JPH02213183A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce astigmatism by providing a region of a low retractive index on the lateral sides in the vicinity of a stripe-shaped active layer by diffusing impurities of a second conductivity type from the surface of an (AlxGa1-x)InP clad layer of the second conductivity type having a projecting part, in a double hetero structure constructed of an (AlxGa1-X)InP clad layer of a first conductivity type, an InGaP active layer and said clad layer of the second conductivity type formed which are formed on a GaAs substrate of the first conductivity type. CONSTITUTION:An (AlxGa1-x)InP clad layer 13 of a first conductivity type (0<x<=1), an (AlyGa1-y)InP active layer 14 (0<=y<x, z) and an (AlzGa1-z)InP clad layer 15 of a second conductivity type (0<z<=1) having a stripe-shaped projecting part are formed on a substrate 11 of the first conductivity type, so that a double hetero structure be constructed. Impurities of the second conductivity type are diffused from the surface on the lateral sides of the projecting part of the clad layer 15 of the second conductivity type and on the outside of said projecting part into the active layer except the part of this layer just under the projecting part and into the clad layer 13 of the first conductivity type, and thereby a region 20 is formed. According to this constitution, a difference in the refractive index in the horizontal direction can be made large for junction in the vicinity of the active layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser that oscillates in the visible light region and a method for manufacturing the same.

Conventional technology (AlxGaIK"'t-X)0.5"0.5
The P-based compound semiconductor device is a direct transition type device that is lattice matched to a GaAg substrate, and the forbidden band width can be varied while changing the composition X in the range from 1.9 eV to 2,36 V. For this reason.

A double heterostructure semiconductor laser using this mixed crystal system is an attractive material that emits light at a wavelength of 0.68 μm to 0.58 μm, and has been actively researched and developed recently. Since this type of semiconductor laser has a short wavelength, it is considered promising as a light source for compact disks and optical disks that aim to improve recording density.

As an example of this type of semiconductor laser, a red laser with a wavelength of 670 .mu.m has been obtained with the structure shown in FIG. 4 (20th Confluence of Element Materials, D-3-3, 1988).

11 is an n-type GaAs substrate, 12 is an n-type OAM S buffer 1
Layer, 13ban type (AlxGaIG, 7G S) 0.
5”0.S P cladding layer, 14 is Kn Ga
P active layer, 15 is p type (AlxGa"0.7"0,1
)0, 5o, s o, s Xn P cladding layer, 16 is p-type Ino, Gao, P
layer.

17 is a p-type Ga 8 buried layer, and 18 is an n-type electrode.

19 is a p-type electrode. This structure is characterized by a mesa portion provided in the p-type rad layer 16 and an active layer 14 provided outside the mesa.
The p-type CaAs layer 17, which has a larger refractive index, creates an effective refractive index difference in the horizontal direction with respect to the junction.
The As layer serves as a light absorption layer, suppressing higher-order modes and stabilizing transverse modes. Therefore, high output is possible and stable photo-current characteristics are obtained. The growth of this device is generally performed by low pressure metal organic vapor phase epitaxy (MOVPE). However, since this element is an antiphase refractive index waveguide type using an absorption layer, the output angle is generally 7 to 8 degrees in the horizontal direction and 30 to 40 degrees in the vertical direction, and the beam shape is elliptical. Similar to striped lasers, astigmatism is approximately 4
It is large, 0 μm, and is difficult to use as a recording light source for optical discs, compact discs, etc.

Problems to be Solved by the Invention As described above, the conventional technology has a problem in that the AlGa1nP semiconductor laser has a large astigmatism because it is of the antiphase index guided type.

Means for Solving the Problems According to the present invention, (AlxGa1xGa, -x) InP of a first conductivity type is formed on a substrate of a first conductivity type.
, de layer (0<)C≦1).

(AlyGa1-,)InP active layer (0≦y<x, z)
and a second conductivity type (A
lxGal, Ga, -,) InP cladding layer (0<
z≦1), from the side surface of the convex part of the second conductivity type 5-rad layer and the surface outside the convex part, the active layer excluding the active layer directly under the convex part, and the active layer 1
This semiconductor laser includes a region in which impurities of a second conductivity type are diffused into the cladding layer of the second conductivity type. Further, the manufacturing method is Movpx method, and the growth temperature of the active layer is in the range of 630°C to 700°C.

Effect: By using the means according to the present invention described above, a refractive index guided semiconductor laser can be easily obtained, and not only a stable single transverse mode can be obtained, but also the emission angle remains unchanged at 30 to 40' in the vertical direction. The horizontal direction is increased to 16 to 20 degrees, improving the aspect ratio, and the astigmatism is improved to a few micrometers. Furthermore, the growth temperature of the active layer was changed from 630'C to 700'C.
By growing within the C range, it is possible to create a larger horizontal refractive index difference with respect to the junction near the active layer, resulting in highly stable single mode oscillation and low astigmatism. A semiconductor laser is obtained.

