer, the resistance is further reduced.
Therefore, in order to further reduce the electric resistance, it is effective to reduce the difference in the band gap of the semiconductor layers. Further, the AlGaAs mixed crystal tends to have higher mobility of holes which are carriers as the Al composition is smaller, and therefore the resistance becomes lower by adopting the above configuration. However, as shown in FIG. 6, if the difference between the forbidden band widths is made too small, the influence on the reflectance becomes large, and the seeping of light into the semiconductor distributed Bragg reflector becomes remarkable,
By considering the reflectance and selecting the Al composition of the low refractive index layer so that the characteristics are not significantly deteriorated, it becomes possible to obtain a semiconductor distributed Bragg reflector having more excellent electrical characteristics.

In the second embodiment, the semiconductor distributed Bragg reflector can be manufactured by performing crystal growth on the GaAs substrate by the MOCVD method, but other growth methods may be used. Also, in the example above,
Semiconductor distributed Bragg reflectors with different refractive indices 2
A linear composition gradient layer is used as an intermediate layer (a semiconductor layer having a refractive index (a band gap) between two types of semiconductor layers having different refractive indices) provided between the two types of semiconductor layers. In addition to this, a non-linear composition gradient layer whose composition changes non-linearly may be used, or a single layer or a plurality of layers having different refractive indexes may be used.

Third Embodiment In the third embodiment of the present invention, in the semiconductor distributed Bragg reflector of the first or second embodiment, according to the electric field intensity of light in the semiconductor distributed Bragg reflector, It is characterized in that a plurality of intermediate layers (semiconductor layers) in the semiconductor distributed Bragg reflector have different thicknesses and doping concentrations.

More specifically, in the third embodiment, in the region where the electric field intensity of light in the semiconductor distributed Bragg reflector is large, the thickness of the intermediate layer (semiconductor layer) is increased and the doping concentration of impurities is increased. On the other hand, in the region where the electric field intensity of light is low, the thickness of the intermediate layer (semiconductor layer) is thin and the doping concentration of impurities is high.

FIG. 10 is a view showing a concrete example of the semiconductor distributed Bragg reflector of the third embodiment of the present invention. The semiconductor distributed Bragg reflector shown in FIG. 10 is a p-type semiconductor distributed Bragg reflector having a design reflection wavelength in the 0.98 μm band, and is manufactured on a GaAs substrate by using the MOCVD method as a crystal growth method.

The semiconductor distributed Bragg reflector shown in FIG. 10 has two regions I and II in which the thickness of the intermediate layer (composition gradient layer) is different, as in the p-type semiconductor distributed Bragg reflector of the first embodiment. In the third embodiment, the thickness of the intermediate layer (composition gradient layer) in region I and the doping concentration of impurities, and the intermediate layer in region II are configured by (two black reflectors I and II). The thickness of the (gradient composition layer) and the doping concentration of impurities differ depending on the electric field intensity of light. At this time, the thickness of each layer constituting the semiconductor distributed Bragg reflector, including the intermediate layer (composition gradient layer),
The semiconductor distributed Bragg reflector is adjusted to meet the multiple reflection phase condition.

Specifically, the semiconductor distributed Bragg reflector shown in FIG. 10 has a region I (Bragg reflector I) on the front surface side of the substrate.
It is designed so that light is incident from the side, and the area I
In (Bragg reflector I), p-Al _0.8 Ga _0.2 As is used as the low refractive index layer and p-GaAs is used as the high refractive index layer as shown in FIG. In addition, in FIG.
Is a diagram showing a structure of a semiconductor distributed Bragg reflector in the region I, the semiconductor distributed Bragg reflector I includes a _{p-GaAs / p-Al 0.8} Ga 0.2 As layer of the pair, as in Figure 11, each layer A basic structure made up of two compositionally graded layers provided between them constitutes one cycle, and in FIG. 10, this basic structure is repeatedly laminated for five cycles. FIG. 11 shows
In order to show in detail the change in thickness of the compositionally graded layer in the semiconductor distributed Bragg reflector of FIG. 10, a structure in which the above basic structure is stacked for two periods is shown.

FIG. 12 is a diagram showing the structure in the region II of the semiconductor distributed Bragg reflector shown in FIG.
In the region II (Bragg reflector II), p-Al _0.8 Ga _0.2 As is used as the low refractive index layer and p-GaAs is used as the high refractive index layer, as shown in FIG. In addition,
Similarly, FIG. 12 is a diagram showing a basic structure in a region II (Bragg reflector II), in which p-AlGaA is used in the region II.
An intermediate layer (composition gradient layer) having a thickness of 30 nm is provided between each of the s and p-GaAs layers, and in FIG.
The basic structure shown in FIG. 12 is one cycle, and 20 cycles are repeatedly stacked.

Here, in the region II (Bragg reflector II), each hetero interface is provided with an intermediate layer (composition gradient layer) having a thickness of 30 nm.

The doping concentration of impurities in the Al _0.8 Ga _0.2 As layer and the GaAs layer in the region II (Bragg reflector II) is set to about 1 × 10 ¹⁸ cm ^-3 . By setting the doping concentration of the intermediate layer (composition gradient layer) to be about the same as or slightly higher than this, the resistance can be more effectively lowered.

On the other hand, the doping concentration of the intermediate layer (composition gradient layer) in the region I (Bragg reflector I) is from the surface side where the electric field intensity of light is large toward the substrate side (arrow R in FIGS. 10 and 11). The concentration of the intermediate layer (composition gradient layer) is correspondingly adjusted from the surface side to the substrate side (see FIG. 1).
0, in the direction of arrow R in FIG. 11).

Specifically, in the region I (Bragg reflector I), the doping concentration on the surface side is, for example, 5 × 10 ^17.
cm ⁻³ , which is adjusted so as to gradually increase toward the substrate side (toward the doping concentration of the region II (Bragg reflector II)). The thickness of the intermediate layer (composition gradient layer) is also adjusted so as to gradually decrease from 60 nm on the surface side toward the substrate side (to 30 nm in the Bragg reflector II).

More specifically, an intermediate layer (composition gradient layer) having a thickness of 60 nm is provided on the outermost hetero interface of the region I (Bragg reflector I). ) Are sandwiched between the p-Al _0.8 Ga _0.2 As layers having a thickness of 18.
The thickness of the p-GaAs layer is 11.8 nm. The thickness of the intermediate layer (composition gradient layer) in the region I (Bragg reflector I) is calculated from the thickness 60 nm of the intermediate layer (composition gradient layer) to the region II (Bragg reflector II).
Toward the direction of, the thickness of the intermediate layer (composition gradient layer) of the region II (Bragg reflector II) becomes 30 nm,
The thickness is gradually reduced according to the doping concentration.
Along with this, p-Al _0.8 Ga _0.2 As layer, p-GaA
The film thickness of the s layer is gradually increasing. Here, the thickness of the p-Al _0.8 Ga _0.2 As layer is 51.6 nm and the thickness of the p-GaAs layer is 4 in the region II (Bragg reflector II).
It is 0.9 nm.

