JPH11220217A - Semiconductor optical device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of an integrated element by providing a masks of an oxide film and a nitride film on the surface of a substrate in the vicinity of many periodicities, adding raw-material gas including chlorine by organic- metal gaseous-phase growing method, and forming the quantum well structure having the different periodicities on the same substrate by one selective growth. SOLUTION: On an n-InP substrate 1 or an n-InP buffer layer 2, a selective- growing SiO2 mask 3 is deposited. An active layer 4, which is constituted of an n-InGaAsP guide layer 7, a barrier layer 8, a well layer 9, a CH3 Cl added well layer 10 and undoped guide layer 11, is selectively grown by an organic- metal gaseous-phase growing method. Then, the selective-growing SiO2 mask 3 is removed, p-InP clad layers 12 and 13 and a p-InGaAs cap layer 14 are sequentially grown. A p-type cap layer 15 and an n-type cap layer 16 are evaporated. Cleavage is performed at a laser part and a beam expanding part, and the element is formed. Thus, the periodicities of the beam expanding part and the laser part can be independently controlled, and the emitting angle can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor laser, an integrated optical device, an optical module, and a method of manufacturing the same for use in optical communication and the like.

[0002]

2. Description of the Related Art Methods for integrating optical elements having different functions on the same substrate include a selective growth method in which a layer structure having a different growth film thickness is formed by changing the mask area at one time, and an etching method after multi-layer growth. And a different layer structure is formed by regrowth. As an example of the former, JP-A No. 1-3
No. 21677, etc., and an example of the latter is the 8th Indium Phosphide and Related Materials 152-1
There are 54 pages in 1996.

[0003] The former selective growth method is a method of increasing the film thickness of a growth region by enlarging the area of a mask. However, the film thickness ratio is limited to 2 to 3 times. It is difficult. Further, although reduction of the number of cycles is effective for an end face region of an integrated optical device including a waveguide and a laser or a high-power laser, it is impossible to control the number of cycles in-plane.

[0004] In the latter case, a layer structure having a different number of periods is possible, but the number of times of growth is increased and the manufacturing process becomes complicated. Further, defects are likely to be generated at the regrowth interface, and the reliability deteriorates, and the composition changes rapidly, so that reflection at the regrowth interface is a problem.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to integrate devices having different functions not only in the well layer thickness but also in the number of periods and the layer structure. The purpose is to realize a wide integration of waveguides, light receiving elements, modulators, and the like. Further, it is an object of the present invention to improve the reliability of such an integrated device and to manufacture the integrated device at a high yield by a simple method. Another object is to control the structure and composition near the end face of a single high-power semiconductor laser to increase the output and improve the reliability.

[0006]

In order to achieve the above object, the present invention integrates growth regions having different numbers of periods and layer structures by a single selective growth method without exposing a regrowth interface, thereby achieving high reliability. And high yield. A mask pattern was used to integrate elements having different periods and layer structures, and the growth rate and the etching rate were spatially controlled according to the area of the mask pattern to realize selective growth at a desired location. Specifically, an etching gas containing chlorine was supplied during normal selective growth, and in-plane control of growth and etching was performed by a mask pattern.

In the case of a single semiconductor laser, the mask pattern area at the end face is reduced from that of the laser section, the growth rate of the end face area is made equal to or lower than the etching rate, and the growth of the well layer at the end face is stopped. Was.

Hereinafter, the selective growth method of the present invention will be described with reference to FIG. FIG. 4 shows the relationship between the growth rate and the mask width during the selective growth, and the relationship between the etching rate and the mask width. While the growth rate increases significantly with increasing mask width, the etching rate increases only slightly. For this reason, for example, in the integration of the laser unit and the waveguide unit,
When the mask width of the laser portion is 200 μm, the mask width of the waveguide portion is 130 μm, and the growth raw material and the etching raw material are supplied at the same time, the growth and etching in the waveguide portion are in an equilibrium state, and the well layer is grown only in the laser portion. Becomes

Further, since the growth rate and the etching rate when no mask is used depend on the growth material and the supply amount of the etching gas, the mask area, the growth material gas, and the supply amount of the etching gas are controlled to control the in-plane. Growth layers having different numbers of periods and stacked structures can be grown at once.

[0010] Based on the above findings, the present inventors have conceived the following process. The basic feature is that, as a method of forming a quantum well structure having a spatially different number of periods on the same substrate, a mask made of an oxide film or a nitride film is provided on the substrate surface in the vicinity of a region having a large number of periods, Metalorganic vapor phase epitaxy 1
There is a step of forming a quantum well structure having a different number of periods on the same substrate by one selective growth and adding a source gas containing chlorine during the selective growth.

