JP2003283053A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To offer a semiconductor laser device with increased design freedom, better workability, and higher reliability. <P>SOLUTION: On an n-GaAs substrate 11, an n-Al<SB>0.52</SB>Ga<SB>0.48</SB>As lower cladding layer 12, an n-InGaAsP or i-InGaAsP lower light guide layer 13, an i-InGaAs compressively-strained quantum well active layer 14, a p-InGaAsP or i-InGaAsP upper light guide layer 15, a p-In<SB>0.49</SB>Ga<SB>0.51</SB>P first upper cladding layer 16, a p-InGaAsP etching stop layer 17 and an n-InGaP current blocking layer 18 (from which regions corresponding to stripe regions are removed), a p-In<SB>0.49</SB>Ga<SB>0.51</SB>P second upper cladding layer 19, and a p-GaAs contact layer 20, are laminated in the described order. The lower cladding layer and the upper cladding layer differ in composition. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor laser device.

[0002]

2. Description of the Related Art In recent years, semiconductor laser devices are small and inexpensive.
It has attracted attention in various fields due to its advantages such as high efficiency and low power consumption, and is widely applied as a light source. Most of the semiconductor laser devices currently commercialized are G
After crystal growth of a basic layer including a clad layer, an active layer, a current confinement, a contact layer, etc. on an aAs or InGaP substrate, mode control, current confinement, etc. are performed by a semiconductor process including a lithography process and a processing process. The structure of is built in.

However, the semiconductor process is highly dependent on the material, and the shape may change depending on the material and the crystal orientation particularly in the processing by wet etching, and it may be difficult to produce a desired shape depending on the material used. As an example, a case of processing AlGaAs will be described. For example, in a 0.8 μm band semiconductor laser device,
On a -GaAs substrate, an n-AlGaAs clad layer, an active layer, a p-AlGaAs clad layer and a p-GaAs
After growing the contact layer, p-AlG is formed using a mask.
Some have a ridge formed by etching halfway through the aAs clad. The width of the ridge is a very important parameter for controlling the transverse mode of the semiconductor laser device,
It must be formed with high precision.

[0004]

[Problems to be Solved by the Invention] However, AlGaA
When etching the s-clad layer, there is a problem that it is difficult to control the ridge shape because the so-called side etching in which the lower part of the mask is laterally etched is large. Therefore, in order to realize this structure, it is necessary to control the mask width, the etching time, the temperature of the solution, and the like with high accuracy. Further, even if such a measure is taken, the in-plane variation in the actually manufactured ridge shape is large, so that the yield is low and the cost rises.

In view of the above circumstances, it is an object of the present invention to provide a semiconductor laser device having a high degree of freedom in crystal growth and a semiconductor process, a low cost and a high reliability.

[0006]

A semiconductor laser device of the present invention is a semiconductor laser device having an active layer sandwiched between a pair of n-type and p-type clad layers. It is characterized in that at least a part is made of different semiconductors, and the refractive indices are almost the same.

At least a part of one of the pair of clad layers is made of AlGaAs, and at least a part of the other is made of InGaAs.
It is preferably made of GaP.

At least a part of one is AlGaA.
s and at least a part of the other may be AlGaInP. Further, at least a part of one is made of InP and at least a part of the other is made of AlG.
It may be made of aInAs.

[0009]

According to the semiconductor laser device of the present invention, since the pair of cladding layers are made of semiconductors at least partially different from each other and have substantially the same refractive index,
An optical design equivalent to the case of using the same material for a pair of clad layers is possible, and when the clad layers must be processed for current constriction or mode control, the material that is easy to process is the side to be processed. Since it can be used for the clad layer, the degree of freedom in design and the processing accuracy are increased, and high reliability can be obtained.

Further, since it is possible to select the optimum material in consideration of the fact that the crystallinity of the adjacent layer and the clad layer changes depending on the composition of the clad layer, the crystallinity can be enhanced.

Further, since the manufacturing process can be simplified due to the ease of processing, the cost can be reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor laser device according to the first embodiment of the present invention. As shown in FIG. 1, this semiconductor laser device has an n-GaAs substrate 11 with n
-Al _0.52 Ga _0.48 As lower clad layer 12, i-InG
aAsP lower optical guide layer 13, i-InGaAs compressive strained quantum well active layer 14, i-InGaAsP upper optical guide layer 1
5, p-In _0.49 Ga _0.51 P upper first cladding layer 16, p-InGa from which the region corresponding to the stripe region has been removed
AsP etching stop layer 17 and n-AlGaIn
P current blocking layer 18, p-In _0.49 formed thereon
Ga _0.51 P upper second cladding layer 19, p-GaAs contact layer 20, insulating film 22 formed in a region other than the region corresponding to the stripe region, p-side electrode 23, and n-side electrode formed on the back surface of substrate 11. 24, and the end reflection films 25 and 26
And grooves 21 for reducing parasitic capacitance on both sides of the stripe.

