JPH03145172A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable the control of a lateral mode without depending on a loss wave guide by a method wherein a part of a clad layer formed on one side of an active layer whose other side faces toward a substrate is made to change in an actual refractive index in the lateral direction by providing a layer of high refractive index layer. CONSTITUTION:A first InGaAlP clad layer 11, an InGaP active layer 12, and a second InGaAlP clad layer 13 are successively laminated on a GaAs substrate 10 to form a double hereto-junction structure. An Int (Ga1-wAlw)1-tP(0.48<=t<=0.52) high refractive index layer 14 is formed on the second InGaAlP clad layer 13, and the high refractive index layer 14 is partially etched into a stripe shape. A Ga1-uAluAs(0.48w+0.23<u<=0.75) low refractive index layer 16 as a current constriction layer is formed on both the sides of the layer 14. A GaAs contact layer 17 is formed on the high refractive index layer 14 and the low refractive index layer 16. By the formation of these refractive index layers, an actual refractive index difference large enough for the control of a lateral mode can be realized, so that a semiconductor laser of this design is able to oscillate stably in a basic lateral mode.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor laser device used as a light source for optical information processing, optical measurement, etc., and a method for manufacturing the same.

(Conventional technology) In recent years, 0. InGaAJP red lasers with an oscillation wavelength in the Bμm band have been commercialized and are expected to find wide application as light sources for high-density optical disk devices, laser beam printers, barcode leagues, optical measuring instruments, etc. Particularly in applications such as optical disk devices and laser beam printers, it is important to have stable fundamental transverse mode oscillation characteristics and a small astigmatism difference in the laser beam due to the need to focus the laser beam into a minute spot. . Further, in order to increase the speed of optical disk devices, laser beam printers, etc., a laser that operates with higher optical output is desired.

As such a semiconductor laser device, a semiconductor laser device shown in FIG. 10 has been devised. That is, on an n-GaAs substrate (5o), n-1no, 5(GaAf!
) P cladding layer (51), Anne 1-y y
G,5 doped In(GaAj7)P active layer 0.5 1-x x O,5(52),
P-In (GaAl2) Pri0
．． 5 1-y y O, 5 rad layers (53)
are sequentially layered. Furthermore, P-In (
Ga/l)-P cladding 0.5. 1-
On the y y O,5 layer (53), a P -1no,5(GaAjl)P optical waveguide layer (54
), Pl-zz O,5-In (GaAfl)
P(56), P-0,5t-y F O
, 5InGaP cap layer (56) is formed, and on this InGaP cap layer (5B), P-GaAs:
A ff contact layer (38) is formed, and an n-side electrode (5) is formed.
9), a P-side electrode (60) is formed. In this example, the AfI mixed crystal ratio is set to z −0,1%w =
By setting the value to 0.8, an attempt is made to obtain a lossless refractive index waveguide type semiconductor laser device.

However, in this case, P-In□,5(Ga
AN) P cladding layer (55) and n-1-3'
)' 0.5 The relationship of the specific 1-v v Ajl mixed crystal ratio with the 0.5 Ga Ajl As current blocking layer (57) and the specific implementation means have not been clarified, and it is desirable to extract the optimal conditions. It was rare.

(Problems to be Solved by the Invention) This invention has been made in consideration of the above circumstances, and its purpose is to
Beam ◆ Suitable for application as a light source for printers. Transverse mode control type VInGaA with small astigmatism difference and small cubic aspect ratio
An object of the present invention is to provide a J7P-based red semiconductor laser device.

The present invention also provides a transverse mode control type InGaAj7P red semiconductor that has a low operating voltage and therefore generates little heat during operation, and is suitable for high-output operation, which is important for increasing the speed of optical disks, memories, laser beam printers, etc. An object of the present invention is to provide a laser device.

[Structure of the invention]

(Means for Solving the Invention) The gist of the present invention is an InGaAf film formed on an n-type substrate.
In the 1P-based red semiconductor laser, by creating a change in the real refractive index in the lateral direction due to the presence of a layer with a high W refractive index in a part of the cladding layer formed on the side opposite to the substrate with respect to the active layer, This is to control the transverse mode without relying on loss waveguide.

Taking advantage of the fact that the following is small, InGaA
This is an attempt to reduce the element resistance, which was a drawback of the jpP red laser.

Moreover, the gist of the present invention is that p-GaAJ7 in contact with the active layer
To provide an Al mixed crystal ratio and a carrier concentration in the P-clad layer and the P-GaAlAs layer such that the voltage drop caused by the band discontinuity existing in the P-GaAj7'P layer is so small that it does not pose a practical problem. This aims to reduce the operating voltage of the element.

That is, the present invention is based on an n-type 1no, 5 (GaA
jl) P cladding layer (0x≦1-x
x O,5 1) and In(GaO,5t
-y1)? an active layer (O≦y<x), with at least P-type In (GaO,5
1-z 1) P first cladding layer (0x≦1) and zO05 equal to or greater than the In (GaO, 51-z Al2)P cladding layer formed thereon, zO,
5 In (Ga Aj) )0 with a small refractive index
．． 5 1-u u O,5P second cladding layer (0<z≦U≦1), and this In (Ga
Ajl) P 2nd crack 0.5 1-u
A stripe-shaped groove reaching the first cladding layer is formed in the uO,5 layer, and at least In(GaAN)P second cladding layer is formed in the groove. P-type Ga A47 As1-v with a larger refractive index than the layer
v Single layer or multiple P-type GaAj7A layers including a light guide layer
This is a semiconductor laser device characterized in that an s-layer is formed.