This process is particularly effective when applied to the manufacture of a semiconductor optical device, and can also be applied to the manufacture of a semiconductor integrated optical device, that is, a process of integrating the optical device. The area of the mask used in this process may be set so as to correspond to the number of periods of the quantum well structure so that the mask area of the region having a large number of periods is larger than the mask area of the region having a small number of periods. Further, in the process by the metalorganic chemical vapor deposition method, HCl, CH ₃ Cl, and C ₂ H ₅ Cl may be used as a raw material containing chlorine.

Based on the above process knowledge, the present inventors provide the following semiconductor optical device structure. The basic structure is a semiconductor optical device characterized by having quantum well structures having spatially different numbers of periods on the same substrate.

The quantum well structure having a spatially different number of periods will be specifically described in each of the embodiments described later. However, if it is expressed as an example, at least two types of layers (a band gap between each other) constituting the quantum well structure will be described. Are different). Usually, the two types of layers constituting the quantum well structure are called a quantum well layer and a barrier layer having a larger forbidden band width, and a spacer layer having a larger forbidden band width and smaller than the barrier layer is inserted between them. It may be done.

In many quantum well structures composed of a quantum well layer and a barrier layer, when the number of periods is N, one of the layers has N and the other has (N + 1). Each of the layers is configured to have a relationship of being sandwiched between the other layers (at this time, even if one of the layers is a quantum well layer,
It may be a barrier layer). The quantum well structure formed in the above-described semiconductor optical device may be configured such that the thickness of the well layer is continuously reduced in the transition region in which the number of periods changes in the direction in which the number of periods decreases. The region of the quantum well structure having a small number of periods may be provided near the optical waveguide or the end face of the semiconductor optical device.

As described above, the semiconductor optical device provided by the present invention comprises:
These may be integrated to form a semiconductor integrated optical device. Further, the semiconductor integrated optical device may be formed on a same substrate together with a waveguide and a laser, or a waveguide and a photodetector, or a laser, a waveguide and a photodetector. The optical module may be formed to constitute an optical module (for transmitting, receiving, or transmitting and receiving optical signals).

[0016]

(Embodiment 1) FIG. 1 shows an embodiment in which the present invention is applied to a subscriber beam expanding laser.
1A is a sectional view of the device, FIG. 1B is a sectional view of an active layer, and FIG. 1C is a mask for selective growth.

First, the n-InP substrate 1 or n-I
SiO ₂ mask 3 for selective growth on nP buffer layer 2 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ , thickness: 300 nm)
And the active layer 4 (the number of cycles of the laser section: 7, the number of cycles of the beam expanding section: 1) was selectively grown by metal organic chemical vapor deposition. At this time, the selective growth mask 3 includes a beam expanding portion 5 (mask width × length: 50 μm × 200 μm) and a laser portion 6 (mask width × length: 200 μm × 500 μm).
In (m), the mask width is different, and the mask width of the laser unit having a large number of periods is increased.

The active layer 4 is composed of an n-InGaAsP guide layer 7 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ , thickness: 100).
nm, wavelength 1050 nm), barrier layer 8 (thickness: 10 n)
m, wavelength 1100 nm), well layer 9 (thickness of laser part:
6 nm, thickness of beam expanding portion: 2 nm, wavelength 1370 n
m, strain: 0.8%), CH ₃ Cl-added well layer 10 (laser thickness: 6 nm, wavelength: 1370 nm, strain: 0.8)
8%, the etching amount of the barrier layer is 1 nm), and the undoped guide layer 11 (thickness: 50 nm, wavelength: 1050 nm).

Next, the SiO ₂ mask 3 for selective growth is removed, and the p-InP cladding layer 12 (carrier concentration: 3 ×
10 ¹⁷ cm ⁻³ , thickness: 300 nm), p-InP clad layer 13 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ , thickness: 300)
0 nm), a p-InGaAs cap layer 14 (carrier concentration: 2 × 10 ¹⁹ cm ⁻³ , thickness: 300 nm) is sequentially grown, a p-type cap layer 15 and an n-type cap layer 16 are deposited, and a laser section and a beam are formed. Cleavage was performed at the enlarged portion to make a device.

Hereinafter, the effect of this embodiment will be described. In the conventional selective growth method, a well layer for seven periods is also formed in the beam expanding portion, so that light confinement in the beam expanding portion is strong,
The emission angle of the laser was as large as 16 degrees, and the coupling loss with the fiber was large. On the other hand, in this embodiment in which the beam expanding portion is set to one cycle, the emission angle of the laser can be reduced to 9 degrees,
The coupling loss with the fiber was improved by 40%.

