JPH04154183A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a semiconductor laser at a twice made growth by installing current block structure comprising an n type AlGaInP layer and a P type AlGaInP layer which claps said n type AlGaInP layer wherein said semiconductor laser is provided with large differential quantum efficiency and small astigmatism. CONSTITUTION:An attempt is made to install a mesa-shaped double hetero structure comprising an n(Al0.5Ga0.5In0.5P clad layer 2, which clamps a Ga0.5In0.5P active layer 3 on an n type GaAs substrate 1 and has a smaller refraction factor, and a P type (Al0.5Ga0.4)0.5In0.5P clad layer 4. More specifically, a current block structure is installed wherein the structure comprises the layer 2 which has a larger band gap than the layer 3 and a smaller refraction factor than the clad layer and a layer 4 which clamps the layer 2 and has a larger band gap than the layer and a smaller refraction factor than the clad layer. This construction makes it possible to manufacture a semiconductor laser at a twice made growth wherein the semiconductor laser is a real refraction factor waveguide type in horizontal mode control structure having small astigmatism.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ApGaInP semiconductor laser that oscillates in a single mode.

C. Prior Art In recent years, an AlGaInP semiconductor laser device that oscillates in a single transverse mode and is formed by a vapor phase crystal growth method called metal organic pyrolysis method (hereinafter abbreviated as MOVPE method) has been developed as shown in FIG. structure has been reported in Electronics Letters (S. Kawata, H. Fujii, Kobayashi, A., Gomyo, L. Hino,
T, 5uzu-ki: EIectron, Lett, 2
3 (1987) 1327. ). The manufacturing process of this structure is shown in FIG. - In the second growth, n-type GaAs substrate 2
n-type on 1 (A no, s Ga O, 4) o5
Ino,s P cladding layer 22. Gao, s engineering no
5P active layer 23. p-type (A (lo, a Ga O
, 4) 0.5 I no, s P inner layer 24, p type Ga o, h I no, sP Etching stopper layer 25, p type (A f2 o, a Ga
o, +) o, s I n o, s P outer Clara F
Layer 26. p-type G a o, s I n 0. An SP buffer layer 27 and a p-type GaAs cap layer 28 are sequentially formed. A 5iCh mask 31 in the form of a stripe with a width of 7 μm is formed on the wafer thus grown by photolithography (see FIG. 4 (a). Next, this SiO2 mask 31
pffGaAs was etched using a phosphoric acid-based etching solution.
A cap layer 28 is formed on the mesa (see Fig. 4).
b)). Next, p-type Ga
The portion up to the upper interface of the InP etching stopper layer 25 is etched into a mesa shape (FIG. 4(C)). Then, the p-type GaAs cap layer 28 is side-etched to a width of 3 μm using a phosphoric acid-based etching solution (FIG. 4(d)).
. Then, with the 5iOr mask still on, a second growth is performed and the etched area is embedded with an n-type GaAs blower 2 layer 29 (FIG. 4(e)). Next, S i O
2 masks are removed, and a third grown chilled GaAs contact layer 30 is grown so that an electrode can be formed on the p-type gold surface (FIG. 4(r)).

With this structure, current is blocked by the n-type GaAs layer 29 and is injected only into the mesa stripe portion. Further, the transverse mode can be sufficiently controlled by the difference in refractive index between the current block structure and the mesa structure.

As described above, with this manufacturing method, a refractive index guided semiconductor laser can be manufactured by growing three times.

[Problems to be Solved by the Invention] In the structure shown in FIG. 3, the band gap of the n-type GaAs layer used as the current blocking layer is smaller than that of the active layer, so light is absorbed by the blocking layer. There is a problem that external differential quantum efficiency decreases due to increased loss within the resonator, and astigmatism increases due to wave front delay at the interface between the n-type flock layer and the mesa. Furthermore, the method for manufacturing a semiconductor laser with a conventional structure requires a total of three growth cycles, requires the formation of an etching stopper layer, and requires two types of etchants, making the process complicated.

The purpose of the present invention is to solve the above-mentioned problem of absorption by the current blocking layer, and to provide a real refractive index waveguide type and current confinement type semiconductor laser having a transverse mode control structure with high external differential quantum efficiency and small astigmatism. The goal is to manufacture and provide products by growing them twice.

[Means to solve the problem]

The semiconductor laser of the present invention has GaI on an n-type GaAs substrate.
nP or AI! It has a mesa-like tuffle heterostructure consisting of an active layer made of GaInP or a quantum well structure thereof, and an AρGaInP cladding layer with a refractive index smaller than that of the active layer sandwiching this active layer. On both sides are n-type A, which has a larger band gap than the active layer and a smaller refractive index than the cladding layer, &GaInP layers, and p-type layers, which have a larger band gap than the active layer and a smaller refractive index than the cladding layer, sandwiching this n-type AfflGaInP layer.
It has a current blocking structure consisting of a type AρGaInP layer, and is characterized by having a P-type Af2GaInP layer on the side surface of the mesa, which has a larger band gap than the active layer and a smaller refractive index than the cladding layer.