(Function) According to the present invention, the groove uO, formed in the In(Ga1-uo,5Ag)P second cladding layer
5 The refractive index of the Ga AI As layer in the outer layer is 1-
By making the refractive index larger than the v v layer, it is possible to realize a real refractive index difference large enough to control the transverse mode, so stable fundamental transverse mode oscillation is possible.

Furthermore, since the structure of the present invention is a real refractive index waveguide structure,
Compared to conventional loss waveguide structures, the width of the striped groove can be narrowed without significantly increasing the oscillation threshold current, making it possible to widen the beam radiation angle in the horizontal direction and achieve a small aspect ratio. . Further, since it is a real refractive index waveguide structure, a small astigmatism difference of 10 μm or less can be easily realized.

Furthermore, according to the present invention, a part of the P-type cladding layer serving as a current path is a P-type G with a resistivity lower than that of 1nGaARP.
Since it is replaced with aAj7As, the electrical resistance of the element can be reduced and the Joule heat generation amount can be reduced. Therefore, stable high-output operating characteristics can be achieved in the InGaApP red laser.

As described above, according to the present invention, optical disc devices and laser 3-
It is possible to realize an InGaAjlP-based red laser that has beam characteristics suitable for applications such as printers and is suitable for high-output operation.

(Example) FIG. 1(a) shows an InGaA example of j81 of the present invention.
FIG. 2 is a cross-sectional structural diagram of an flP semiconductor laser device. This semiconductor laser device has n-G a A 5cln-3,
Thickness: 1 μm) Undoped InO, 5Ga, P active layer (12) (Thickness: 0.08 μm), p-In
(GaAl) P cladding layer Q,5
0. $ 0.7 0.5 (13) (P −
5x 1017cI, -3, thickness 048m) is formed. On this P-In (GaO, 50, 3 AI') 0.7 0.5P cladding layer (13), there is a stripe in the center? -I n (Gao, 50.5°, ., , P light guide layer (14) (P -5xA
l) 17'-3 10'' Thickness $0.15''m > p-1no
, 5 (Ga AN ) P clarado layer (1
5) (PO, 30,70,5-s x 1017cII=3, thickness 0.6 μm) is formed. And these p-1no, 5(G a
0-5AI) P light guide layer (14> and P-0
,50,5 I n (Ga Aj! ,7') o, 5P
Clad 0.5 0.8 P-I no, 5 (GaO, 3
(n"lX10'C@-3, thickness 0.7 μm), this n-GaAs substrate buried layer 0.45 0.55 (Ga A,Q) 08) and P-1" 0.5 0 ．． SO,
70,5P cladding 1m (15) P-CiaA on top
s:I intact 8-3 layer (17) CP=2X10 am, thickness 2 μm)
is formed. In addition, on the back surface of the n-GaAs substrate (10), there is an n-side A u G e / A u electrode (18).
is formed, and a low refractive index layer (17) for P-current confinement is formed.
On the surface, there is an A u Z n / A u electrode (19
) is completely formed.

The semiconductor laser device shown in FIG. 1 is characterized by:
P-In (Ga Afri0.5 0.5
0.5 0.5P light guide layer (14> refractive index is n
-Ga casAfIO, 55A ss The refractive index is set to be larger than that of the buried layer (1B).

Figure 2 shows the refractive index n of GaAj7As and 1-xxIn(GaAN)P for wavelengths near the 670 nm oscillation wavelength of the laser in Figure 1.
The 0.5 1-x x O,5 relationship is shown for the AD mixed crystal ratio X. In addition, for InGaA and QP, when Int (G a x, -81)P,
It is sufficient that t satisfies 0,481 t≦0.25 that matches GaAs and the lattice X l-.

According to this, it is expressed as n G""As-3,82-0,73x, so the GaAs substrate buried layer is Aff mixed crystal ratio UL-u
It is sufficient to choose u so that u>o, as+0.23.

In the structure of FIG. 1, the refractive index difference between the stripe portion and the outside portion, represented by the width W in the figure, is Δn−
3X10-3 is obtained. This value was sufficient for controlling the transverse mode. Furthermore, since the n-GaAlAs buried layer (16) becomes transparent to the oscillation wavelength of 0.4 to 0.55 at this time, a real refractive index waveguide structure can be realized. The laser having the structure shown in FIG. 1 oscillated in the fundamental transverse mode when the stripe width W was 2.5 μm or less, and an isotropic beam radiation shape with an aspect ratio of 3 or less was obtained. Furthermore, an extremely small value of 5 μm or less was obtained for the astigmatism difference. Furthermore, in this example Ga Afl A
Since the s-buried layer (1B) 0.45 0.55 is n-type and serves also as a current confinement layer, a low oscillation threshold of 30 mA or less was achieved.

