JPH08250811A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE: To enable a semiconductor light emitting device to oscillate in a single transverse mode when the device operates at a high output level by forming a p-type InGaAsP light guide layer having a refractive index higher than that of an InGaP clad layer and lower than that of GaAs. CONSTITUTION: A light emitting area A is formed by successively forming an n-type InGaP clad layer 2, an active layer 3, a p-type InGaP clad layer 4, a p-type InGaAsP light guide layer 5, p-type InGaP clad layers 4 and 7, and a p-type GaAs contact layer 8 on an n-type GaAs substrate 1. Current block sections formed as buried areas B are formed by successively forming the clad layer 2, an active layer 3, a clad layer 4, an n-type InGaP current blocking layer 6, a clad layer 7, and a contact layer 8 on the substrate 1. The refractive index of the guide layer 5 is made higher than that of the clad layer 4 and lower than that of GaAs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device such as a semiconductor laser, and more particularly to a semiconductor light emitting device having a single transverse mode.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor light emitting device having an oscillation wavelength in a band of 0.6 to 1.1 μm, for example, a document "High power COD
-free operation of 0.98 μm InGaAs / GaA
s / InGaP lasers with non-injection regions n
ear the facets ”, M. Sagawaet.al., Electronics Lette
The one shown in rs Vol.30 No.17 pp141 0-1411 (1994) is known.

In this semiconductor light emitting device, as shown in the schematic front view of FIG. 6, the light emitting region A is n on the n-GaAs substrate 1.
-InGaP clad layer 2, active layer 3, p-InGaP
Cladding layer 4, p-GaAs optical guide layer 14, p-InG
The aP cladding layers 4 and 7 and the contact layer 8 are laminated in this order, and the current blocking portion which is the buried region B is formed on the n-GaAs substrate 1 by the n-InGaP cladding layer 2.
Active layer 3, p-InGaP clad layer 4, n-InGa
The P current blocking layer 6, the p-InGaP cladding layer 7, and the contact layer 8 are laminated in this order. In the figure, 9 is a p-electrode and 10 is an n-electrode. Further, the waveguiding direction is a direction perpendicular to the paper surface.

In this type of semiconductor light emitting device, in order to meet the demand for higher functionality of information / image processing, for example,
It is desired to improve the beam quality. Then, as one measure for improving the beam quality in this way, a single transverse mode is considered. Conventionally, in order to achieve this single transverse mode, a GaAs optical guide layer having a larger refractive index than InGaP is provided in the light emitting region A as described above to control the transverse mode.

[0005]

However, in the case of achieving the single transverse mode as described above, it is necessary to control the thickness of the GaAs optical guide layer within a very thin range. In other words, in order to achieve high output, it is necessary to make the width of the light emitting region A as wide as possible. For that purpose, the effective refractive index difference ΔNef between the active layer portions in the light emitting region A and the embedding region B is set to a considerably high accuracy. Must be controlled by.

FIG. 7 shows the calculation result of the relationship between the thickness of the GaAs optical guide layer and the effective refractive index difference ΔNef. In this case, the effective refractive index difference ΔNef is expressed as, for example,
If you try to control in the range of 0.006 to 0.007,
The thickness of the light guide layer must be controlled within the range of 18-21 nm. However, at the actual manufacturing level, it is extremely difficult to control the thickness of the light guide layer within this range with good reproducibility. Therefore, a semiconductor light emitting device that oscillates in a single transverse mode during high-power operation has a low yield in manufacturing, which leads to an increase in manufacturing cost.

The above conventional device also has a problem that it is difficult to obtain good crystallinity when growing the GaAs optical guide layer after growing the InGaP cladding layer. That is, in InGaP and GaAs, the group V atom needs to be completely switched from P (phosphorus) to As (arsenic) at the interface between them, but it is very difficult to realize it with the current crystal growth apparatus. Has become.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a semiconductor light emitting device that can oscillate in a single transverse mode even during high-power operation and is easy to manufacture.

[0009]

In a first semiconductor light emitting device according to the present invention, a light emitting region has a first cladding layer, an active layer, a second cladding layer, a second optical guide layer for transverse mode control, and a second light guiding layer.
The clad layer and the contact layer are laminated in this order, and the current blocking portion that is the buried region is the first clad layer,
An active layer, a second clad layer, a first current blocking layer, a second clad layer, and a contact layer are laminated in this order (however, the first and second indicate one and the other of n-type and p-type, respectively). In the buried structure type semiconductor light emitting device in which the second cladding layer is an InGaP cladding layer, the second optical guide layer is made of InGaAsP having a refractive index larger than that of the InGaP cladding layer and smaller than GaAs. It is characterized by that.

