JPH01202880A - Double hetero junction type semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce lattice mismatching of a p-clad layer and to make it possible to control both of p- and n-clad layers to have lattice mismatching coefficients within + or -0.1%, by deviating the lattice mismatching coefficient of the n-clad layer to the plus side when forming a double hetero structure. CONSTITUTION:In a double hetero junction type semiconductor laser device formed on a GaAs substrate 10 which is provided with an active layer 12 between an n-type and p-type In1-y(Ga1-xAlx)yP(0<=x<=1, 0<=y<=1) clad layers 11, 13, the ratio a/a0 of the lattice constant (a) of the n-type clad layer 11 in the vertical direction of the substrate 10 and the lattice constant a0 of the GaAs substrate 10 is set at 1.0005<=a/a0<=1.001. By forming the lattice mismatching coefficient of the n-type In1-y(Ga1-xAlx)xP clad layer 11 deviated to more than +0.05% in this way, deviation of about 0.1-0.15% to the minus side developed by Zn doping in the growth of the p-clad layer 13 is compensated. The lattice mismatching coefficient can be thereby controlled within + or -0.1% for both of p- and n-quantity clad layers.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention relates to In (GaAJ)Pl-y
The present invention relates to a double heterojunction semiconductor laser device using a 1-x x y mixed crystal as a cladding layer.

(Prior art) In(GaAIl)P mixed crystal is 1-y
Since it has the largest direct transition bandgap among the l-X x y ■-v group compound semiconductors, it is attracting attention as a material for short-wavelength light-emitting devices. Recently, visible semiconductor lasers based on MOCVD (metal organic pyrolysis vapor deposition) have been reported.

An example is an internal narrow cavity type laser as shown in FIG. In the figure, (10) is an n-GaAs substrate, (11) is an n-GaAs substrate, and (11) is an n-GaAs substrate.
-In (Ga AJ!) Pcra 0.5 0.5 0. ．． 5. 0.5 Tsudo W(S
T-doping: 5 x 1017am-j, 1.0μm)
.

(12) is an InGaP active silicon layer (7:/F-
(13) is P-1n
(G ao, 5O05 AJ!) P clad 1i (Zn doped: 5
0.5 0.5 x 10 cIll, 1.0 μm), (
14) is P-In, 50a P cap layer (Zn doped nia x 10170.5 cm-3,0,05am), (15) is n-Ga
As current narrowness (St doping: 2 X 1 G 18
cm-3, 1, 0 μm).

(16) is a P-GaAs contact layer (Zn doped: 3
X 1 G ”an-3,3,0um) , (
17>(1g) is an ohmic electrode.

When producing a heterostructure using such a multicomponent mixed crystal, lattice matching between the substrate crystal and the epitaxial layer is important. In this case, GaAs and 1 nGaP, InGaAJP
lattice matching is required.

Lattice constant of GaAs substrate: 1 n l− epitaxially grown and strained on ao and GaAs substrates.

(Ga1-x Aix)y The deviation between the lattice constant: a in the direction perpendicular to the substrate of P is the lattice mismatch rate: Δa/aO, Δa/ao = [(a-ao)/ao]
If defined as
It is necessary to control within

When forming the above structure using the MOCVD method, In
Regarding the growth of the GaXP layer, hetero-growth with good lattice matching is possible by supplying a raw material gas whose flow rate is controlled to have a gas phase composition that is lattice-matched to Ga-x As (X40.5). be. The gas flow conditions at this time can be determined, for example, as follows. When the supply amount of Ga (gallium) is changed while keeping the supply amount of P (phosphorus) and fn (indium) constant,
Ga supply amount, that is, gas phase composition Xg and lattice mismatch rate Δa/
The relationship of aQ is as shown in FIG. In this figure Δa /
A gas phase composition XgO in which a O is 0% can be obtained. 1-2 of In(GaAl)yP
In the case of 1-x x , the flow rate conditions for lattice matching are similarly determined.