Example (Example 1) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a ψ plane view of the structure of the semiconductor laser of the present invention. Note that the numbers in FIG. 1 are the same as in FIG. 4 of the conventional example to simplify the explanation. , 11 is n-type OAM substrate, 12 is n
Type QaAs batt 7 layer (thickness d ~ 0.5 μm, carrier concentration in ~ IXl 018cyx''), 13 is n type (A
lxGal, Ga, -,) XnP crat layer ((
1~1 μm, n~5X1 o17c=*-3)
14 is an InGaP active layer (d~0.1 am, undoped), 15 is a normal mesa-shaped p-type (AlxGaeX"
1-X) InP layer ((INo, 7 μm
, p ~ 5 x 10''clll-3), 16 is a p-type InGaP layer (d ~ 0.511 m).

p~2X1018i”1l-5)l11 Company T p type GI
Lm 8 contact layer (d~3μ@, p~3X10'
8CM').

18 is n-type MuGe/Ni electrode, 19 is p-type MuZ
It is an n-electrode. In addition, a p-type Zn diffusion layer (depth 1 μm, p~5X10”1-5) diffused from the surface of the p-type cladding layer.
is formed like the first @.

The thickness of the p-type InGaP layer 16 is 3 μm. Therefore, the stripe width of the mounted active layer without Zn diffusion is about 2 μm.

The current path in the device shown in Figure 1 is made of p-type Ga, which has a small heterobarrier.
The p-type Rrad layer 15. It is implanted into the InGaP active layer 14. This is because the p-type InGaP layer 18 reduces the electrical resistance between the p-type GaM S contact layer 17 and the p-type cladding layer 17 . The structure shown in FIG. 1 is characterized by the fact that, like the conventional structure shown in FIG.
carried out by The leading wave is generated in the cladding layer 16 formed in a striped mesa. The tDP type diffusion layer 20 is a highly doped p-type region 100 in the active layer 14.
A difference in refractive index occurs between the undoped region 101 and the undoped region 101 . The refractive index of the undoped layer is 1 for the wavelength 870nlE1.
01 is 3.58. The high concentration layer 1ω is 3.67, and the high concentration p
The refractive index of the type reconnaissance area is about 3x10, which is 1 degree smaller.
The structure of the present invention is an m-index waveguide laser, unlike the conventional structure. Therefore, unlike the anti-refractive index waveguide type, the wavefront of light guided not only in the vertical direction but also in the horizontal direction with respect to the multi-junction is not bent, and the emitted light is ideally diffracted at the resonator end face. Therefore, astigmatism can basically be kept small. The characteristics of the actually manufactured device are that the threshold current is 60 rI.
The output angle is 10" or more in the horizontal direction and 306" in the vertical direction.
An astigmatism of 10 μm or less was obtained. On the other hand, FIG. 2 shows an n-type G&M S current blocking layer 21 on the p-type raw layer.
has been established.

This serves to prevent current from flowing to areas other than the active layer when driven at a high voltage, and is advantageous when operating at a high output.

Next, a method for manufacturing a structure according to an embodiment of the present invention will be described with reference to FIG. First, in Figure 3 (!L), mov
N-type G1 S substrate 11 using px method or MBE method
N-type GILA on top! i-bar, F layer 12°, n-type cladding layer 13, InGILP active layer 14. A p-type cladding layer 16 and a p-type InGIP layer 16 are formed. Next, the third
5iO2J stripes with a width of 3 μm are formed by photolithography as shown in Fig. 2). In FIG. 3(c), the p-type InGaPR 1e and the p-type cladding layer 15 are mesa-etched using a sulfur-based solution. Then, in 3-machi, S
Using xOz+i 22 as a mask, Zn is diffused from the mesa etched surface to form a diffusion layer 20 with a depth of about 1 μm.

The Zn diffusion conditions were as follows: the diffusion source ZnP2 and red phosphorus were sealed together with shrimp in a quartz ampoule under vacuum (vacuum degree <I
This was done in 0 minutes.

After that, the heat-damaged layer on the diffusion surface is lightly etched with a H2504-based solution, and then the wafer is immediately introduced into a growth chamber, where a p-type G&M S layer 17 is buried and grown as shown in FIG. 3(6). Finally, as shown in FIG. 3(f'), electrodes 19 and 20 are formed, and the manufacturing process is completed.

(Example 2) Next, a second embodiment of the present invention will be described.

When growing InGaP using organic gold 1 vapor phase growth method.