A second semiconductor light emitting device according to the present invention is a buried structure type semiconductor in which the light emitting region and the current blocking portion have the same basic layer structure as described above, and the second cladding layer is an InGaAsP cladding layer. In the light emitting device, the second light guide layer has a refractive index larger than that of the InGaAsP cladding layer and smaller than that of GaAs.
It is characterized by being formed from aAsP.

[0011]

In the conventional device, it is necessary to control the thickness of the light guide layer within a very thin range because the InGaP forming the second cladding layer and the light guide layer are formed. This is because the difference in the refractive index between GaAs and GaAs is too large.

Therefore, in the first semiconductor light emitting device of the present invention, the refractive index of the second optical guide layer is smaller than that of GaAs (the refractive index is larger than that of the InGaP second cladding layer in order to guide light). ) When formed from InGaAsP, the allowable range of the thickness of this second optical guide layer becomes large, and even when the currently provided epitaxial growth apparatus (for example, metal organic vapor phase crystal growth apparatus: MOVPE) is used, at the time of high output operation. A semiconductor light emitting device that oscillates in a single transverse mode can be manufactured with a high yield.

The second semiconductor light emitting device of the present invention is different from the first semiconductor light emitting device in that the second cladding layer is made of InGaAsP, but in this case as well, the second optical guide layer has a refractive index. Is smaller than GaAs (which has a higher refractive index than the second cladding layer of InGaAsP to guide light), the allowable range of the thickness of the second optical guide layer becomes large as described above. A semiconductor light-emitting device that oscillates in a single transverse mode during high-power operation can be manufactured with high yield.

Further, since the crystal growth from the second cladding layer to the second optical guide layer in the first semiconductor light emitting device of the present invention is crystal growth from InGaP to InGaAsP, the crystallinity of the present device is also conventional. It will be better than that.

On the other hand, the crystal growth from the second cladding layer to the second optical guide layer in the second semiconductor light emitting device of the present invention is the crystal growth from InGaAsP to InGaAsP. It will be better than that.

Then, the second optical guide layer is formed of InGaAsP.
The absorption loss of light becomes smaller than that of the case where GaAs is used, whereby the intracavity loss can be suppressed small and the differential quantum efficiency can be increased.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a schematic front view of a semiconductor laser according to the first embodiment of the present invention. A light emitting region A of this semiconductor laser includes an n-InGaP cladding layer 2, an active layer 3, and p-InGa on an n-GaAs substrate 1.
P-clad layer 4, p-InGaA with wavelength composition of 800 nm
sP light guide layer 5, p-InGaP cladding layers 4, 7,
And the p-GaAs contact layer 8 are stacked in this order, and the current blocking portion which is the buried region B is n-Ga.
On the As substrate 1, the n-InGaP clad layer 2, the active layer 3, the p-InGaP clad layer 4, the n-InGaP current blocking layer 6, the p-InGaP clad layer 7, and the p-layer.
The -GaAs contact layer 8 is laminated in this order.
In the figure, 9 is a p-electrode and 10 is an n-electrode. Further, the waveguiding direction is a direction perpendicular to the paper surface.

Here, the p-InGaP clad layer 4 is formed.
Has a refractive index of 3.23, and the p-InGaAsP optical guide layer 5 has a refractive index of 3.34, which is larger than that of the cladding layer 4 and smaller than 3.62 of GaAs.

FIG. 2 shows the relationship between the thickness of the p-InGaAsP optical guide layer 5 and the effective refractive index difference ΔNef between the active layer portions in the light emitting region A and the buried region B in the semiconductor laser of the first embodiment. The calculation result is shown. In this case, the above-mentioned effective refractive index difference ΔNef is 0.00
If the thickness is set to 6 to 0.007, the thickness of the light guide layer 5 may be controlled to the range of 43 to 51 nm. This optical guide layer thickness is a value that can be sufficiently controlled by the epitaxial growth apparatus currently provided.

FIG. 3 shows the results of actual measurement of the drive current-optical output characteristics of the semiconductor laser of the first embodiment. As shown in the figure, this semiconductor laser shows a single transverse mode characteristic without a kink even under a high output of 160 mW.

As in the device of the first embodiment, by providing an InGaAsP optical guide layer in the InGaP clad layer, the optical guide layer is formed into InGaP.
It can be utilized as an etching stop layer when selectively etching only the cladding layer. Therefore, it is possible to manufacture the semiconductor light emitting device with good controllability by applying the selective etching in the liquid phase.