In the method for manufacturing a semiconductor laser of the present invention, the surface is (OO1)
On a semiconductor crystal substrate with a plane orientation, n-type Affl Ga I
nP cladding layer, undoped GaInP or Aj
A step of sequentially growing an active layer consisting of 7GaInP or a quantum well structure thereof, and a p-type Aj2GaInP cladding layer in a vapor phase, and etching the grown layer until it reaches the substrate to form an I-shaped layer with a (111) side surface. Ushimail eggplant T
A p-type AρInP layer, an n-type AlInP layer, and
p-type AlInP layer, p-type GaInP buffer layer, p-type G
The structure includes at least a process of sequential vapor phase growth of an aAs contact layer, and utilizes the fact that the Zn diffusion rate is different on the (OO1) plane, which is the substrate orientation, and on the (111) plane, which is the mesa side surface. , among the n-type semiconductor layers grown simultaneously on the (001) plane and the (111) plane, the (111
) is a manufacturing method characterized by converting only the n-type semiconductor layer grown on the surface to p-type.

[Effect]

According to the structure of the present invention, n-type AlGaInP on both sides of the mesa
layer and p-type AρGaIn sandwiching this n-type A6GaInP layer.
The current blocking structure consisting of the P layer has a larger band gap than the active layer and cannot absorb light from the active layer, so it is possible to reduce light loss and to reduce astigmatism.

In the method for manufacturing a semiconductor laser of the present invention, an n-type AρGaInP layer having a hand cap larger than the active layer and a lower refractive index than the cladding layer, and an n-type AρGaInP layer sandwiching this n-type AρGaInP layer having a larger band gap than the active layer and a refraction lower than the cladding layer are used. A current flock structure consisting of a p-type AρQaInP layer with a small ratio is grown on both sides of the mesa and on the side surface of the mesa, and when growing a p-type semiconductor layer on this current flock structure (
The diffusion of Zn on the (001) plane
The p-type Al on both sides of the mesa is
n-type A RG aInP layer sandwiched between GaInP layers
p-type A on the mesa side without converting to type AρGaInP layer.
Since only the n-type AnGaInP layer sandwiched between the lGaInP layers is converted into a p-type AlGaInP layer, a current confinement type and real refractive index guided type semiconductor laser can be manufactured with two growths.

〔Example〕

Embodiments of the present invention will be described using the drawings. FIG. 1 is a sectional view of a laser diode showing an embodiment of the semiconductor laser of the present invention, and FIG. 2 is a process diagram thereof. First, the n-type GaAs substrate 1 (
Si-doped, n=2X 10" n-type (A
40.6 G a o, +) i5 I n o,s
P cladding layer 2 (n=5 x 1017cm-3:
thickness 1 μm), Ga o, s I no, sP active layer 3 (undoped; thickness 0.1 μm), p type (A j2
o, e G a Q, 4) 0.5 I n o, s
A P cladding layer 4 (thickness 11 μm) was sequentially formed (
Figure 2(a)). The growth conditions were a temperature of 660°C, a pressure cuff of 0°Torr, and a V1m ratio of 150. The total flow rate L5 (27 Mm) of the carrier gas (H2) was used.The raw materials were trimethylindium (TMI: (CH=)3I n), triethyl gallium (TEG: (02H5)3Ga)
, trimethylaluminum (TMA: (CH3)
3Aρ), arsine (AH3), phosphine (PH3
), n-type dopant: disilane (SizH-), p-type dopant: dimethyl zinc (DMZn: (CH,)z
Zn) was used. The thus grown wafer was coated with SiO on a 7 μm wide stripe by photolithography.
2 masks 11 were formed (FIG. 2(a)). Subsequently, the mesa was etched up to the upper interface of the n-type cladding layer using a hydrochloric acid-based etching solution (FIG. 2(b)). At this time, the mesa side surface becomes a (111) plane. Next, after removing the 5if2 mask, a second growth is performed by low pressure MOVPE,
p-type Al2a, sIn. 5P cladding layer 5 (thickness 11μ
m) and n-type Auo, sI no, sP cladding layer 6 (
thickness 11 μm) and p-type A 12 o, s I n 0
．． Current block structure consisting of 5P cladding layer 7 (thickness 11 μm) and p-type Gao, sIn. A 5P buffer layer 8 (thickness: 0.1 μm) and a p-type GaAs contact layer 9 (thickness: 12 μm) were formed (FIG. 2(C)).