In the semiconductor distributed Bragg reflector of the third embodiment, in a region where the electric field intensity of incident light is large,
The thickness of the intermediate layer (composition gradient layer) is selected to prevent the resistance from becoming high due to the impurity doping concentration being low and the impurity doping concentration being low. The thickness of each layer is increased), thereby efficiently reducing the absorption loss without unnecessarily increasing the resistance and reducing the reflectance in the region I (Bragg reflector I). It is possible to obtain a Bragg reflector having excellent optical and electrical characteristics.

As described above, in the semiconductor distributed Bragg reflector of the third embodiment, a plurality of intermediate layers (composition gradient layers) having different thicknesses are provided in the Bragg reflector, and the thickness of the composition gradient layer is increased. And the doping concentration differs according to the electric field intensity of the light incident on the semiconductor distributed Bragg reflector (specifically, in the region where the electric field intensity is large, the composition gradient layer is thick, and the doping concentration is On the other hand, in the region where the electric field strength is small, on the other hand, in the region where the electric field strength is small, the composition gradient layer is thin and the doping concentration is high). Therefore, according to the electric field strength in the semiconductor distributed Bragg reflector, It is possible to efficiently reduce the light absorption loss and reduce the resistance.

In the semiconductor distributed Bragg reflector, the multiple reflection of the light wave due to the difference in the refractive index of each semiconductor layer is used, and the thickness of each semiconductor is such that the reflected waves are strengthened so that the reflected waves are strengthened. Has been selected for. Therefore, the reflection of the light wave does not occur only on the surface like a single reflecting mirror, but the light wave is gradually reflected while penetrating inside the semiconductor distributed Bragg reflector. The electric field strength is getting stronger.

Therefore, the doping concentration of the semiconductor distributed Bragg reflector in the region where the electric field intensity is large is set to a low concentration in accordance with the electric field intensity of light, and further the composition gradient layer is formed so that the resistance can be sufficiently lowered in accordance with the doping concentration. By determining the thickness, more effectively reduce the absorption loss of light,
It becomes possible to reduce the electric resistance. In this way, if the doping concentration of impurities is determined according to the electric field intensity of light, it is not necessary to set the doping concentration lower than necessary in the low doping concentration region provided to reduce absorption. It is possible to prevent the resistance from increasing and the composition gradient layer to reduce the reflectance.

However, also in the third embodiment, in the region near the incident surface where the electric field intensity of light is large, it is necessary to make the doping concentration sufficiently low, so that a sufficiently thick composition gradient layer is provided. It is important to reduce the resistance.

Further, for example, when the semiconductor distributed Bragg reflector is used as a cavity mirror of a surface emitting semiconductor laser device or the like, an oxidation confinement layer formed by oxidizing Al (Ga) As may be provided in the Bragg reflector. Furthermore, the oxide confinement layer is often provided in the low-concentration doping region near the active layer in order to enhance the constriction effect. In the vicinity of the oxide confinement region, the current path becomes small, so that the resistance is likely to be very high even if the doping concentration is not low.

As described above, in the vicinity of the oxide confinement layer, the current path is reduced due to the constriction, the resistance tends to be high, and the doping density is often low, so that the resistance becomes high. is there. However, if the composition gradient layer in such a region is made sufficiently thicker than the other regions as in the third embodiment, the resistance in the region where the current is concentrated due to the constriction is sufficiently reduced. As a result, the increase in resistance can be reduced.

As described above, the resistance of the Bragg reflector is increased by increasing the thickness of the intermediate layer (composition gradient layer) in the region where the doping concentration is low or the region where the resistance is likely to be increased, such as the peripheral portion of the oxide confinement layer. Can be reduced very effectively. Therefore, in the third embodiment, a semiconductor distributed Bragg reflector having excellent optical and electrical characteristics can be obtained.

In the third embodiment, as a semiconductor distributed Bragg reflector having different doping concentration and intermediate layer thickness, the thickness and doping concentration of the intermediate layer correspond to the electric field intensity of light from the light incident side. The semiconductor distributed Bragg reflector having a gradually thin and high concentration has been described above. However, in the first and second embodiments, a semiconductor distributed Bragg reflector including two regions having different intermediate layer thicknesses is used. , Make the concentration of doping in the thick region of the intermediate layer low,
The doping concentration in the thin region of the intermediate layer is set to a high concentration, and the thickness and the doping concentration of the intermediate layer are made different. Similarly, it is possible to effectively reduce the light absorption loss and the electrical resistance. Is something that can be done.

In the third embodiment, the semiconductor distributed Bragg reflector can be produced by crystal growth on the GaAs substrate by the MOCVD method, but other growth methods may be used. Also, in the example above,
Semiconductor distributed Bragg reflectors with different refractive indices 2
A linear composition gradient layer is used as an intermediate layer (a semiconductor layer having a refractive index (a band gap) between two types of semiconductor layers having different refractive indices) provided between the two types of semiconductor layers. In addition to this, a non-linear composition gradient layer whose composition changes non-linearly may be used, or a single layer or a plurality of layers having different refractive indexes may be used.

Fourth Embodiment A fourth embodiment of the present invention is the semiconductor distributed Bragg reflector according to any one of the first to third embodiments, wherein the design reflection wavelength of the semiconductor distributed Bragg reflector is 1.1 μm. It is characterized by longer waves than.

FIG. 13 is a diagram showing a specific example of the semiconductor distributed Bragg reflector of the fourth embodiment. The semiconductor distributed Bragg reflector shown in FIG. 13 is a p-type semiconductor distributed Bragg reflector having a design reflection wavelength in the 1.3 μm band, and is manufactured on a GaAs substrate by MOCVD as a crystal growth method.

Further, the semiconductor distributed Bragg reflector of FIG. 13 has two regions I and II in which the thickness of the intermediate layer (composition gradient layer) is different, like the p-type semiconductor distributed Bragg reflector of the first embodiment. It is composed by.

Here, FIG. 14 shows one cycle of stacking in the p-type semiconductor distributed Bragg reflector I of FIG. 13. Referring to FIG. 13, in the Bragg reflector I,
P-Al _0.8 Ga _0.2 As is used as the low refractive index layer,
P-GaAs is used as the high refractive index layer. In addition, a thickness of 80 nm is provided between each of these semiconductor layers.
The intermediate layer (p-AlGaAs linear composition gradient layer) is provided in the semiconductor distributed Bragg reflector shown in FIG.
The structure shown in 4 is defined as one cycle, and four cycles are stacked.