In addition, P-In (Ga AN) P
o, 5 0.5 0.5 0.5 light guide layer (1
4) stripe part and n-Ga AN outside it
Refractive index with As buried layer (1B) 0.45
0.55 Difference Δn and P-In (Ga AJ2) (
The range of stripe mW of the 1,50,50,50,5P light guide layer (14) will be explained. As shown in FIG. 3(a), as Δn increases, the stripe width in which fundamental transverse mode oscillation is possible (that is, the higher-order mode is cut off) becomes narrower. On the other hand, in order to maintain the mode stably even with current injection (IKA/cJ required for oscillation), Δn>IXIQ
-3 is considered necessary. On the other hand, the practical stripe width in terms of device fabrication process is considered to be 1.5 μm or more. If the width is narrower than this, it is difficult to form stripes by etching. Therefore, the practically useful Δn and W are 3-
2 IXIO<Δn<lXl0. 1.5μm<WS3.5
It is μm.

Here, P-In (Ga AJ2) 0.5
1-x Preferably, sulfuric acid is used.

P-I in heart
The A1 mixed crystal ratio of the n (Ga0.5 1-y Al)P1g Niclad layer is y 0.
5 P-In (Ga /47) P first crack 0.5 1-z z O
, 5 is required to be approximately equal to or smaller than the AfI mixed crystal ratio of the rad layer. Why does it fit, P-In (G
aA, Q) P second class 0.5 1-y y
The refractive index of the O,5 Rad layer is P-In (Ga0.
5 1-z Aρ ) z compared to the refractive index of the P first cladding layer
This is because if O15 is too large, the waveguide mode will be cut off. On the other hand, P-In, 5(Ga
Aρ ) Aρ1-z z of P first cladding layer
The O,5 mixed crystal ratio is set to z-0,5 due to the requirement to realize a potential barrier sufficient to confine carriers in the active layer.
It is desirable that there be at least one. Therefore, p-In (G
aAN) P second cladding 0.5 1-y
The Ail mixed crystal ratio of the y O,5 layer is also approximately y-0,5 or larger.

Figure 3(b) shows the etching rate A when using sulfuric acid.
It shows dependence on ρ mixed crystal ratio. The etching rate of InGaAlP shows a strong dependence on the Afl mixed crystal ratio, and the smaller the Afl mixed crystal ratio, the lower the etching rate. This situation was exactly the same even when phosphoric acid was used. Therefore, when the Aρ mixed crystal 1-x x O,5 ratio of the P-In,5(GaAN)P optical guide layer is smaller than x-0,3, the etching rate of the same layer and the Al mixed crystal P-In (Ga A!: Ri0.5 x
-y y Since the difference between the etching rate and the etching rate of the O,5P second cladding layer becomes too large, P-In (
GaO,5L-y 1) Side etching yO15 occurs in the PM Niclad layer, making it difficult to form a ridge. For this reason, in order to form a good ridge, P-In
(GaAN) P light guide 0.5
1-x x O, AJ7 mixed crystal ratio of 5 layers is x-0
, 3 is preferable.

Next, the buried GaAlAs layer will be explained. As shown in Figure 1(a), GaAj7 exposed in the air
A natural oxide film is formed on the surface of the As crystal. The thickness increases in proportion to the exposure time, but as in the actual crystal growth process, when the exposure time is several tens of minutes, Ag in the crystal increases.
The increase in oxide film thickness due to the increase in the mixed crystal ratio is remarkable. When a GaAlAs layer with a high AD mixed crystal ratio was used as the buried layer, the surface morphology of the P-GaAs layer grown thereon deteriorated, and this was particularly noticeable when the AR mixed crystal ratio was 0.8 or more. The reason for this is thought to be that the thickness of the above-mentioned natural oxide film becomes thicker. It is known that crystals with deteriorated surface morphology generally have many crystal defects, and such crystal defects multiply during long-term device operation, eventually reaching the active layer region and causing device deterioration. For these reasons, in order to obtain highly reliable devices, GaAl
It is desirable that the Al mixed crystal ratio of the As buried layer is less than 0.8, and up to 0.75 is good.

Furthermore, here, modified examples of FIG. 1(a) are shown in FIGS. 1(b) to (C). First, as shown in FIG. 1(b), P-
In (Ga AR) P Clara 0.5
0J O,70,5 do layer (15-1) and P-GaAs:) contact layer (17
) with an intermediate band gear knob between the two.
a A47 A s 0.5 0.5 may be used to form the easy current conduction layer (15-2). Further, the easy current conduction layer (15-2) may be a GaAl7As layer. In addition, the threshold value of the transverse mode control type semiconductor laser device can be lowered by 0.4 0.6. In addition, as shown in FIG. 1(C), P
-In(GaAl7)0.5
0.3 0.7 0.5P Clarado layer (15)
And P -1n (Ga
cao, 5 A, 1! ) P cladding layer (15〉 and P-Ga
AsO, 70,5 GaAl7 As or Gaa having a band gap intermediate to that of the contact layer (17-1), 40.
An easy current conduction layer (17-2) made of 0.5 0.5 AN A8 may be formed. As a result, the same effect as in the example of FIG. 1(b) can be obtained.

Furthermore, in FIG. 1(a), the cladding layer (15)
may be composed of GaANAsJm. In this case, n-
GaAlAs buried layer (16〉 and 0.45 0.5
5 P-GaAg As layer with substantially equal refractive index or 0.45
0.55 can be a P-GaAD As layer and 0.4
0.8 ru. In this way, the cladding layer (15), which becomes a current path, is
By forming with aAlAs, the resistivity can be lowered from 0.1 to 0.
．． 2Ω, it can be lowered by about 1 order of magnitude compared to the P-1nGaAIP layer, and as a result, the oscillation threshold current can be reduced by about 0.3V.