The light emitting region sandwiched between the two cladding layers is
This is a SCH (Separate Confinement Heterostructure) structure including the optical guide layers 13 and 15 and the quantum well active layer 14. The clad layer preferably has a composition that lattice-matches GaAs.

Now, a method of designing and manufacturing the semiconductor laser device according to the first embodiment will be described.
Wet etching is used in both the step of etching the n-AlGaInP current blocking layer for forming the optical waveguide and the step of forming the two trenches for reducing the parasitic capacitance. These forming methods are
It is utilized that, when GaP and AlGaInP are etched using hydrochloric acid, the lateral wraparound etching is reduced due to the influence of anisotropy on the plane orientation. This is a unique phenomenon due to the combination of the InGaP-based material and the etching with hydrochloric acid, and FIG. 2 shows the difference between the two. FIG. 2 is a cross-sectional view of a part of the semiconductor laser device, showing a process of etching the cladding layer 33 using the mask 35. This semiconductor laser device has a structure in which an active layer 32 and an upper clad layer 33 are laminated on a lower clad layer 31, and an etching stopper layer 34 is provided between the upper clad layer 33. 2 (a) shows the case where the upper cladding layer 33 is AlGaAs, and FIG.
Indicates the case where the upper clad layer 33 is InGaP. AlG
In the case of aAs, the side etching amount is large as shown in FIG. 2 (a), but in the case of InGaP, there is almost no side etching as shown in FIG. 2 (b). As described above, when AlGaAs is used for the cladding layer or the current blocking layer on the side to be processed, it is difficult to control the groove width because the side etching is large. Therefore, as a semiconductor material for the cladding layer on the side of processing, In
By using P, InGaP, or AlGaInP, a process with good reproducibility becomes possible and etching can be performed with high accuracy.

On the other hand, in terms of manufacturing, the first cladding layer of the pair of cladding layers, that is, the lower cladding layer on the substrate side is preferably AlGaAs rather than InGaP. I
nGaP is a material that is thermally unstable as compared to AlGaAs because the group V elements are all formed of only phosphorus, and there is a problem that the crystallinity is likely to deteriorate. In particular, in crystal growth by MOCVD, I
When growing an arsenic compound such as nGaAsP, InGa
After the growth of P, phosphorus on the InGaP surface is replaced with arsenic,
The crystal quality of the InGaAsP that continues to grow deteriorates. On the other hand, AlGaAs is thermally stable because it contains arsenic as a group V element, and subsequently, InGa
The growth of AsP has the advantage that high quality crystals are easily obtained.

If InGaP is used for the upper clad layer, it is more natural to use InGaP for the lower clad layer in designing the semiconductor laser device, but for the above reason, the lower clad layer is advantageous in crystallinity. AlGaAs
However, by using InGaP, which is advantageous in terms of workability, for the upper clad layer, it is possible to provide a semiconductor laser device superior in characteristics and cost.

Further, by making AlGaAs and InGaP used for the upper clad layer and the lower clad layer substantially equal in refractive index, it is possible to optically design the same as when a clad made of the same semiconductor is used.

In the structure of the semiconductor laser device according to the above embodiment, the p-InGaAsP etching stop layer 17 may partially remain.

Further, as shown in FIG. 3, p-In _0.49 G
An etching stopper layer 27 made of, for example, InGaAsP may be provided in the middle of the a _0.51 P upper first cladding layer 16 in the stacking direction. As a result, the upper clad layer can be brought closer to the active layer and the step of the equivalent refractive index can be made large, so that higher quality laser light can be obtained.

Furthermore, as shown in FIG. 4, p-In
The GaAsP etching stop layer 17 may not be provided. Therefore, a part of the p-In _0.49 Ga _0.51 P upper first cladding layer 16 may be etched. In such a structure, since the i-InGaAsP light guide layer 15 is formed thickly, the light density is reduced as a result, and the light output reaching the end face destruction can be increased, so that the life of the device can be lengthened.