Similarly, FIG. 15 shows one cycle of stacking in the p-type semiconductor distributed Bragg reflector II of FIG. 13, and in the Bragg reflector II, as the low refractive index layer p-
AlAs is used and p-GaAs is used as the high refractive index layer. Further, an intermediate layer (p-AlGaAs linear composition gradient layer) having a thickness of 50 nm is provided between each of these semiconductor layers. In the semiconductor distributed Bragg reflector shown in FIG. 13, the structure shown in FIG. And 20 cycles are stacked.

The semiconductor distributed Bragg reflector shown in FIG. 13 is designed so that light is incident from the region I (Bragg reflector I) side which is the surface of the substrate, and the doping concentration of impurities in the region I is For example, 5 × 10 ¹⁷ cm
^-3 , which is relatively low with respect to the doping concentration in the region II.

The design reflection wavelength of the semiconductor distributed Bragg reflector shown in FIG. 13 is 1.3 μm, which is a long wavelength band, and is 0.9
It has a longer wave than the Bragg reflector in the 8 μm band.
It is known that light absorption between valence bands becomes very remarkable in such a long wavelength band. For example, the document “IEEE J. Quantum Electron. Vol.33 No.8 1997 pp1
369 ”, the optical absorption coefficient of GaAs for light in the 1.3 μm band is about twice that of the 0.98 μm band, and 1.5
It is described that it becomes about 3 times in the μm band. As described above, the light absorption becomes very remarkable for the light with the wavelength longer than 1.1 μm, and it is very necessary to reduce the light absorption in order to obtain a highly efficient semiconductor distributed Bragg reflector. is important.

In the semiconductor distributed Bragg reflector of FIG.
The doping concentration of the region I on the light incident side is relatively low, and the light absorption loss is small. Further, since the reflection wavelength is long, the thickness of the layer constituting the semiconductor distributed Bragg reflector is thicker than that of the conventional surface emitting laser element in the 0.98 μm band. For this reason,
Even when a thick intermediate layer (composition gradient layer) is provided, the influence on the decrease in reflectance is small. Further, by providing the thick intermediate layer (composition gradient layer), the effect of smoothing the potential barrier at the hetero interface becomes very high. Therefore, even when there is a large difference in band gap between the two types of semiconductor layers that form the semiconductor distributed Bragg reflector, the effect of reducing the electrical resistance can be sufficiently obtained by the intermediate layer (composition gradient layer). Therefore, the exudation of light to the semiconductor distributed Bragg reflector can be suppressed to a small level, and the thickness of the low concentration doping region can be reduced. Further, the number of layers of the semiconductor distributed Bragg reflector can be reduced, and the electric resistance can be suppressed low.

As described above, in the fourth embodiment, a semiconductor distributed Bragg reflector in a long wavelength band having a small light absorption loss and a low electric resistance and excellent characteristics can be obtained.

More specifically, the valence band absorption, which is the cause of the light absorption of the p-type semiconductor distributed Bragg reflector, is
Electrons absorb light and are caused by the transition from spin-orbit split-off band of valence band to heavy hole and light hole bands, and the energy difference between these levels is small. The absorption becomes remarkable. Therefore, in the 1.3 μm and 1.5 μm bands, which are important in optical communication, etc., the absorption is much larger than that in the 0.85 μm and 0.98 μm bands of the laser devices and the like that have been fabricated on the GaAs substrate. There is a loss. That is, since the p-type semiconductor distributed Bragg reflector according to the prior art has a large absorption coefficient, a p-type semiconductor distributed Bragg reflector having excellent characteristics having both low resistance and small absorption loss is obtained. Difficult to do.

However, in the structure of any one of the first to third embodiments of the present invention, as described above, the light intensity is large in the region where the light absorption is remarkable, that is, in the semiconductor distributed Bragg reflector. It is possible to reduce the light absorption of the area without increasing the resistance. Further, as a semiconductor distributed Bragg reflector having a reflection wavelength longer than 1.1 μm of the fourth embodiment, for example, 1.3.
The thickness of the GaAs layer, which is a high refractive index layer, in the structure having no composition gradient layer in the μm band is 95.2 nm,
The thickness of AlAs which is a low refractive index layer is 111.6 nm,
It becomes thicker as the wavelength becomes longer. In this way, the longer the reflection wavelength is, the smaller the ratio of the compositionally graded layer in the semiconductor distributed Bragg reflector becomes, and the influence on the reflectance can be reduced. In other words, it is possible to provide a thicker composition gradient layer than the conventional 0.85 μm band and 0.98 μm band semiconductor distributed Bragg reflectors while maintaining a high reflectance. The thicker the composition graded layer,
Since the effect of smoothing the potential barrier of the hetero interface is high, it is possible to sufficiently reduce the electric resistance.

In FIG. 16, the reflection wavelength is 1.3 μm.
It is a figure which shows the reflectance with respect to the thickness of a composition gradient layer about Al composition of a low refractive index layer as a parameter about a semiconductor distributed Bragg reflector of a pair. In FIG. 16, the high refractive index layer of the semiconductor distributed Bragg reflector is GaAs.
AlA that is a low refractive index layer when a composition gradient layer is not provided
s, Al _0.8 Ga _0.2 As, Al _0.6 Ga _0.4 As, Al
The thickness of each _0.4 Ga _0.6 As layer is 111.6 n.
m, 108.2 nm, 104.8 nm, 101.5 nm
The thickness of the GaAs layer, which is the high refractive index layer, is 95.2 nm as described above. Referring to FIG.
As in the case of the 98 μm band semiconductor distributed Bragg reflector, it can be seen that the influence on the reflectance is relatively small even when a thick composition gradient layer that is mostly a composition gradient layer is provided.

Therefore, in the semiconductor distributed Bragg reflector having such a long wavelength band as the reflection wavelength, the conventional 0.98 μm
Compared to the m-band semiconductor distributed Bragg reflector, it has less effect on the reflectivity of the compositionally graded layer, maintains the high reflectivity in the low-concentration doped region, and reduces the light leakage in the semiconductor distributed Bragg reflector. It becomes easy to do.

Therefore, the semiconductor distributed Bragg reflector of the fourth embodiment can reduce the number of layers in the low-concentration doped region, the Bragg reflector as a whole has low resistance, and the low-concentration region has a low resistance. Since the reflectance is also sufficiently high, it is not necessary to increase the number of layers of the semiconductor distributed Bragg reflector, and similarly the resistance of the Bragg reflector as a whole can be suppressed low.

As described above, in the semiconductor distributed Bragg reflector having a wavelength longer than the 1.1 μm band, the resistance can be remarkably low.