FIG. 4 is a diagram showing a method of manufacturing the InGaAlP semiconductor laser device shown in FIG. 1.

First, as shown in FIG. 4(a), an n-GaAs substrate (1
0> St-doped n-I n (G a O, a
O15 AQ) P cladding layer (11), undoped 0.7 0.5 In Ga P active layer (12), Znn doped-0,50,5 In CGa AN) P cladding layer 0.5 0J O,70,5 (13), Zn-doped P
-1n (Gao, 50.5 AN) P light guide II (14) and Z
n-doped 0.5 0.5 P-un (Ga A1) P Clara Q, 5 0.3 0.7 0.5 do° layer (1
5> are sequentially grown and formed. Crystal growth was performed by low pressure metal organic chemical vapor deposition (MOCVD). Next, a 5t3N4 film (20) with a thickness of 100 OA is formed in a stripe shape, and using this as a mask, P-In (Ga A
j) ) Po, 5 04
O,70,5 cladding layer (15) and P-In (
Gao, 50.5 Ag) P light guide layer (14) is P-1n
, 50.5 0.5 (Ga AN ) P cladding layer (13)
0.3 0.7 0.5 to form a convex mesa (FIG. 4(b)). At this time, if an (ioo) substrate is used and the stripe direction is set in the (011) direction, an inverted trapezoidal (inverted mesa) convex portion is formed, which is advantageous because the width near the active layer can be narrowed. Next, s i3N 41I(2
0) as a mask, St-doped n-GaAlAs buried layers (
18) was grown selectively. Growth temperature is 700℃, pressure is T5To
rr, and under this condition S L 3 N 4 Wj4(2
0.45 0.55 Good selective growth was performed without the Ga AN Ag layer being buried on the 0.45 0.55 layer (FIG. 4(C)).

Also, Ga AN2 As (0<X<1) is L
-x x Even if the A and Q compositions of the crystal change with respect to different growth plane orientations, the resulting change in the lattice constant is extremely small, so lattice mismatch also occurs on the side surfaces of convex parts that have plane orientations different from the substrate surface. Good Ga
A, Q AsGA could be grown at 1-x x.

Furthermore, after removing the Si3N4 film (20) by etching, a Zn-doped P-low refractive index layer (17) for current confinement was grown again by low-pressure MOCVD, and an n-type A
An InGaANP-based red semiconductor laser device, which is an embodiment of the present invention, shown in FIG. In the above-mentioned manufacturing method, when the Sl-doped n-GaApAsO, 450,55 buried layer (18) is formed by low pressure MOCVD using the 513N4 film (20) as a mask, the 513N4 film (20) is GaO,45/J?
Good selection without depositing As layer 0.5
However, in order to perform this selective growth well, it is necessary to limit the AJ2 mixed crystal ratio of the GaARAs buried layer (16). That is, Ga A, 17 As forming the buried layer (1B), A, l) mixed crystal ratio 1
-x x As X becomes larger, S i 02m1! (20) A GaAllAs layer is also deposited on top of the S t 02 film (2
0) becomes difficult to remove, making it impossible to obtain a good transverse mode control type semiconductor laser device. The inventors of the present application,
InGaAIP formed with a 5lO2 mask with a width of 5 μm
When a GaAJ7As layer of 1-x x 0.5 .mu.m was grown on a substrate, the presence or absence of deposition on a mask was investigated by experiment, and the results were as shown in Table 1 below.

The following margins, that is, in the case of GaAs, GaAl70.45
In the case of 0.55 As and GaAl7As, no deposition was observed on the 0.25 0.75 S io 2 mask, and a transverse mode control type semiconductor laser device could be successfully obtained. Ta. In addition, in the case of Ga Aρ As, part 0.25
0.75 Publicly deposited. However, in this case GaO, 25A
The deposition of the I As layer is partial and S t O20
, 75 There was no problem in removing the mask, and a good transverse mode control type semiconductor laser device could be obtained. moreover,
Ga Af! In the case of As, a GaAfIAs layer is deposited on the entire surface of the 0.2 0.8 SiO2 mask,
Subsequent removal of the 5IO2 mask was difficult, and a good transverse mode control type semiconductor laser device could not be obtained. Therefore, the AfI mixed crystal ratio X of the Ga AjJl-x x As buried layer must be X≦0.75, and as a result, I n (G a s
．． 5 1) The Al7 mixed crystal ratio U of the Ga, uAJ7uAs buried layer v O05 with respect to the Al mixed crystal ratio W of the P light guide layer is 0.48w + 0.23< u≦0.75.