However, the X of the double hetero wafer produced in this way
What if we look at the line rocking curve? The peak of the strongest GaAs substrate, which shows the shape as shown in the i6 diagram,
There is a peak of the n-cladding layer almost overlapping with this right hem part, and a peak of the p-cladding layer is separated to the small angle side. From this result, the lattice mismatch rate Δa/a of each cladding layer
When o was calculated, it was +0.01% for n-cladding and -0.11% for p-cladding. This is a p-type double heterostructure.

Further investigation into the phenomenon of different lattice mismatch rates in the n-type cladding layer revealed that the lattice mismatch rate of impurity doping (Ga l/lx'I yP shifts to the negative side, that is, p-In (Ga1 -y, 1-
It was found that the lattice constant of x AI2x)yP tends to be smaller than that of undoped or n-doped.

The lattice mismatch shift due to Zn doping is 1x101
Approximately 0.1 to 0.15 to the negative side with doping of about 8
%Met.

As mentioned above, In (Ga A, g )
In the Pl-y l-x double heterojunction laser, the lattice constant changes due to impurity doping, and even if one of the pun clads is matched with a lattice mismatch rate of 0%, the other is mismatched. Considering crystal growth and variations within the wafer, the maximum is 0.
．． There is a possibility of deviation of 2% or more. The lattice mismatch rate causes crystal defects such as misfit dislocations to occur. Also, GaA
It is conceivable that a large lattice mismatch on one side of the active layer that is lattice matched to the s-substrate causes stress to be applied to the active layer, causing deterioration of characteristics.

(Problems to be Solved by the Invention) As described above, in a double heterojunction laser in which In (Qa t-21-x Al or P) is used as a cladding layer, the p-cladding layer is There was a problem in that the lattice constant of the cladding layer changed, and even if lattice matching was achieved in one cladding layer, the lattice matching would be mismatched in the other.

The present invention provides a double heterojunction laser in which the lattice mismatch caused by impurity doping is improved. - [Structure of the invention] (Means for solving the problem) The gist of this invention is that 'Zn-doped p-I
n (Ga 1-2 1-x ”, x)V P cladding layer has n-doped or undoped In
(Ga ty 1-31 AJx) By paying attention to the fact that the lattice mismatch rate of the p-cladding layer becomes smaller with respect to P, the lattice mismatch of the p-cladding layer can be reduced by a simple method of shifting the lattice mismatch rate of the n-cladding layer to the positive side in advance. It reduces alignment.

(Function) When forming a double heterostructure by MOCVD method,
n-type In (Ga AJ) PL-y
1-x x x By forming the cladding layer with the lattice mismatch rate shifted by +0.05% or more, the lattice mismatch rate caused by Zn doping during growth of the p-clad layer can be reduced by 0.1 to 0.1.
Compensates for a deviation of about 5% to the negative side. As a result, even if one cladding layer is lattice matched, the other cladding layer is lattice matched.
A lattice mismatch of about 1% or more than 0.2% depending on variations in crystal growth can now be controlled to within +0.15 for both the p and n cladding layers.

(Example) Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a process for manufacturing a semiconductor laser according to an embodiment of the present invention.

This laser is manufactured as follows.

First, an n-GaAs substrate 10 (Si doped: 2×10'
18cII+″″3) using the M OCV D method.
-In (Ga A4) P cladding layer 0.5 0.3 0.7 0.511 (S
t-doping: 5 X 10'cm-3) 1.0
μm.