Further, as described in the first to third embodiments, when the Bragg reflector is used as a cavity mirror of a surface emitting semiconductor laser device or the like, Al (Ga) As is contained in the Bragg reflector. An oxidized constriction layer formed by oxidation is often provided, and the oxidized constriction layer is often provided in a low concentration doping region near the active layer in order to enhance the constriction effect. If the composition gradient layer in the region around the oxidation confinement layer is made sufficiently thicker than the other regions, the resistance in the region where the current is concentrated due to the constriction is sufficiently reduced, so that the increase in the resistance is reduced. be able to.

As described above, in the fourth embodiment,
Light absorption loss and electrical resistance are low enough,
Long wavelength band with excellent electrical characteristics (reflection wavelength is 1.1μ
It is possible to obtain a semiconductor distributed Bragg reflector in a band longer than m.

In the fourth embodiment, the semiconductor distributed Bragg reflector can be produced by crystal growth on the GaAs substrate by the MOCVD method, but other growth methods such as the MBE method are used. May be. Further, in the above-mentioned example, the intermediate layer (refractive index between two semiconductor layers having different refractive indexes (forbidden band width) which is provided between the two semiconductor layers having different refractive indexes which constitute the semiconductor distributed Bragg reflector is used. Although a linear composition gradient layer is used as the semiconductor layer having a), a non-linear composition gradient layer whose composition changes nonlinearly may be used as the intermediate layer. You may use what was comprised by the different single layer or multiple layers.

Fifth Embodiment A surface emitting semiconductor laser device can be constructed using the semiconductor distributed Bragg reflector of any of the first to fourth embodiments described above.

The fifth embodiment of the present invention is the first to fourth embodiments.
Is a surface emitting semiconductor laser device using the semiconductor distributed Bragg reflector according to any one of the above-mentioned embodiments as a resonator mirror.

FIG. 17 is a diagram showing a specific example of the surface emitting semiconductor laser device of the fifth embodiment. The surface-emitting semiconductor laser device of FIG. 17 has a GaInNAs active layer of 1.3.
This is a μm band surface emitting laser device, and crystal growth is performed by MOCVD method using trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), and arsine (AsH ₃ ) gas as raw materials. At this time, dimethylhydrazine (DMHy) is used as the nitrogen source of the active layer. Further, CBr ₄ is used as the p-type dopant and H ₂ Se is used as the n-type dopant.

That is, in the surface emitting semiconductor laser device of FIG. 17, after forming an n-GaAs buffer layer on an n-GaAs substrate, 36 pairs of n-type semiconductor distributed Bragg reflectors having AlAs / GaAs as a pair, A GaAs resonator spacer layer, a GaInNAs / GaAs multiple quantum well structure (active layer), a GaAs resonator spacer layer, and a p-type semiconductor distributed Bragg reflector are sequentially formed.

Here, the p-type semiconductor distributed Bragg reflector
Is Al_0.8Ga_0.24 pairs of As / GaAs pair
p-type semiconductor distributed Bragg reflector I (region I) and Al
_0.8Ga_{0 .2}18 pairs of p-type halves with one pair of As / GaAs
Consists of a conductor distributed Bragg reflector II (region II)
The optical field strength is close to the active layer, which is the oscillation region.
Bragg reflector I (region I) located in a large region
The doping concentration is 5 × to reduce the absorption loss of the oscillation light.
10¹⁷cm^-3Degree and Dopi in Bragg Reflector II
Concentration 1 × 10¹⁸cm^-3To a relatively low concentration
The doping is applied so that

The p-type semiconductor distributed Bragg reflector I
At each hetero interface in (region I), a thickness of 80 n is obtained by linearly changing the Al composition from one semiconductor layer to the other semiconductor layer.
m linear composition gradient layers (intermediate layers) are provided. Similarly, each hetero interface of the p-type semiconductor distributed Bragg reflector II (region II) is also provided with a linear composition gradient layer (intermediate layer) having a thickness of 50 nm.

In a surface emitting semiconductor laser device having a long wave such as 1.3 μm band, the reflectance is not significantly lowered,
It is possible to provide such a thick composition gradient layer (intermediate layer).

Further, in the surface emitting semiconductor laser device of FIG. 17, an AlAs selective oxidation layer having a thickness of 30 nm is provided at the interface of the p-type semiconductor distributed Bragg reflector I (region I) which is the first pair from the active layer side. ing. Further, the GaAs layer on the outermost surface of the p-type semiconductor distributed Bragg reflector has a high doping concentration and is also used as a contact layer.

Here, the thickness of each layer constituting the p-type semiconductor distributed Bragg reflector and the n-type semiconductor distributed Bragg reflector is distributed in the same manner as in the first embodiment, including the composition gradient layer (intermediate layer). It is adjusted so as to satisfy the phase condition of multiple reflection of the Bragg reflector, and the thickness of the Al _0.8 Ga _0.2 As layer in contact with the AlAs selective oxidation layer is also adjusted. Further, the phase change of the oscillation light in the active layer and the two cavity spacer layers of this surface emitting semiconductor laser device is 2
It is equal to π and forms a λ cavity. Further, the active layer is arranged at the center of the λ cavity, that is, at the position serving as the antinode of the standing wave of light.

The surface emitting semiconductor laser device of FIG. 17 is manufactured as follows after forming the above-mentioned laminated structure (element laminated film).

That is, after forming the above-mentioned laminated structure, the element region is left by the known photolithography and dry etching method, and the surface of the p-GaAs contact layer is changed to the n semiconductor distributed Bragg reflector. GaAs in contact
Each layer up to the middle of the resonator spacer layer is removed by etching. At this time, the mesa that becomes the element portion is 30 μm × 30
It has a square mesa shape of μm.

Next, heated pure water is heated in an atmosphere obtained by bubbling with nitrogen gas, and the selective oxidation is performed from the lateral direction from the etching side surface of the AlAs selective oxidation layer toward the central portion of the element to obtain the current. Provide a narrowing structure. Here, the size of the region serving as the current passage is 5 μm × 5 μm.

Next, the mesa portion is filled with an insulating resin such as polyimide, and then the electrode material is vapor-deposited and the lift-off method is used to form a p-shaped opening having a light emitting portion on the upper surface of the device.
A mold electrode is formed. Next, an n-type electrode is formed on the back surface of the GaAs substrate to manufacture the surface emitting semiconductor laser device shown in FIG.

In the surface emitting semiconductor laser device shown in FIG. 17, the doping concentration of the p-type semiconductor distributed Bragg reflector is reduced particularly in the vicinity of the active layer where the intensity of oscillation light is high.
As a result, the loss due to light absorption is reduced, whereby the slope efficiency of the element can be improved and the oscillation threshold current can be reduced. Further, the thickness of the intermediate layer (composition gradient layer) in the p-type Bragg reflector I (region I) is made thicker than the thickness of the intermediate layer (composition gradient layer) in the p-type Bragg reflector II (region II). With the provision, the potential barrier at the hetero interface is sufficiently smoothed even though the doping concentration is low, and it is possible to prevent an increase in resistance value and an increase in operating voltage. Therefore, the heat generation of the element does not increase, the output is not reduced by new heat generation, and conversely, the light absorption loss is reduced, so that it is possible to obtain a higher output than the conventional one.