FIG. 5 shows InGaAj7 which is a second embodiment of the present invention.
FIG. 2 is a cross-sectional structural diagram of a P-based semiconductor laser device. That is,
n-In (Ga
AfI)? Cladding 0.5 0.3
0.7 0.5 layer (21) (n = 4 x 1
0'cm-3, thickness 1μm), undoped In
Ga P active layer (22) (thickness 0.5 0.5 0.06 μm) P In (GaO, 30, 5 1) P layer 11 with a striped convex part (convex part) in the center (23)(P-5xO,7
0,5 1017cII-3, thickness 1 μm) were formed sequentially (G
I am a. Furthermore, this p' −■”0.5 0.3A
p) P club 11 layer (23) strike 0.
7 0.5 Opposite conductivity type n-Ga on both sides of the square ridge.
Al1As buried layer (26) (n −1xO
, 350, 85 1017CII+-3, thickness 0.8 μm) is embedded. And these P-1no4 (Ga
, 3All) P class 11 layer (23) and n
-G ao, a sO,70,5 Al1 As on the buried layer (2B) is P-0
,65 Low refractive index layer for current confinement <27) (P -2X
1018 am-3 (thickness 2 μm) is formed on the back side of the n-GaAs substrate (lO).
/Au electrode is formed on the surface of the low refractive index layer (27) for P-current confinement.
A u electrode is formed.

In addition, in FIG. 5, P −1n (G a o, a
O05 1') P Clara de layer (23) striped 0.7 0.5 The thickness on both sides of the ridge portion is 0.2 μm.

In the 1nGaAfIP semiconductor laser device shown in FIG. 5, Ga A47 As and 1-X shown in FIG.
x In (GaAN) From the relationship of refraction 0.5 L-x x O, 5 index with P, P-I n (Ga o, ao, 5 Ajl)
The Ag composition of each layer is set so that the refractive index of the −0,70,5 G a Ajl As buried layer (2G) is 0.35 0.85 larger.

As a result, it is possible to achieve a refractive index difference between the stripe portion and the outside portion of Δn > l In this case, a small aspect ratio of less than 3 was obtained.In addition, the astigmatism difference was 5.
A small value of less than μm was obtained.

Furthermore, in this example, Ga Aρ As filling 0.3
5 0.65 Since the filling layer (26) is of n-type and serves also as a current confinement layer, a low oscillation threshold of 30 mA or less can be achieved.

FIG. 6 is a diagram showing a method of manufacturing the InGaAj7P semiconductor laser device shown in FIG. 5.

First, as shown in FIG. 6(a), an n-GaAs substrate (1
0), Si-doped n-In (GaO150,3Ajl)P layer 11 (21), undoped 0.7 0.5 InGaP active layer (22〉), Znn-doped -0,50,5 In (Ga AN) Pkura 11
Layers 0.5 0.3 0.7 0.5 (23) are grown in sequence. Crystal growth is performed using low pressure organometallic vapor phase epitaxy (
MOCVD method).

Next, a 100OA thick Si3N4 film (
20> and using this as a mask, P-In (
Ga Ajl) Pkura 11 layer 0.5
Q, 3 0.7 0.5 (23) is removed by etching leaving only a thickness of about 0.2 μm on the active layer (22) outside the stripe to form a convex mesa (6th
(Figure (1))) At this time, if a <100) substrate is used and the stripe direction is set in the (Oll) direction, an inverted trapezoidal convex portion is formed, which is advantageous because the width on the active surface can be narrowed. .

Next, the pressure is reduced again using the Si3N4 film (20) as a mask.
St-doped n-Ga is deposited on both sides of the convex portion by OCVD method.
Select Aj7As buried layer (26) 0.35 0.8
5. Growing selectively. Growth temperature is 700℃, pressure is 75T
orr (Fig. 6(b)), and furthermore, S i
After removing the 3N, i film (20) by etching, a Zn-doped P-low refractive index layer (27) for current confinement is grown again by low-pressure MOCVD, and the AuGe/A layer on the n-side is grown.
u electrode 28〉 and P side A u Z n / A
By forming the u electrode (29), an InGaAρP red semiconductor laser device as an example of the present invention shown in FIG. 5 was completed.

Note that the present invention can be implemented with various modifications without departing from the gist thereof.

FIG. 7 shows a third embodiment of the present invention.
FIG. 2 is a cross-sectional structural diagram of a P-based semiconductor laser device. This semiconductor laser device is manufactured by first disposing an n-GaAs substrate (10) on an n-GaAs substrate (10).
1nGaP club 0.5 0.5 7-3 do layer (31) (n-4X10 am, thickness 1μm
), undoped InGaP active layer (32) 0.
5 0.5 (thickness 0.06 μm) P −I n ,
(GaO, 50, 3 A, 9) P first cladding layer (33) (P
-5xO, 70, 5 7-3 100111, thickness 0.2 μm) are sequentially formed. This P-In (GaAl2)0
．． 5 0 J 0.7 0.5 On the PP1 cladding layer (33), a second cladding layer ((4) ( n-4X10'0.5 (2)-3, thickness 0.6 μm) is formed. Also, this n-In Ga Al7 P second cladding layer (34> Upper and n-1nAIP No. 20.5
0.5 Thin P-
GaAl7As light guide layer (35) P −
2xO,40,6 8-3 10cm, thickness 0.15μm) is formed, and this P-G
a On the AfI As light guide layer (35), 0
．． 4 0.6 P-Ga so as to fill the above striped grooves.
AN As cladding layer (H) (P -2xO,3
0,7 8-3 10 cm, thickness 1 μm), and on top of this a P-GaAs:l contact layer (37) (P-2
8-3 XlOcm, thickness 2 μm) are sequentially provided. still,
On the back side of the n-GaAs substrate (1o), the n-side A u G
An e/Au electrode (38) is formed, and a P-side AuZ layer is formed on the surface of the low refractive index layer (37) for P-current confinement.
An n/Au electrode (39) is formed respectively.