Further, in the conventional method, it is necessary to reduce the number of periods in order to narrow the emission angle of the laser, but in this case, the laser characteristics are rapidly deteriorated. For example, if the number of cycles is 4
, The output angle becomes 13 degrees, but the high temperature (8
(5 ° C.) increases by about 40%. On the other hand, in this embodiment, since the number of periods of the beam expanding section and the laser section can be controlled independently, the emission angle can be reduced without impairing the laser characteristics.

In the case of using another conventional method of regrowth, there is a problem in reliability because the active layer is removed by etching and regrown. Also, the yield has been poor due to the increase in the number of times of growth. On the other hand, in this embodiment, since the active layer is not etched and regrown, the life of the device can be extended by 50% and the yield can be increased by 20%. In this embodiment, the reflection at the regrowth interface is also shown in FIG.
As shown in (b), since the film thickness was gradually reduced, no reflection occurred.

In the present embodiment, the number of periods of the beam expanding section is set to 2. However, other numbers of periods can be used. For example, the output angle is set to 10 degrees for 2 and 8 for 0. It could be reduced to the degree. Further, the etching amount of the beam expanding portion at the time of adding CH ₃ Cl is set to 1 nm. If the etching amount is too large (for example, several hundred nm or more), the surface morphology is deteriorated. If it is balanced), other values may be used.

(Embodiment 2) FIG. 2 is a sectional view of a device and a mask diagram of an oxide film in an embodiment in which the present invention is applied to a high-power semiconductor laser. First, n-GaAs is formed by metal organic chemical vapor deposition.
n-GaAs buffer layer 18 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ , thickness: 300 nm) on s substrate 17, n-In
GaP cladding layer 19 (carrier concentration: 1 × 10 ¹⁸ c
After growth of m ⁻³ , thickness: 2000 nm, lattice matching with GaAs), the selective growth SiO ₂ oxide film 20 (resonator length: 400 μm, active layer region length 21: 350 μm) shown in FIG.
m, end surface area length 22: 25 μm, mask width × length:
50 × 350 μm) is deposited, and the n-InGaAsP guide layer 23 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ , thickness: 50)
nm, lattice matching to GaAs, wavelength: 800 nm), Ga
As barrier layer 23 (thickness: 10 nm), InGaAs well layer 25 doped with CH ₃ Cl (laser thickness: 6 nm, wavelength: 980 nm, distortion: 1.0%, end face etching amount: 1)
nm, number of cycles of laser section: 2, number of cycles of end face region:
0), InGaAsP guide layer 26 (thickness: 50 nm,
After growing lattice matching on GaAs (wavelength: 800 nm), the selection mask is removed by etching, and p-InGaP is removed.
Clad layer 27 (carrier concentration: 8 × 10 ¹⁷ cm ⁻³ , thickness: 2000 nm, lattice-matched to GaAs), p-GaAs
s28 (carrier concentration: 1 × 10 ¹⁹ cm ⁻³ , thickness: 200)
nm), the p-side electrode 29 and the n-side electrode 30 are sequentially grown.
A device was formed by vapor deposition and cleavage.

Hereinafter, the effects of the present invention will be described. In the conventional technique for making the end face transparent by impurity diffusion, there have been problems of generation of defects due to impurities and light absorption in the InGaAs well layer. On the other hand, in the present invention, there is no growth of the InGaAs layer.
Since there is no diffusion etc., the maximum light output can be increased by about 40%,
Reliability can be extended by 30%. Although a mask is not provided near the end face in the present invention, a mask having a small area may be provided as long as the growth rate does not exceed the etching rate.

(Embodiment 3) FIGS. 3A and 3B are a conceptual diagram when the present invention is applied to a transmitting / receiving optical module and an example of a cross-sectional view between a laser and a waveguide. First, after stacking up to the upper guide layer 11 by the same manufacturing method as in Example 1,
The oxide film is removed, and the p-InP12, 1
3, a p-InGaAs cap layer 14 was formed. The mask area at this time was: light receiving section> laser section> waveguide section, and the emission wavelength of the light receiving section was maximized.

The well layer has a composition of InGaAs layer 30 (wavelength 1670) in order to lengthen the composition wavelength of the light receiving portion.
nm, lattice matching with InP), and the emission wavelength of the laser portion was set to 1550 or 1300 nm. Laser part,
The number of periods of the light receiving unit is 6, the number of periods of the waveguide unit is 0 in order to eliminate loss due to the well layer, and the lower and upper guide layers 7,
11 only. Next, the p-InP and p-In
Upper guide layer 11 by selective etching of only GaAs
Etching, mask the laser and light receiving parts,
The e-doped InP or undoped InP layer 31 was selectively grown, and the electrodes 15 and 16 were selectively deposited only on the laser portion and only on the light receiving portion, thereby achieving an element.