In the surface emitting semiconductor laser device of FIG. 17, the active layer material is GaInNAs, and GaAs is used.
A surface emitting semiconductor laser device that oscillates at 1.3 μm can be formed by using a semiconductor distributed Bragg reflector having excellent characteristics of Al (Ga) As / GaAs on the substrate.
The GaInNAs mixed crystal has a large amount of conduction band discontinuity with the GaAs resonator spacer layer and has a high effect of confining electrons in the active layer, so that stable oscillation can be obtained even at high temperatures. Further, the 1.3 μm band corresponds to the zero dispersion band of the silica fiber, and by using the same single mode fiber,
High-speed communication is possible. From this, the surface emitting semiconductor laser device of FIG. 17 can easily realize a high-speed communication system by combining with the quartz single mode fiber.

In the above example, the surface emitting semiconductor laser device manufactured by crystal growth on the n-type semiconductor substrate has been described. However, as the surface emitting semiconductor laser device,
In addition to this, it may be manufactured by performing crystal growth on a p-type semiconductor substrate.

FIG. 18 shows an example of a surface emitting semiconductor laser device manufactured by crystal growth on a p-type semiconductor substrate. The surface emitting semiconductor laser device of FIG.
It is manufactured by performing crystal growth on a GaAs substrate by the MOCVD method similarly to the surface emitting semiconductor laser device of FIG.

That is, in the surface emitting semiconductor laser device of FIG. 18, first, after crystal growth of a p-GaAs buffer layer on a p-GaAs substrate, Al _0.8 Ga _0.2 As /
Crystal growth of 32 pairs of p-type semiconductor distributed Bragg reflectors II (region II) with GaAs as one pair was performed, and then Al was grown.
Five pairs of p-type semiconductor distributed Bragg reflectors I (region I) having _0.5 Ga _0.5 As / GaAs as a pair, a GaAs resonator spacer layer, a GaInNAs / GaAs multiple quantum well active layer, a GaAs spacer layer, and Al _0.8 Ga _0.2. As / G
24 pairs of n-type semiconductor distributed Bragg reflectors, each pair consisting of aAs, are produced by crystal growth.

In the surface emitting semiconductor laser device of FIG. 18, similar to the surface emitting semiconductor laser device of FIG. 17, the electrical resistance is reduced at each hetero interface of the p-type semiconductor distributed Bragg reflector II (region II). And a linear composition gradient layer (intermediate layer) having a thickness of 80 nm, and a linear composition gradient layer (intermediate layer) having a thickness of 80 nm at each hetero interface of the p-type semiconductor distributed Bragg reflector I (region I). ) Is provided so as to satisfy the phase condition of multiple reflection of the semiconductor distributed Bragg reflector. At the hetero interface of Al _0.8 Ga _0.2 As / GaAs closest to the active layer, an AlAs selective oxidation layer is similarly provided in consideration of the phase condition.

After the crystal growth, the surface emitting semiconductor laser device of FIG. 18 has the same structure as the surface emitting semiconductor laser device of FIG.
Dry etching, selective oxidation, filling with an insulating resin, and electrode formation are performed. However, in the dry etching process, the AlAs in the p-type semiconductor distributed Bragg reflector is
In order to oxidize the selective oxidation layer, the p-type semiconductor distributed Bragg reflector is partially etched.

The surface emitting semiconductor laser device of FIG. 18 is also shown in FIG.
Similar to the surface emitting semiconductor laser device, the absorption threshold of light by the p-type semiconductor distributed Bragg reflector is reduced, so that the oscillation threshold current is reduced and the slope efficiency can be improved. Further, since the increase of the element resistance is prevented, the operating voltage is low and a high output can be obtained.

By combining the surface emitting semiconductor laser device of FIG. 18 with a quartz single mode fiber, a high speed communication system can be easily realized.

As described above, in the surface emitting semiconductor laser device of the fifth embodiment, the doping concentration of the p-type semiconductor distributed Bragg reflector in the region near the active layer where the electric field intensity of the oscillation light is large is separated from the active layer. By making the doping concentration lower than the doping concentration in the region where the electric field intensity of the oscillation light is relatively small, it is possible to reduce the absorption loss of light, improve the slope efficiency, and reduce the oscillation threshold current.

Further, in the present invention, the thickness of the compositionally graded layer in the low-concentration doped region of the p-type Bragg reflector is made thicker than that in the other high-concentration doped regions, so that the hetero interface of the low-concentration doped region is formed. The potential barrier is sufficiently smoothed, and light absorption loss can be reduced without increasing the resistance value. At this time, even if the thickness of the composition gradient layer is made sufficiently thick as shown in FIG. 6, there is little influence on the reflectance, and therefore a sufficiently thick composition gradient layer can be provided. Therefore, in order to reduce the electric resistance in the low concentration region as in the conventional case,
It is not necessary to significantly reduce the Al composition, and it is possible to maintain a high reflectance in the low concentration doping region. Therefore, the exudation of light into the Bragg reflector is reduced,
Since the thickness of the lightly doped region can be reduced, it is possible to prevent an increase in resistance. In addition, since the number of Bragg reflectors stacked can be reduced, an increase in resistance can be prevented.

Further, in the surface emitting semiconductor laser device, an oxide confinement layer formed by oxidizing Al (Ga) As is often provided in the semiconductor distributed Bragg reflector, and the oxide confinement layer is used to enhance the constriction effect. Often, it is provided in a low-concentration doping region close to the active layer. In the vicinity of the oxide confinement layer, the current is concentrated and the current path becomes small, so that there is a problem that the resistance tends to be very high even if the doping concentration is not low.

However, like the semiconductor distributed Bragg reflector of the present invention, the thickness of the composition gradient layer in the region where the doping concentration is low as described above or the region where the resistance is likely to be increased, such as the peripheral portion of the oxide confinement layer, is set. By making the thickness relatively thicker than other regions, it is possible to very effectively reduce the resistance in the above regions.

Therefore, as compared with the conventional device, the operating voltage and the heat generation of the device can be reduced, the saturation output due to heat is high, and the absorption loss is reduced, so that the slope efficiency is improved and the oscillation threshold current is increased. It is possible to obtain a surface emitting semiconductor laser device with reduced

As described above, the surface-emitting semiconductor laser device of the fifth embodiment reduces the absorption loss of the oscillation light in the surface-emitting semiconductor laser device and increases the slope efficiency without increasing the device resistance. The oscillation threshold current is reduced, higher output operation is possible, and power conversion efficiency is further improved.