The semiconductor laser device shown in FIG. 6 is characterized by n-1n
Aj? P second layer 1 layer (34) 0.5
0.5 P −Ga o formed in the drive-shaped groove, 4
The refractive index of the Aff As optical guide layer (35) is 0.6, and n=In ARP on both sides of the live groove is 0.5.
The refractive index is set to be larger than that of the 0.52 cladding layer (34).
ANAs and I n (
Ga 1□1-x x O,5 1) From the refractive index relationship with P, P-Gax O,
5 The A,17 mixed crystal ratio of the Aj7As light guide layer (35) is o,
e, and A of the n-1nAl7P second cladding layer (34)
, the Q mixed crystal ratio is set to 0.5. I n (G a
1-uO05 1) Aρ mixed crystal ratio U of the P second crystal 1 layer is u O95 to AJ7 mixed crystal 1-v v of the Ga AI As optical guide layer. From FIG. 2, the ratio V is v < 0.48 u + It should be selected so that it becomes 0.23.

In the structure shown in FIG. 7, the refractive index difference between the stripe portion represented by the width W in the drawing and the outside portion is Δn-5.
A value of X10', which is large enough to control the transverse mode, can be achieved. In the laser having this structure, stable fundamental transverse mode oscillation was obtained when the stripe width W was 2 μm or less, and isodirectional beam radiation characteristics with an aspect ratio of 2.5 or less were realized. Furthermore, because of the real refractive index waveguide structure, the beam astigmatism difference was also extremely small, 5 μm or less.

Here, P I n (G a A fl
z) o, 50.5 1-z P first cladding layer and P-GaAl7As optical layer 1-v
v At the heterojunction interface of the id layer, there is a band discontinuity in the valence band, which acts as a barrier to holes, causing a voltage drop, resulting in an increase in the operating voltage of the device. This band discontinuity in the valence band increases or decreases depending on the mixed crystal ratio of both AfI, and P-In (Ga
Al7) P 1st 0.5 1z
z O,5 The Al7 mixed crystal ratio of the cladding layer is small, and P-G a 1-
vAρ, it was found that the larger the Aρ mixed crystal ratio of the As optical guide layer, the smaller the band discontinuity.

PI in heart
n (G a 1-20.5 AN2). The AfJ mixed crystal ratio of the sP first cladding single layer needs to be at least zmO,5 or more in order to realize a potential barrier sufficient to confine carriers in the active layer. Therefore, P-In (G
a AN ) P first 0.5
0.5 0.5 0.5 For rad layer, P-Ga
A[As photoguide 1-v v Elements were fabricated with various AR mix ratios in the guide layer, and their current-voltage characteristics were investigated. The results are shown in FIG. 8(a). According to this, P-Ga Al71-v
It can be seen that a sufficiently low operating voltage can be obtained when the Al mixed crystal ratio V of the v As optical guide layer is 0.4 or more. For these reasons, in order to achieve favorable current-voltage characteristics, P
-GaAl7As light guide 1-v The Ag mixed crystal ratio V of the v v layer needs to be at least 0.4 or more.

Now, in the example of the structure shown in FIG. 7, P -1n (G a Afl2) o, 5P of zamO07
For the 0.5th 1-z-cladding layer, P-GaAj7Asl-v
v Creating devices with various Afl mixed crystal ratios in the light guide layer,
When its current-voltage characteristics were investigated, the results shown in FIG. 8(b) were obtained. According to it, P-Ga Al
7 AfJ mixed crystal ratio V of the As optical guide layer is 1-v
It can be seen that a sufficiently low operating voltage can be obtained when v is 0.6 or more. In fact, in the structure shown in Fig. 7, P-Ga A
The l mixed crystal ratio V of the l1 As light guide layer is 1-v
V is set to 0.6, so during laser oscillation operation (J
It was possible to drive at a low voltage below ~2 kA/cd) (=2.5 VJd).

Additionally, a P-GaARAs optical guide layer of 0.4 0.8 (35) and a P-GaAjlAs cladding layer of 0.3
The resistivity of 0.7 (3S) is 0.1 to 0.2Ω, and P
- Since it is about one order of magnitude lower than the InGaAlP layer, the P-In
Compared to a semiconductor laser device with a conventional structure in which only a GaAlP layer is used as a cladding layer, the oscillation threshold current was reduced by approximately 0.3V.

In addition, the A, Q mixed crystal ratio of the P-GaAIAs cladding layer 0.3 0.7 (36) is such that its refractive index is n-1n, 5
1 P 0 which is almost equal to the second cladding layer (34)
, 5, set it as 0.7. By doing this, it was possible to produce a change in the real refractive index that was large enough to control the transverse mode.

These make it possible to minimize the amount of heat generated by the element even during high-power operation with high current density.
Good high-output characteristics were achieved without a decrease in differential quantum efficiency due to heat generation up to a CW optical output of 20 mW or more.

Furthermore, in this example, In AI P No. 20.5
0.5 Crud! By making (34) n-type, a structure was created in which it functions as a current confinement layer so that current flows only through the stripe portion, and a low oscillation threshold of 30 mA or less could be achieved.