It has been reported that the forbidden band width varies depending on the growth temperature even if the grain composition is the same. For example, 5 Ming et al., Applied Fixtures Letters Vol. 60, P, θ73 (1987). In this paper, crystals grown at a growth temperature of around 660° C. exhibit regularity in the arrangement of Ga and In on the group II sublattice, forming a so-called natural superlattice (ordering). In fact, compared to the case of random arrangement (disordering), the forbidden band width is about 5 QmeV smaller. In our fourth experiment, the growth temperature at which ordering occurred was 630 to 700'C. Therefore, in the structure of the first embodiment of the present invention shown in FIG.
When grown in the vicinity of so'c, an ordered crystal structure is obtained, and the Zn diffusion region 2o is formed by Zn diffusion.
The crystal structure of the active layer 14 therein collapses and becomes disordered. Therefore.

A refractive harmonic wave structure is obtained in which so-called low refractive index regions with a large forbidden band width are formed on both sides of the active layer 14 in the mesa stripe. The effective refractive index difference is eoo°C due to Zn diffusion.
When carried out with
, wavelength e70μrrt, cladding layer set Ff, X=
When it is 0.6, it becomes about 8×10 2 , which is the same as a normal embedded structure. Therefore, it is not only possible to control the horizontal emission angle with respect to the junction, but also it is possible to manufacture a semiconductor laser with small astigmatism because it is of the refractive index waveguide type. When a device was actually fabricated, the stripe width of the active layer 14 having an ordered crystal structure was 2 μm, the threshold current was 601 μm, and the output angle was 16 to 2 μm in the horizontal direction. An element closer to a perfect circle in the vertical direction 30' than conventional elements and with a low astigmatism of 1 to 2 μm was obtained. In addition, the optical output characteristics with respect to current were improved, and the characteristics were stable in the ram mode even at high current injection.

Effects of the Invention As described above, first, (AlxGa')C"1-X)1 of the first conductivity type is deposited on the GaAg substrate 1 of the first conductivity type.
An nP cladding layer, an InGaP active layer, and a second conductivity type (AlxGa1xGa t-x
) A double heterostructure consisting of an I nP cladding layer,
A second conductivity type impurity is diffused from the surface of the second conductivity type cladding layer to provide a low refractive index region on the side surface near the striped active layer, thereby manufacturing a refractive index waveguide semiconductor laser. Then, the output angle in the horizontal direction with respect to the junction becomes larger than that of the conventional element. Furthermore, the astigmatism was 10 μm or less, which was an improvement.

Second, by growing the active layer at a growth temperature of around eao ~ 700°C, it is possible to increase the effective refractive index difference between the diffusion regions in the striped active layer, which reduces astigmatism. is as small as 1 to 2 μm, and it is now possible to obtain a larger horizontal output angle by -1.

[Brief explanation of the drawing]

1 is a cross-sectional view of a semiconductor laser according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a semiconductor laser according to a first embodiment of the present invention, and FIG. 3 is a manufacturing process of the device shown in FIG. 1. Cross-sectional view, FIG. 4 is a cross-sectional view of a conventional embodiment. 11...N base Ga 8 board, 13...
n is (AlxGa/xG''+-x)InP cladding layer,
14------pti(51xGa, -x) In
P cladding layer, 21-----n-type Ga-mutant flow blocking layer, 20...Zn diffusion layer. Name of agent: Patent attorney Shigetaka Awano and 1 other person20
-・-P! Joshukan diagram diagram (G

Claims (3)

[Claims] (1) A first conductivity type (Al_xGa_1_-_x)InP cladding layer (
0<x≦1), (Al_yGa_1_-_7)InP active layer (0≦y<x, z) and a second conductivity type (Al_zGa_1_-_2)In having striped convex portions.
having a P cladding layer (0<z≦1), from the surface of the second conductivity type cladding layer to the active layer excluding the active layer located directly below the convex portion and into the first conductivity type cladding layer; A semiconductor laser comprising a region in which a second conductivity type impurity is diffused. (2) A first conductivity type (Al_xGa_1_-_x) InP cladding layer (0
<x≦1), (Al_yGa_1_-_y)InP(0
≦y<1) active layer and second conductivity type (Al_zGa
_1_-_z) The first growth step of laminating a double heterostructure formed by forming an InP cladding layer (0<z≦1) and etching the second conductivity type cladding layer in a stripe shape to form convex portions. and a step of diffusing impurities of a second conductivity type from the surface of the second conductivity type cladding layer to the active layer excluding the active layer located directly below the convex portion and the first conductivity type cladding layer. . A method for manufacturing a semiconductor laser, comprising the step of growing a compound semiconductor lattice-matched to the substrate after the diffusion step. (3) Growth temperature from 630°C to 70°C using organometallic vapor phase epitaxy
(Al_yGa_1_-_y)InP in the range up to 0℃
3. The method of manufacturing a semiconductor laser according to claim 2, wherein an active layer (0≦y<1) is grown.