In the surface emitting semiconductor laser device of the fifth embodiment, the group III material of the active layer is Ga, I.
Any or all of n, and the group V material of the active layer can be any or all of As, N, and Sb.

The active layer made of these materials is GaAs.
A DBR made of an AlGaAs-based material that can be grown on a substrate and has excellent characteristics in terms of reflectance, thermal conductivity, and process control (crystal growth and selective oxidation of Al (Ga) As mixed crystal) The surface emitting semiconductor laser device used can be obtained. In addition, by using these materials for the active layer, oscillations of wavelengths longer than 1.1 μm including 0.85 μm band and 0.98 μm band, and 1.3 μm band and 1.5 μm band which are important for optical fiber communication. You can get the light.

Specifically, high-speed optical communication can be realized by combining a surface-emitting semiconductor laser device having a wavelength of 1.3 μm band and a quartz single mode laser. Further, if DWDM using a 1.5 μm band element is used, it becomes possible to realize large capacity communication.

At this time, in particular, among the above-mentioned active layer materials, the GaInN (Sb) As mixed crystal material can obtain an oscillation of 1.1 μm or more and, in addition, can be used for the GaAs layer which becomes the carrier confinement layer. , The amount of band discontinuity in the conduction band of the GaInN (Sb) As layer is large and the overflow of electrons can be reduced, so that stable oscillation can be obtained up to a high temperature.

In addition to these, in the surface-emitting semiconductor laser device of the present invention, as described above, the absorption efficiency of light is small and the resistance is low as compared with the conventional device, so that the slope efficiency is improved and the oscillation is improved. The threshold current can be reduced. Moreover, since the resistance is low, the saturation output is high and a high output can be obtained. Further, the power conversion efficiency is high and the low power consumption is small. As described above, it is possible to provide a surface emitting semiconductor laser device suitable for optical communication and optical transmission.

In each of the above embodiments, the AlGaAs mixed crystal has been described as the material of the semiconductor distributed Bragg reflector, but it is also possible to use the GaInP mixed crystal in addition to this. Since the GaInP mixed crystal can be lattice-matched with the GaAs substrate and has a band gap that is larger than that of the GaAs compound semiconductor (the refractive index is smaller than that of the GaAs compound semiconductor), it is used as a low refractive index layer instead of the AlGaAs mixed crystal. be able to. Further, the GaInP mixed crystal semiconductor has selectivity in the wet etching with respect to the AlGaAs mixed crystal semiconductor layer and can be used also as an etching stop layer when forming a mesa by the wet etching. In the surface emitting laser device, etching controllability can be improved.

Sixth Embodiment A sixth embodiment of the present invention is a surface emitting laser array constituted by the surface emitting semiconductor laser device according to the fifth embodiment.

FIG. 19 is a diagram showing a specific example of the surface emitting laser array according to the sixth embodiment. The surface-emitting laser array shown in FIG. 19 includes the surface-emitting semiconductor laser device of the fifth embodiment.
It is a monolithic laser array in which 3 × 3 pieces are dimensionally integrated. In the surface-emission laser array of FIG. 19, p-electrode wirings are individually provided in order to drive each surface-emission semiconductor laser device independently. The surface emitting laser array of FIG. 19 is manufactured by the same procedure and method as those in the fifth embodiment.

In the surface-emission laser array of FIG. 19, the individual surface-emission semiconductor laser elements forming this surface-emission laser array have a small light absorption loss and a low resistance. Since the efficiency is high, a highly efficient surface emitting laser array can be obtained.

That is, as described above, the surface emitting semiconductor laser device of the present invention can have a large slope efficiency, a low oscillation threshold current, a high power conversion efficiency, and low power consumption. Therefore, the surface emitting laser array constituted by such a surface emitting semiconductor laser device of the present invention has a high power conversion efficiency as a whole array, which is extremely efficient.

Further, by forming the surface emitting laser array, parallel optical transmission is facilitated, and it is possible to perform optical transmission and optical communication with a larger capacity. Further, when the surface emitting laser array oscillating in the 1.3 μm band is constituted by the above-mentioned active layer material of the surface emitting semiconductor laser device of the present invention, high speed parallel transmission and communication become possible. Similarly, when a laser array that oscillates in the vicinity of the 1.5 μm band is configured, WDM, DWDM, or other wavelength multiplexing communication is possible, and surface emission that enables higher speed, large capacity optical transmission, and optical communication. A laser array can be provided.

Seventh Embodiment A seventh embodiment of the present invention is a surface emitting laser module using the surface emitting semiconductor laser device of the fifth embodiment or the surface emitting laser array of the sixth embodiment. is there.

FIG. 20 is a diagram showing a specific example of the surface emitting laser module according to the seventh embodiment. The surface emitting laser module of FIG. 20 is configured by mounting a one-dimensional monolithic surface emitting laser array, a microlens array, and a fiber array (quartz single mode fiber) on a silicon substrate.

Here, the surface-emission laser array is provided with the surface-emission laser array of the sixth embodiment so as to face the fiber. This surface-emission laser array is provided with a silicon substrate through a microlens array. It is coupled with the quartz single mode fiber mounted in the V groove formed in the above. The oscillation wavelength of this surface emitting laser array is 1.3 μm.
This is a band, and high-speed optical parallel transmission can be performed by using a quartz single-mode fiber.

Further, by using the surface emitting laser array of the sixth embodiment as the light source of the surface emitting laser module of the seventh embodiment, the light absorption loss is small,
Further, it is possible to obtain a surface emitting laser module having low resistance and high power conversion efficiency.

As described above, in the surface-emission laser module of the seventh embodiment, the surface-emission semiconductor laser device of the fifth embodiment or the sixth embodiment having a low resistance with reduced light absorption loss is provided.
The surface emitting laser array according to the embodiment is used, and thus, it is possible to provide a surface emitting laser module having high slope efficiency, low oscillation threshold current, high power conversion efficiency, and low power consumption.

Particularly, in the surface emitting laser module in which the 1.3 μm band surface emitting laser using the GaInNAs mixed crystal semiconductor as the active layer material and the quartz single mode fiber are combined, the 1.3 μm band corresponds to the zero dispersion band of quartz. The structure is very suitable for high-speed modulation. By using this surface emitting laser module, high-speed, large-capacity optical communication,
It becomes possible to perform optical transmission.

In addition, in the surface emitting laser module using the surface emitting semiconductor laser element oscillating in the 1.5 μm band,
WDM communication such as DM and DWDM is possible.
It enables high-speed, large-capacity optical transmission and optical communication. As described above, it is possible to provide a surface emitting laser module having excellent characteristics and capable of high-speed, large-capacity optical transmission and optical communication.