Next, a second embodiment of the present invention will be described. FIG. 4 shows a semiconductor laser according to the second embodiment of the present invention. Light emitting area A of this semiconductor laser
Is an n-InGaAsP cladding layer 11, an active layer 3, and a p-InGa layer having a wavelength composition of 700 nm on an n-GaAs substrate 1.
AsP clad layer 12, p-InG with wavelength composition of 780 nm
aAsP optical guide layer 15, p-InGaAsP clad layer
12, 13 and the p-GaAs contact layer 8 are laminated in this order, and the current blocking portion which is the buried region B is
n-InGaAsP clad layer on n-GaAs substrate 1
11, active layer 3, p-InGaAsP clad layer 12, n-
The InGaP current blocking layer 6, the p-InGaAsP cladding layer 13, and the p-GaAs contact layer 8 are laminated in this order.

The p-InGaAsP cladding layer 12 has a refractive index of 3.24, and the p-InGaAsP optical guide layer 15 has a refractive index of 3.24.
Has a refractive index higher than that of the cladding layer 12 and has a GaA
It is 3.33, which is smaller than the refractive index of s of 3.62.

FIG. 5 shows the result of calculation of the relationship between the thickness of the p-InGaAsP optical guide layer 15 and the effective refractive index difference ΔNef in the semiconductor laser of the second embodiment. In this case, if the effective refractive index difference ΔNef is set to 0.006 to 0.007 as described above, the thickness of the optical guide layer 15 may be controlled to be 54 to 63 nm. This optical guide layer thickness is also a value that can be sufficiently controlled by the epitaxial growth apparatus currently provided.

[Brief description of drawings]

FIG. 1 is a schematic front view of an apparatus according to a first embodiment of the present invention.

FIG. 2 shows the thickness of the light guide layer in the device of the first embodiment,
A graph showing the relationship between the effective refractive index difference ΔNef in the active layer portion in the light emitting region A and the buried region B.

FIG. 3 is a graph showing drive current vs. optical output characteristics of the first embodiment device.

FIG. 4 is a schematic front view of a second embodiment device of the present invention.

FIG. 5 shows the thickness of the light guide layer in the device of the second embodiment,
A graph showing the relationship between the effective refractive index difference ΔNef in the active layer portion in the light emitting region A and the buried region B.

FIG. 6 is a schematic front view of a conventional semiconductor laser.

FIG. 7 is a graph showing the relationship between the thickness of the light guide layer in the conventional semiconductor laser and the effective refractive index difference ΔNef between the active layer portions in the light emitting region A and the buried region B.

[Explanation of symbols]

1 n-GaAs substrate 2 n-InGaP cladding layer 3 Active layer 4 p-InGaP cladding layer 5 p-InGaAsP optical guide layer (wavelength composition 800 n
m) 6 n-InGaP current blocking layer 7 p-InGaP clad layer 8 p-GaAs contact layer 9 p electrode 10 n electrode 11 n-InGaAsP clad layer 12 p-InGaAsP clad layer 13 p-InGaAsP clad layer 15 p-InGaAsP light Guide layer (wavelength composition 780 n
m) 20 p-GaAs optical guide layer

Claims (2)

[Claims] 1. A light emitting region having a first cladding layer, an active layer, a second cladding layer, a second optical guide layer for controlling a transverse mode, and a second cladding layer.
The clad layer and the contact layer are laminated in this order, and the current blocking portion, which is the buried region, includes the first clad layer, the active layer, the second clad layer, the first current block layer, the second clad layer, and the contact layer in this order. In the embedded structure type semiconductor light emitting device in which the second cladding layer is an InGaP cladding layer, the second and the second cladding layers are laminated (however, the first and second represent one and the other of n-type and p-type, respectively). The optical guide layer has a refractive index larger than that of the InGaP cladding layer but smaller than that of GaAs.
A semiconductor light-emitting device characterized by being formed from sP. 2. A light emitting region having a first clad layer, an active layer, a second clad layer, a second optical guide layer for controlling a transverse mode, and a second clad layer.
The clad layer and the contact layer are laminated in this order, and the current blocking portion, which is the buried region, includes the first clad layer, the active layer, the second clad layer, the first current block layer, the second clad layer, and the contact layer in this order. In the embedded structure type semiconductor light emitting device, wherein the second clad layer is an InGaAsP clad layer, wherein the second clad layer is an InGaAsP clad layer. The optical guide layer has a refractive index larger than that of the InGaAsP clad layer and smaller than that of GaAs.
A semiconductor light-emitting device characterized by being formed from aAsP.