In the above embodiment, the case where the lower clad layer 12 is AlGaAs and the upper first clad layer 16 and the upper second clad layer 19 are both InGaP has been described. In _0.49 Ga _0.51 P
Instead of AlGaAs, specifically p-Al _0.52 Ga
_It may be _0.48 As.

Next, a semiconductor laser device having a ridge structure according to the second embodiment of the present invention will be described. A sectional view of the semiconductor laser device is shown in FIG.

The semiconductor laser device according to the present embodiment is
As shown in FIG. 5, n-Al is formed on the n-GaAs substrate 41.
_0.52 Ga _0.48 As lower clad layer 42, i-InGaAs
P lower optical guide layer 43, i-InGaAs compressive strain quantum well active layer 44, i-InGaAsP upper optical guide layer 45, p-
In _0.49 Ga _0.51 P upper cladding layer 46, p-GaAs contact layer 47, insulating film 48, p-side electrode 49 and n-side electrode 50
And has a ridge structure formed by etching a part of the p-In _0.49 Ga _0.51 P upper cladding layer 46.

In the semiconductor laser device according to the present embodiment
Indicates that the upper clad layer 46 is In_0.49Ga _0.51Consists of P,
Since the upper light guide layer 45 is made of InGaAsP,
The upper light guide layer 45 automatically etches the cladding layer 46.
It is possible to stop at the surface of the
As for InGaP etching, side etching is extremely
Since it is very small, it is possible to obtain a highly accurate ridge structure.
It is possible to obtain a semiconductor laser device with high reliability.
It

Further, as shown in FIG. 6, p-In _0.49 G
a _0.51 P InGa is formed in the middle of the stacking direction of the upper clad layer 46.
An etching stop layer 51 made of AsP may be provided, which makes it possible to obtain a large equivalent refractive index step.
High quality laser light can be obtained.

In the semiconductor laser device according to the first and second embodiments, one cladding layer is made of AlG.
It has been described that it is a As and the other cladding layer is only InGaP, or InGaP and AlGaAs, but at least a part of one is AlGaInP.
And at least a part of the other may be made of AlGaAs. Also, at least a part of one is A
lGaInAs and at least part of the other is In
It may be made of P. That is, when one clad layer is composed of a plurality of clad layers, one of the clad layers may be a semiconductor material different from that of the other clad layer.
Further, when the clad layer on the side to be processed is divided into a plurality of pieces, it is desirable that the clad layer in the region where the groove width is desired to be formed with high control is made to have a composition excellent in workability.

[Brief description of drawings]

FIG. 1 is a perspective view showing a semiconductor laser device according to a first embodiment of the present invention.

[Fig. 2] When the cladding layer on the side to be processed is AlGaAs
(a) and InGaP (b) cross-sectional view showing the etching state

FIG. 3 is a sectional view showing another form of the semiconductor laser device according to the first embodiment.

FIG. 4 is a cross-sectional view showing another form of the semiconductor laser device according to the first embodiment.

FIG. 5 is a sectional view showing a semiconductor laser device according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing another form of the semiconductor laser device according to the second embodiment.

[Explanation of symbols]

11 n-GaAs substrate 12 n-Al _0.52 Ga _0.48 As lower cladding layer 13 n or i-InGaAsP lower optical guide layer 14 i-InGaAs compression strain quantum well active layer 14 p or i-InGaAsP upper optical guide layer 15 p-In _0.49 Ga _0.51 P upper first cladding layer 17 p-InGaAsP etching stop layer 18 n-AlGaInP current blocking layer 19 p-In _0.49 Ga _0.51 P upper second cladding layer 20 p-GaAs contact layer 21 groove 22 insulating film 23 p side Electrode 24 n-side electrode 25,26 Reflective film

Claims (4)

[Claims] 1. A semiconductor laser device having an active layer sandwiched between a pair of n-type and p-type clad layers, wherein the pair of clad layers are made of semiconductors at least partially different from each other and have a refractive index. A semiconductor laser device having a substantially equal rate. 2. The semiconductor laser device according to claim 1, wherein at least a part of one of the pair of cladding layers is made of AlGaAs, and at least a part of the other is made of InGaP. 3. The semiconductor laser device according to claim 1, wherein at least a part of one of the pair of cladding layers is made of AlGaAs, and at least a part of the other is made of AlGaInP. 4. At least a part of one of the pair of cladding layers is made of InP, and at least a part of the other is Al.
2. The semiconductor laser device according to claim 1, which is made of GaInAs.