Undoped InGaP active layer 12 (0,
10,50,5 μm), p+InO+5
0.3 AID,? ) o, 5 (Ga P cladding layer 13 (Zn doped: 5 x 10'c
m-3) GaP cap layer 1.0 μm 1p-”0.5 0.514 (Zn doped Nia X 10′ cm-3) 0.05 μm.

n-GaAs current confinement layer 15 (Si doped: 2 x 1
018 cm-”) Continuously form Lou m (
(Fig. 1(a)), at this time I no,s (G
a t, aAJ! ) P is Ino, from the relationship between the gas phase composition
5(Qa, 3Ax) Lattice mismatch rate Δa of P
It is carried out under conditions such that the gas phase composition is between Xgl and Xg2 such that O,70,5/aO is in the range of +0.05 to +0.1%.

Next, in a general photolithography process, n-GaAs is
The current confinement Jiffl 15 is removed in a stripe shape with a width of 7 μm (FIG. 1(b)). Then, a p-QaAs contact layer is grown again by MOCVD. The first crystal growth condition until the formation of the current confinement layer is a susceptor temperature of Tg-8.
00°C, growth pressure Pg-257orr + total flow rate F = 10
4/m1n, V/I [I-500+ p-G a
A8: The second crystal growth condition for tact growth is Tg-700°C.

Pg-50Torr, F-104! /win, V/I
II-300.

When we examined the X-ray diffraction spectrum of the fabricated double hetero wafer, we obtained a profile as shown in Figure 3. The lattice mismatch rate was +0.055% for the n-cladding layer and -0.06% for the p-cladding layer. Met.

A laser device prototyped from this wafer showed good characteristics up to the periphery of the wafer, and no noticeable deterioration was observed in screening tests. Even after several growths under different conditions, both claddings were controlled to a lattice mismatch ratio within +0.15.

[Effects of the Invention] According to the present invention, by shifting the lattice mismatch rate of the n-clad layer to the positive side when forming a double heterostructure, the lattice mismatch of the p-clad layer can be reduced, and the lattice mismatch of the p-clad layer can be reduced. , n' It becomes possible to obtain a double heterojunction laser in which both cladding layers are controlled to have a lattice mismatch ratio of within +0 and 196, and a high-density short wavelength laser can be manufactured with high yield.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the manufacturing process of a semiconductor laser for explaining the present invention in detail, and FIG.
J! ) Gas phase composition in P and 0.3 0
．． 7 0.5 A diagram showing the relationship between lattice mismatch ratios, FIG. 3 is a diagram showing the X-ray rocking curve of the double heteronymous/% fabricated in the example of the present invention, and FIG. A cross-sectional view, FIG. 5 is a diagram showing the 0.5 relationship between the gas phase composition and the lattice mismatch rate in Ino4GaP, and FIG. 6 is a diagram showing the X-ray rocking curve of a conventional double heterojunction laser. It is. 10”・n-GaAs substrate (Si doped: 2
x1018cm-3), (Ga AJ) 11°"'' nO,50,30,70,5P cladding layer (st dope: 5 x 1017cm-3)
, Ga P active layer, 12 ... undoped InO, 50,5 (Ga
AJ2) 13°”p-”0.5 0.3 0.7
0.5P cladding layer (Zn doped: 5 x 10'
an-3), 1 4 ... p -1n G a
o, 5 0.5P cap layer (Zn doped: 7 X 1017 cm-3), 15
...n-G a As current confinement layer (Si doped: 2
X 10 "am-3), 16...p-GaAs contact layer 17.18... Ohmic electrode.

Claims (2)

[Claims] (1) The active layer is n-type and p-type In_1_-_y(Ga_
1_-_xAl_x)_yP(0≦x≦1, 0≦y≦1
) In a double heterojunction semiconductor laser device formed on a GaAs substrate sandwiched between cladding layers, the lattice constant of the n-type cladding layer in the direction perpendicular to the substrate: a
A double heterojunction type semiconductor laser device characterized in that the ratio a/a_0 of the lattice constant of the GaAs substrate and the lattice constant a_0 of the GaAs substrate is 1.0005≦a/a_0≦1.001. (2) The double heterojunction semiconductor laser device according to claim 1, wherein the acceptor impurity of the p-type cladding layer is Zn.