Eighth Embodiment The eighth embodiment of the present invention is a surface emitting semiconductor laser device according to the fifth embodiment, a surface emitting laser array according to the sixth embodiment, or a seventh embodiment. It is an optical interconnection system configured by using the surface emitting laser module.

FIG. 21 is a diagram showing a parallel optical interconnection system as an example of the eighth embodiment. In the optical interconnection system of FIG. 21, the device 1 and the device 2 are connected using an optical fiber array (quartz single mode fiber array). Here, the device 1 on the transmitting side is provided with a surface-emission laser module including the surface-emission laser array according to the seventh embodiment and a drive circuit for the same. In addition, the device 2 on the receiving side is
A photodiode array module and a signal detection circuit are provided.

In the optical interconnection system of FIG. 21, by using the surface emitting laser module of the seventh embodiment, absorption loss of oscillation light is small, resistance is low, and power conversion efficiency can be increased. An optical transmission system with low power consumption and excellent characteristics can be obtained.
Further, by using the surface emitting laser module using the surface emitting laser array of the present invention in which GaInNAs is the active layer, a highly reliable interconnection system that is stable against environmental temperature changes is constructed. can do.

In the above example, the parallel optical interconnection system is described as an example.
It is also possible to configure a serial transmission system using a single element as in the above embodiment. Further, as the optical interconnection system, in addition to the surface emitting laser module of the seventh embodiment, the surface emitting semiconductor laser device and the surface emitting laser array of the fifth and sixth embodiments may be used. it can. Further, in addition to the optical interconnection system between devices, it can be applied to optical interconnection between boards, between chips, and within a chip.

As described above, the eighth embodiment is the surface emitting semiconductor laser device of the fifth embodiment, the surface emitting laser array of the sixth embodiment, or the surface emitting laser of the seventh embodiment. An optical interconnection system configured by using a module, wherein the optical interconnection system includes a surface emitting semiconductor laser device with a low absorption loss, a surface emitting laser array, or a surface emitting laser. Since the module is used, an optical interconnection system with high power conversion efficiency and low power consumption can be constructed.

In particular, an optical interconnection system composed of a surface emitting laser module in which a 1.3 μm band surface emitting laser using a GaInNAs mixed crystal semiconductor as an active layer material and a quartz single mode fiber are combined has a 1.3 μm band Since it corresponds to the zero-dispersion band of quartz, it has a configuration that is very suitable for high-speed modulation, and high-speed, large-capacity optical transmission is possible. Further, the surface-emitting semiconductor laser device using the GaInNAs mixed crystal semiconductor as the active layer can stably oscillate up to high temperature even with changes in environmental temperature, etc., and therefore has very high reliability in optical interconnection. A system can be provided.

As described above, in the eighth embodiment, the surface-emission semiconductor laser device according to the fifth embodiment, the surface-emission laser array according to the sixth embodiment, or the surface-emission laser according to the seventh embodiment. By using the module, it is possible to provide an optical interconnection system capable of high-speed and large-capacity optical transmission, high power conversion efficiency, and high reliability.

Ninth Embodiment The ninth embodiment of the present invention is a surface emitting semiconductor laser device according to the fifth embodiment, a surface emitting laser array according to the sixth embodiment, or a seventh embodiment. Is an optical communication system configured by using the surface emitting laser module.

FIG. 22 is a diagram showing an optical LAN system as an example of the optical communication system of the ninth embodiment. Figure 2
The optical LAN system 2 includes the surface emitting semiconductor laser device according to the fifth embodiment, the surface emitting laser array according to the sixth embodiment, or the surface emitting laser module according to the seventh embodiment. There is.

That is, in the optical LAN system of FIG. 22, the light source for optical transmission between the server and the core switch and / or the light source for optical transmission between the core switch and each switch and / or the switch The surface emitting semiconductor laser device of the fifth embodiment or the surface emitting laser array of the sixth embodiment is used as a light source for optical transmission with each terminal.
Alternatively, the surface emitting laser module of the seventh embodiment is used. In addition, quartz single mode fibers or multimode fibers are used to couple the devices. Examples of the physical layer of such an optical LAN include Gigabit Ethernet (registered trademark) such as 1000BASE-LX.

In the optical LAN system of FIG. 22, the surface emitting semiconductor laser device of the fifth embodiment or the surface emitting laser array of the sixth embodiment is used as the light source for optical transmission, or
By using the surface emitting laser module according to the seventh embodiment, an absorption loss of oscillation light is small, resistance is low, power conversion efficiency can be further increased, and an optical transmission system with low power consumption is provided. be able to. Furthermore, Ga
In the surface emitting laser of the present invention using InNAs as an active layer,
It is possible to stably oscillate even with changes in driving conditions such as environmental temperature, and to configure a highly reliable optical communication system.

As described above, the ninth embodiment is the surface emitting semiconductor laser device of the fifth embodiment, the surface emitting laser array of the sixth embodiment, or the surface emitting laser of the seventh embodiment. An optical communication system configured by using a module, wherein the optical communication system includes a low-resistance surface-emitting semiconductor laser device with reduced light absorption loss, or
Since the surface emitting laser array or the surface emitting laser module is used, an optical communication system with high power conversion efficiency and low power consumption can be constructed.

In particular, in an optical communication system composed of a surface emitting laser module in which a 1.3 μm band surface emitting laser using a GaInNAs mixed crystal semiconductor as an active layer material and a quartz single mode fiber are combined, the 1.3 μm band is made of quartz. Since it corresponds to the zero-dispersion band, the configuration is very suitable for high-speed modulation, and high-speed, large-capacity optical communication and optical transmission can be performed. Further, the surface emitting semiconductor laser device using the GaInNAs mixed crystal semiconductor as an active layer can stably oscillate up to a high temperature even with a change in environmental temperature and the like, and thus has an extremely reliable optical communication system. Can be obtained.

As described above, in the ninth embodiment, the surface-emission semiconductor laser device according to the fifth embodiment, the surface-emission laser array according to the sixth embodiment, or the surface-emission laser according to the seventh embodiment. By using the module, it is possible to provide an optical communication system that enables high-speed and large-capacity optical communication, has high power conversion efficiency, and has high reliability.

Here, the LAN has been described as the optical communication system, but in addition to this, the trunk line system, WAN, M
It can also be used for AN and the like. In addition, the terminal can be used for all information device terminals that exchange information by light.

[0175]

As described above, according to the first to fifth aspects of the invention, the refractive index between the two kinds of semiconductor layers having different refractive indexes is between the two kinds of semiconductor layers. In the semiconductor distributed Bragg reflector having an intermediate layer with a thickness of the intermediate layer in some regions of the semiconductor distributed Bragg reflector is different from the thickness of the intermediate layer in other regions, the reflectance is reduced. It is possible to provide a semiconductor distributed Bragg reflector having a low resistance and a small light absorption loss without causing the above.