(d)). Here, p-type A II o, s I no,
s P cladding layer 7 and p-type Ga o, s I n 0
．． P buffer layer 8 and p-type GaAs contact layer 9
Dimethyl zinc is used as a dopant when forming Zn, but the diffusion of Zn is faster on the (111) plane, which is the mesa side surface, than on the (001) plane, which is the substrate orientation. The portion of the cladding layer 6 on the side surface of the mesa is p-type Aρo, s I n o, s
Zn is diffused from the P Clara F layer 7 and the p-type GaO, 5InosP buffer layer 8 and the p-type GaAs contact layer 9 to form the p-type Aρ. 5Ino, becomes the sP layer 10 (second
Figure (d)). Finally, both p and n electrodes (not shown) are connected to p-type GaAs contact layers 8. n-type Ga
It was formed on an As substrate, cleaved to a cavity length of 300 μm, and separated into individual chips.

In the above manufacturing process, the mesa width was 4 μm at the top and 10 μm at the bottom. When the external differential quantum efficiency of the semiconductor laser of the present invention thus obtained was compared with that of a laser with a conventional structure having a mesa width of 4 μm, it was found that the laser with a conventional structure had an external differential quantum efficiency of 0.43. The external differential quantum efficiency of the laser improved to 0.50, and the threshold current at 25° C. decreased from 45 mA to 35 mA. Furthermore, astigmatism has been reduced from 7 μm to 4 Pmu below. In the embodiments described above, the active layers are G a o and s I n. 5P
, the cladding layer is (A n O,6G a O,4) 0
．． 5 I no, s P, but the active layer composition should be a composition, material, or quantum well that satisfies the oscillation wavelength requirements for the laser to be fabricated, and the cladding layer composition should be the one that meets the optical and Composition that allows for sufficient carrier confinement.

All you have to do is choose the material. Also, depending on the characteristics required of the laser, it is possible to use an SCH structure. Furthermore, p-type A i O,5■n0. which forms a current flock structure. sp layer 5. n-type Af c5 I n 0.5P layer6. p-type A,
The L, +Ino5P layer 7 has a different composition, except that it has a larger non-ant cap than the active layer and a smaller refractive index than the crat layer.

It may be a material.

[Effects of the invention] As described above, according to the present invention, the external differential quantum efficiency can be increased,
A semiconductor laser with small astigmatism can be manufactured using a simple method.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2(a) -
(d) is a diagram showing the manufacturing process of the semiconductor laser of the present invention, FIG. 3 is a cross-sectional view showing an example of a conventional semiconductor laser, and FIG.
a) to () are diagrams showing the manufacturing process of a conventional semiconductor laser. In the figure, 1 is an n-type GaAs substrate, 2 is an n-type (A
no, s G a O, 4) 0.5 I no
5P cladding layer, 3 is Gao5Ino, sP active layer, 4
is p-type (A 4 o6G a 0.4) 0.11nc
5P cladding layer, 5 is p-type A 120.5 I na
, s P layer, 6 is n-type A (! 0.5 I no,
sP layer, 7 is p type A (2o5Ins, sP layer, 8 is p
type G a o, s I n osP buffer layer, 9 is p type G a AS ) contact layer, 10 is p type A, j
l'o, 5 Inc, sP layer, 11 is a SiO2 film. Agent Patent Attorney Shinman Uchihara

Claims (1)

[Claims] 1. GaInP or AlG on an n-type GaAs substrate
An active layer consisting of aInP or a quantum well structure thereof, and an Al layer with a smaller refractive index than the active layer sandwiching this active layer.
It has a mesa-like double heterostructure consisting of a GaInP cladding layer, and this n-type AlGaInP layer is sandwiched between an n-type AlGaInP layer having a larger band gap than the active layer and a smaller refractive index than the cladding layer on the top and both sides of the mesa. ,
It has a current blocking structure consisting of a p-type AlGaInP layer with a larger bandgap than the active layer and a smaller refractive index than the cladding layer, and a p-type AlGaInP layer with a larger bandgap than the active layer and a smaller refractive index than the cladding layer on the side surface of the mesa.
A semiconductor laser characterized by having a P layer. 2. On a semiconductor crystal substrate with a (001) surface orientation, n
A process of sequentially vapor-phase growing a type AlGaInP cladding layer, an active layer made of undoped GaInP or AlGaInP or a quantum well structure thereof, and a p-type AlGaInP cladding layer, and etching the grown layer until it reaches the substrate so that the side surfaces are (111). A step of forming a mesa stripe on the surface, and covering the mesa stripe, using Zn as the dopant of each p-type layer, forming a p-type AlInP layer, an n-type AlInP layer, a p-type AlInP layer, a p-type GaInP buffer layer, and a p-type GaAs contact. 1. A method for manufacturing a semiconductor laser, comprising at least the step of sequentially growing layers in a vapor phase.