Conventionally, a waveguide and a laser, a waveguide and a light receiving section,
In addition, since the respective elements of the waveguide, the laser, and the light receiving unit are coupled by using a lens, it is difficult to reduce the size, and it takes time for positioning. On the other hand, according to the present invention, the size can be reduced to about 1/5 by the collective selective growth, and the alignment time can be reduced to about 1/3.

In this embodiment, the composition of the well layer is InG
aAs, and the wavelength of the light receiving portion was set to 1670 nm. However, if the wavelength is longer than the laser, light can be received.
At 0 nm, use InGaAsP for 1350 nm or more,
Preferably, if it is 1400 nm or more, InGaAsP
It may be a well layer. In this embodiment, the number of cycles is set to 6 for the laser section and the light receiving section. Further, in the manufacturing method, the Fe or undoped InP layer 31 was grown after etching, but the p-InP, InGaAs layers 12, 13, 1 were formed by an oxide film.
Only 4 may be selectively grown.

In the above Examples 1, 2 and 3, CH ₃ Cl was used as the source gas containing chlorine, but other sources containing chlorine include C ₂ H ₅ Cl, HCl, AsCl ₄ , PCl _{4 and the} like. Yes, all can be used, but there is also a raw material for producing an organic metal and an intermediate product. When growing GaAs, CH ₃ Cl, C
₂ H ₅ Cl, HCl, etc. are desirable at the time of InP growth C
H ₃ Cl, C ₂ H ₅ Cl and the like are desirable. Further, although SiO ₂ is used as the oxide film for the selective growth mask of this embodiment, a nitride film SiN may be used.

[0031]

According to the present invention, it is possible to reduce the number of wells in the beam expanding portion and the end face region while preserving the number of wells in the laser portion. A semiconductor can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an element (a) of Example 1 of the present invention,
(B) Sectional view of the active layer, (c) plan view of the mask used.

FIG. 2 is a sectional view of an element (a) according to a second embodiment of the present invention,
(B) A plan view of the mask used.

3A is a conceptual diagram of an optical module for transmission and reception according to a third embodiment of the present invention, and FIG.

FIG. 4 is a graph showing a relationship between a mask width, a growth rate, and an etching rate according to the principle of the present invention.

[Explanation of symbols]

1 ... n-InP substrate, 2 ... n-InP buffer layer, 3 ...
Oxide film for selective growth, 4 ... active layer, 5 ... length of waveguide section,
6: length of laser portion, 7: n-side guide layer, 8: barrier layer,
9 Quantum well layer, 10 Quantum well layer when Cl-based material is added, 11 Undoped guide layer, 12 p-InP layer,
13 ... p-InP layer, 14 ... p-InGaAs cap layer, 1
5 ... p-side electrode, 16 ... n-side electrode, 17 ... n-GaAs substrate, 18 ... n-GaAs buffer layer, 19 ... n-InG
aP cladding layer, 20: oxide film for selective growth, 21: length of end face region, 22: length of laser portion, 23: lower guide layer, 24: barrier layer, 25: quantum well layer, 26: upper guide Layer, 27 ... p-InGaP cladding layer, 28 ... p-G
aAs cap layer, 29 ... p-side electrode, 30 ... n-side electrode,
31 ... Fe or undoped InP layer.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Masahiro Aoki 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Central Research Laboratory

Claims (7)

[Claims] 1. A semiconductor optical device having quantum well structures having spatially different numbers of periods on the same substrate. 2. A method of forming a quantum well structure according to claim 1, wherein a mask made of an oxide film or a nitride film is provided on a substrate surface in the vicinity of a region having a large number of periods, and wherein the mask is formed by metal organic chemical vapor deposition. A method for manufacturing a semiconductor optical device, comprising: forming quantum well structures having different numbers of periods on the same substrate in a single selective growth; and adding a source gas containing chlorine during the selective growth. 3. The method of manufacturing a semiconductor optical device according to claim 2, wherein a mask area of a region having a large number of periods is larger than a mask area of a region having a small number of periods. 4. A semiconductor optical device according to claim 1, wherein in a transition region in which the number of periods of the semiconductor optical device changes, the thickness of the well layer continuously decreases as the number of periods decreases. 5. The semiconductor optical device according to claim 4, wherein
A semiconductor optical device wherein a region having a small number of periods is near an optical waveguide or an end face. 6. A raw material containing chlorine in the metalorganic vapor phase epitaxy according to claim 2, wherein HCl, CH ₃ Cl, C ₂
The method of manufacturing a semiconductor optical device, which comprises using at least one party of H ₅ Cl. 7. The semiconductor optical device according to claim 5, wherein
A semiconductor integrated optical device, wherein a waveguide and a laser, a waveguide and a light receiver, or a laser, a waveguide, and a light receiver are formed on the same substrate.