According to the sixth and seventh aspects of the invention, since the semiconductor distributed Bragg reflector according to any one of the first to fifth aspects is used, the oscillation light is absorbed. It is possible to provide a highly efficient surface emitting semiconductor laser device that has low loss, low resistance, high output operation, and high efficiency.

Further, according to the invention of claim 8, since it is constituted by the surface emitting semiconductor laser element of claim 6 or 7, the absorption loss of the oscillation light is low, and the resistance is low and high. It is possible to provide a highly efficient surface emitting laser array capable of output operation.

According to the invention described in claim 9, since the surface emitting semiconductor laser device according to claim 6 or 7 or the surface emitting laser array according to claim 8 is used, a high output is obtained. Operable, high power conversion efficiency,
It is possible to provide a surface emitting laser module with low power consumption.

According to the invention of claim 10, the surface emitting semiconductor laser device according to claim 6 or 7,
Alternatively, the surface emitting laser array according to claim 8, or
Since it is an optical interconnection system configured by using the surface emitting laser module according to claim 9, it is possible to provide an optical interconnection system with low power consumption and high power conversion efficiency.

According to the invention described in claim 11, the surface emitting semiconductor laser device according to claim 6 or 7,
Alternatively, the surface emitting laser array according to claim 8, or
Since it is an optical communication system configured by using the surface emitting laser module according to claim 9, it is possible to provide an optical communication system with low power consumption and high power conversion efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a specific example of a semiconductor distributed Bragg reflector according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a linear composition gradient layer.

FIG. 3 is a diagram showing a configuration example of a p-type semiconductor distributed Bragg reflector I of FIG.

4 is a diagram showing a configuration example of a p-type semiconductor distributed Bragg reflector II of FIG.

FIG. 5 shows the resistivity of four pairs of p-type semiconductor distributed Bragg reflectors in the 0.98 μm band with respect to the thickness of the composition gradient layer with the Al composition of the low refractive index layer constituting the Bragg reflector as a parameter. It is the figure shown.

FIG. 6 is a graph showing five pairs of p-type semiconductor distributed Bragg reflectors in the 0.98 μm band, the reflectance being the thickness of the intermediate layer (composition gradient layer) with the Al composition of the low refractive index layer constituting the Bragg reflector as a parameter. FIG.

FIG. 7 is a diagram showing a specific example of a semiconductor distributed Bragg reflector according to a second embodiment of the present invention.

8 is a diagram showing a configuration of a p-type semiconductor distributed Bragg reflector I of FIG.

9 is a diagram showing a configuration of a p-type semiconductor distributed Bragg reflector II of FIG.

FIG. 10 is a diagram showing a specific example of a semiconductor distributed Bragg reflector according to a third embodiment of the present invention.

11 is a region I of the semiconductor distributed Bragg reflector of FIG.
FIG.

FIG. 12 is a region II of the semiconductor distributed Bragg reflector of FIG.
FIG.

FIG. 13 is a diagram showing a specific example of the semiconductor distributed Bragg reflector of the fourth embodiment.

14 is a region I of the semiconductor distributed Bragg reflector of FIG.
FIG.

FIG. 15 is a region II of the semiconductor distributed Bragg reflector of FIG.
FIG.

FIG. 16 is a diagram showing the reflectance with respect to the thickness of a compositionally graded layer, using the Al composition of the low refractive index layer as a parameter, for five pairs of semiconductor distributed Bragg reflectors having a reflection wavelength of 1.3 μm.

FIG. 17 is a diagram showing a specific example of the surface-emitting semiconductor laser device of the fifth embodiment.

FIG. 18 is a diagram showing an example of a surface emitting semiconductor laser element manufactured by performing crystal growth on a p-type semiconductor substrate.

FIG. 19 is a diagram showing a specific example of a surface emitting laser array according to a sixth embodiment.

FIG. 20 is a diagram showing a specific example of the surface emitting laser module according to the seventh embodiment.

FIG. 21 is a diagram showing a parallel optical interconnection system as an example of an eighth embodiment.

FIG. 22 is a diagram showing an optical LAN system as an example of an optical communication system according to a ninth embodiment.

Claims (11)

[Claims] 1. Between two types of semiconductor layers having different refractive indices,
In a semiconductor distributed Bragg reflector having an intermediate layer having a refractive index between the two types of semiconductor layers, the thickness of the intermediate layer in a part of the semiconductor distributed Bragg reflector is different from that of the intermediate layer in another region. A semiconductor distributed Bragg reflector characterized by being different in thickness. 2. The semiconductor distributed Bragg reflector according to claim 1, wherein the difference in the band gap between the two types of semiconductor layers in the region where the thickness of the intermediate layer is large is the difference in the region where the thickness of the intermediate layer is thin. A semiconductor distributed Bragg reflector characterized by being smaller than the difference in the band gap between two semiconductor layers. 3. The semiconductor distributed Bragg reflector according to claim 1, wherein the thickness of the intermediate layer in the semiconductor distributed Bragg reflector is dependent on the electric field intensity of light in the semiconductor distributed Bragg reflector. And a semiconductor distributed Bragg reflector characterized by different doping concentrations. 4. The semiconductor distributed Bragg reflector according to claim 3, wherein the thickness of the intermediate layer is large and the doping concentration of impurities is low in a region where the electric field intensity of light in the semiconductor distributed Bragg reflector is large. On the other hand, in the region where the electric field intensity of light is low, the thickness of the intermediate layer is thin and the doping concentration of impurities is high, and the semiconductor distributed Bragg reflector is characterized. 5. The semiconductor distributed Bragg reflector according to claim 1, wherein the designed distributed wavelength of the semiconductor distributed Bragg reflector is a long wave longer than 1.1 μm. Semiconductor distributed Bragg reflector. 6. A surface emitting semiconductor laser device comprising the semiconductor distributed Bragg reflector according to any one of claims 1 to 5. 7. The surface emitting semiconductor laser device according to claim 6, wherein the group III material of the active layer is any or all of Ga and In, and the group V material of the active layer is As,
A surface emitting semiconductor laser device characterized in that it is any or all of N and Sb. 8. A surface emitting laser array comprising the surface emitting semiconductor laser device according to claim 6. 9. A surface emitting laser module comprising the surface emitting semiconductor laser device according to claim 6 or claim 7 or the surface emitting laser array according to claim 8. 10. A light configured by using the surface emitting semiconductor laser device according to claim 6 or 7, the surface emitting laser array according to claim 8, or the surface emitting laser module according to claim 9. Interconnection system. 11. A surface-emitting semiconductor laser device according to claim 6 or 7, a surface-emitting laser array according to claim 8, or a light configured using the surface-emitting laser module according to claim 9. Communications system.