FIG. 9 shows an InGaAlP film showing a fourth embodiment of the present invention.
FIG. 2 is a cross-sectional structural diagram of a semiconductor laser device. This semiconductor laser device first has an n-GaAs substrate (40) on which an n-
InARP Cla 0.5 0.5 7-3 Rad layer (41) (n = 4 X 1 G Cal
s thickness 1 μm) Undoped In AI
P active layer 0.5 0.5 (Ga (42) (thickness 0.06 μm), P I n
o, 5o, 3Af! ) P first cladding layer (4
3) (P-5XO, 70, 5 7-3 10 cm, thickness 0.2 μm) are formed in sequence. This P-In (GaAfl)0.5
On the 0.3 0.7 0.5P first cladding layer (43), an n-1no, 5AIP second cladding layer (43) of opposite conductivity type is formed on both sides except for the central striped region.
4) (n = 4 x O15 7-3 10 cm, thickness 0.6 μm) is formed.

Also, this n-1nAJ7P second clad 0.50
．． 5 layers (44〉on the surface and n-1nA, QP second layer 0.5
0.5 In the stripe-shaped groove between the rad layers (44), P-Ga
Aj? As light guide layer (45) (P −
2XO, 350, 85 1018cIn-3, thickness 1.2 μm) is completely formed, and on top of this, a low refractive index layer (46
) (P-8-3 2×10C1l, thickness 1.2 μm) is formed.

In addition, on the back side of the n-GaAs substrate (40〉), the n-side A
A uGe/Au electrode (47) is formed and P
- A P-side AuZ n /Au electrode (48) is formed on the surface of the low refractive index layer (4B) for current confinement.

The semiconductor laser device shown in FIG. 9 is characterized by n-1n
ARP second cladding layer (44) 0.5 0.5 P -G ao,a formed in the drive-shaped groove part
The refractive part of the 5AgAs light guide layer (45〉)
85 n-1n on both sides forming a striped groove. ,5Ag
The refractive index of the P second cladding layer (44〉) is set to be 0.5 larger than that of the second cladding layer (44〉).
-x
5 A, the Aj7 mixed crystal ratio of the 17As optical guide layer (45) is set to 0.
65, and the A and Q mixed crystal ratios of the n-1nAj7P second cladding layer (44) are 0.5.

By doing this, the effective refractive index difference Δn between the stripe portion represented by the width W in the figure and the outside portion
>lXl0-3, which is large enough to control the transverse mode, could be achieved.

In a laser with this structure, when the stripe width W is 2 μm or less, stability is achieved with fundamental transverse mode oscillation and an aspect ratio of 2.
An isodirectional beam radiation characteristic of less than 5 was achieved. Furthermore, the beam astigmatism difference was also extremely small, 5 μm or less.

Furthermore, by adopting a P-GaAIAs optical guide layer 0.35 0.85 (45), during laser oscillation operation (J~2KA/
cj ), it was possible to drive with a low voltage of 2.5 V or less. As a result, good high-output characteristics could be achieved without a decrease in differential efficiency due to heat generation up to a CW optical output of 20 mW or more. Further, since the InAlP second cladding layer (44) is of n-type and has a current confinement layer of 0.5 0.5, a low oscillation threshold of 30 mA or less can be achieved.

It should be noted that the present invention can be modified in various ways without departing from the spirit thereof.

[Effects of the Invention] As described above, the present invention has stable fundamental transverse mode oscillation characteristics, a small aspect ratio, and a small astigmatism difference, and is suitable for applications such as optical disk devices and laser beam printers. InGaA with beam characteristics and high reliability
A j7P-based red laser can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram of a semiconductor laser device showing a first embodiment of the present invention, and FIG. 2 is an Ino, 5 (GaAN) semiconductor laser device.
and Ga AJl-x x O,5
1-x Diagram showing the relationship between the refractive index of xAs, 3rd
The figure shows the relationship between the refractive index difference Δn and the stripe width at which higher-order modes are cut off, and the etching characteristics. Figure 4 is a diagram showing the manufacturing method of the semiconductor laser device shown in Figure 1. , FIG. 5 is a cross-sectional structural diagram of a semiconductor laser device showing a second embodiment, FIG. 6 is a diagram showing a method of manufacturing the semiconductor laser device shown in FIG. 5, and FIG. 7 is a diagram showing a third embodiment. FIG. 8 is a cross-sectional structural diagram of a semiconductor laser device, and FIG. 8 is a diagram showing current-voltage characteristics as a semiconductor laser device. FIG. 9 is a cross-sectional structural diagram of a semiconductor laser device showing the fourth embodiment.
FIG. 0 is a diagram showing a conventional example. 10...GaAs substrate, 11.21.n-
In (Ga AN) Pkura 11
Layer, 0.5 0.3 0.7 0.512.22
...Undoped In Ga P activity 0.5
0.5 layer, 13, 23...P-n (Gao, 30.5 Ag) P-cla 11 layer, 14...P-0,
70,5 In(GaAjl)P light guide layer, 0.5 0.5 0.5
0.515...P-In (Ga/
j) ) PO, 50, 30, 70,
5 Cladding layer, 16-n-Ga AN As buried 0.45 0.55 Inlaid layer, 17.27...P- Low refractive index layer for current confinement, 18- AuGe/Au electrode, 19- A u
Zn/Au electrode, 20...SiO2 film, 26-
n-Ga Ag As buried layer. 0.35 0. [i5 Embedded Patent Attorneys Kensuke Norichika and Mitsuyuki Matsuyama 0 0.5 A1 Sekihiro 1 Fig. 2 0 θ 1θ A@1rll bn (x-to-”) Illustrated Country Camellia 6 Voltage ■ [V] Figure 8 1 Voltage■

Claims (10)

[Claims] (1) A refractive index waveguide type semiconductor laser device in which a striped high refractive index layer is provided on the cladding layer of a double heterojunction structure in which an active layer is sandwiched between cladding layers, and the high refractive index layer is Int(Ga_1_−_wAl_w)_1_
−_tP (0.48≦t≦0.52), and the low refractive index layers on both sides of the high refractive index layer are Ga_1_−_uAl_
When consisting of uAs, 0.48w+0.23<u≦0.7
A semiconductor laser device characterized by having a relationship of: 5. (2) A double heterojunction structure provided on a GaAs substrate, in which an InGaP active layer is sandwiched between InGaAlP cladding layers, a striped high refractive index layer provided on one of the cladding layers, and this high refractive index layer. A refractive index waveguide type semiconductor laser device comprising a low refractive index layer for current confinement provided on both sides of the layer, and a GaAs contact layer provided on the high refractive index layer and the low refractive index layer. Yes, and the high refractive index layer is Int(Ga_1_-_wAl_w)_1_
-_tP (0.48≦t≦0.52), and when the low refractive index layer is made of Ga_1_-_uAl_uAs, 0
．． A semiconductor laser device characterized by having a relationship of 48w+0.23<u≦0.75. (3) An InGaAlP layer is provided on the high refractive index layer, and a GaAlAs layer having a band gap between these layers is provided between this InGaAlP layer and the GaAs contact layer. 3. The semiconductor laser device according to claim 2. (4) A refractive index waveguide type semiconductor laser device in which a striped high refractive index layer is provided on the cladding layer of a double heterojunction structure in which an active layer is sandwiched between cladding layers, and the high refractive index layer is Ga_1_-_uAl_uAs, and the low refractive index layers on both sides of the high refractive index layer are Int(GaA_1
____wAl_w)_1_-_tP(0.48≦t≦0
．． 52) A semiconductor laser device characterized by having the relationship u<0.48w+0.23. (5) A double heterojunction structure provided on a GaAs substrate, in which an InGaP active layer is sandwiched between InGaAlP cladding layers, a striped high refractive index layer provided on one of the cladding layers, and this high refractive index layer. A refractive index waveguide type semiconductor laser device comprising a low refractive index layer for current confinement provided on both sides of the layer, and a GaAs contact layer provided on the high refractive index layer and the low refractive index layer. The high refractive index layer is made of Ga_1_-_uAl_uAs, and the low refractive index layers on both sides of the high refractive index layer are made of Int(Ga_1_
-_wAl_w)_1_-_tP(0.48≦t≦0.
52) A semiconductor laser device characterized by having the relationship u<0.48W+0.23. (6) The semiconductor laser device according to claim 2 or 5, wherein the forbidden band width of the low refractive index layer is wider than the forbidden band width of the active layer. (7) The cladding layer is In_0_. _5(Ga_1_
-_ZAL_Z)_0_. _ Consists of 5P, u>0.4
6. The semiconductor laser device according to claim 2, wherein the semiconductor laser device has a relationship of 8z+0.23. (8) The high refractive index layer is provided on the striped groove of the low refractive index layer and on the low refractive index layer, and GaAlAs is formed between the high refractive index layer and the GaAs contact layer.
6. The semiconductor laser device according to claim 5, further comprising a layer. (9) A first InGaAlP cladding layer, an InGaP active layer, and a second InGaAlP cladding layer are sequentially stacked on a GaAs substrate to form a double heterojunction structure, and an InGaAlP cladding layer is stacked on the second InGaAlP cladding layer.
1_-_wAl_w)_1_-_tP(0.48≦t≦
0.52) A high refractive index layer is formed, and this Int(Ga_1
_-_wAl_w)_1_-_tP high refractive index layer is partially etched to form a stripe shape, and this stripe-like Int(Ga_1_-_wAl_w)_1_-_
Ga_1_- for current confinement on both sides of the tP high refractive index layer
_UAL_UAs(0.48w+0.23<u≦0.7
5) A method for manufacturing a semiconductor laser device, characterized in that a low refractive index layer is formed, and a GaAs contact layer is formed on the high refractive index layer and the low refractive index layer. (10) A first InGaAlP cladding layer, an InGaP active layer, and a second InGaAlP cladding layer are sequentially stacked on a GaAs substrate to form a double heterojunction structure, and an InGaAlP cladding layer is formed on the second InGaAlP cladding layer. −＿
wAl_w)_1_-_tP(0.48≦t≦0.52
) a low refractive index layer, and this Int(Ga_1_-_w
Al_w)_1_-_tP The low refractive index layer is partially etched to form striped grooves to form a current confinement part, and Ga_1_-_uAl_u is formed in the striped grooves.
An As (U<0.48w+0.23) high refractive index layer is formed, and a G
A method for manufacturing a semiconductor laser device, comprising forming an aAs contact layer.