JPH01120084A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To easily manufacture a short-wavelength laser whose unity in transverse mode is excellent by a method wherein, after a first clad layer and an antioxidation layer have been grown on a U-shaped groove by an LPE method so as to make the surface flat, a double heterostructure including a second clad layer is grown again on them. CONSTITUTION:The following two are formed one after another on a GaAs substrate 1 of a first conductivity type having at least a groove 2 as a first crystal growth process: a first clad layer 3 composed of an AlxGa1-xAs layer of the first conductivity type which fills the groove 2 by a liquid growth method, which has a flat upper face, whose forbidden band width is larger than that of an active layer and whose refractive index is small; a GazIn1-zP antioxidation layer 4 (z-0.5) of the first conductivity type on the first clad layer 3. Then, at least a second clad layer 5 of the first conductivity type, an active layer 6 and a clad layer 7 of a second conductivity type are formed one after another on said GazIn1-zP antioxidation layer 4 as a second crystal growth process. Said second crystal growth process is executed by using a crystal growth method in a thermal non-equilibrium state, e.g. a metal organic vapor growth method, a molecular beam growth method or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a single transverse mode short wavelength semiconductor laser that can be used for optical communication of information, optical erasing, recording, reproducing, etc.

2. Description of the Related Art In recent years, 0.8μr4i with a structure as shown in FIG.
AIGaAs semiconductor lasers have been put into practical use. On the other hand, in order to aim for even higher performance, A7GaIn
0.871 m to 0.7 m, represented by P-based semiconductor lasers and AIG a S-based quantum well semiconductor lasers.
There is a strong demand for 71m band short wavelength short wavelength semiconductor lasers.

Below, 0,871m with conventional transverse mode control shown in Figure 3.
A band jJ GaAs semiconductor laser will be explained.

1 is an n-GaAs substrate provided with grooves 2, 12 is an n-Al
yGa1. , As cladding layer, 13 is non-doped Al
y Ga 1-y As active layer (y'<y), 1
4 is a p-AlyGa1-yAs cladding layer, 8 is an n-GaAs cap layer, 9 is a Zn diffusion layer,
Reference numerals 10 and 11 are respectively "r P side electrodes. The above structure is formed by liquid phase epitaxy (hereinafter referred to as LPE method), and the upper surface of the n-AlyGa 1-, As 2-rad layer 12 is flattened. In this structure, the current flows only in the groove 12 due to the Zn diffusion layer 9, and the active layer on the groove 12 emits light. A part of the laser oscillated light leaks into the cladding layer. The light is absorbed outside the groove of the n-GaAs substrate 1, resulting in an effective refractive index difference in the lateral direction, and the light is confined (transverse mode control).

Problems to be Solved by the Invention However, even shorter wavelength semiconductor lasers such as AIG
When this structure is applied to an aInP semiconductor laser medium conductor laser or an aAs quantum well semiconductor laser, there are various constraints on crystal growth compared to other material systems.
It was difficult to form.

The former is difficult to form due to thermodynamic limitations, and the latter is difficult to form using the conventionally commonly used LPE method from the viewpoint of controllability of film thickness. Furthermore, metal organic vapor phase epitaxy (hereinafter referred to as MovPE method) and molecular beam growth method (hereinafter referred to as MBE method), which are growth methods under thermal non-equilibrium conditions, have drawbacks such as difficulty in trench-filling growth. , as is often done in the LPE method as shown in Figure 3, a groove is formed in the substrate, and a double heterostructure is stacked so that the groove is filled, and the effective light absorption by the substrate on both sides of the groove is achieved. It is difficult to apply this method to a type of semiconductor laser that forms a light guide.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and provide a method for manufacturing a short wavelength laser with excellent transverse mode unity.

Means for solving the problems The technical means of the present invention for solving the above problems is LP
A first aluminum cladding layer, gold, which has a larger forbidden band and a lower refractive index than the material that will become the active layer, is formed on the GaAs substrate, which has grooves formed in advance using the E method, and is flattened on its upper surface. Then, the A to G
Ga to prevent the a i -yA s layer from being oxidized
zI n 1-zP oxidation prevention layer (z -0,5) is formed, and then a second layer is formed by MOVPE or MBE.
A predetermined double heterostructure including a cladding layer is laminated. In this case, the first AlGaAs cladding layer completely confines light to the active layer by laminating at least the second cladding layer in the groove, and Ga
The thickness is chosen to be sufficient for the As substrate to act as a light absorption layer.

Function In the present invention, in order to control the transverse mode of a short wavelength semiconductor laser, the first A11xGa 1-xA is grown on the concave groove so that the surface is flat by the LPE method that allows trench-filling growth.
s G a 2 to prevent oxidation of the cladding layer and its surface
Step of growing In 1-zP layer and MOV on it
The structure is composed of a process of regrowing a double heterostructure including a second cladding layer by PE method or MBE method. Even if the crystallinity of the regrown interface and regrown layer is deteriorated, the crystallinity of the regrown interface and the regrown layer will not be impaired.Moreover, the cladding layer on the substrate side is sufficiently optically confined in the groove by the stacking of the first and second cladding layers. G a A s outside
By making the substrate work as a light absorption layer,
A transverse mode short wavelength laser can be realized.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic sectional view when the present invention is implemented, and FIG. 2 is a process diagram showing the main manufacturing process.

First, as shown in FIG. 2A, a groove 2 is formed on an n-GaAs substrate 1 by ordinary photolithography and chemical etching. The depth and width of the groove are each 1
, #m, 5 Itm. Next, as shown in FIG. 2B, nA was formed as the first cladding layer by LPE method
lo, 7 Ga o, 5A 8 layers3. nGao, sIno, sP4 as anti-oxidation layer
grow sequentially. At this time, n-Alo, 7Ga, As
Layer 3 has a flat surface, and its thickness is 1.2 at the groove 2 part.
71 m, 0.2 It m outside groove 2.

The thickness of the n-Gao, sIno, sP layer 4 is 50A.

Immediately after the first crystal growth step by LPE method, MO
n All as a second cladding layer following thermal cleaning for 10 minutes in a PH3 atmosphere by VPE
l], 2 G a o, ! , I no, 5P layer 5
．． Non-doped G ao, s I n o as active layer
, s P layer 6. Furthermore, as a cladding layer of the opposite conductivity type, p#
o, 2Gao, 3In. , 5P layer 7. An n-GaAs layer 8 is sequentially grown as a cap layer. At this time, the regrown interface is good and there is no problem with the crystallinity of the regrown layer.

The thickness of each layer is 0.171m, 0.171m
, 11trn, 1/1m.

Zinc (Zn) is selectively diffused onto this surface so that the Zn diffusion layer 9 reaches the p-Alo, 2Ga o, 3In 0.5'' layer 6. Next, the n-side electrode 1o and the p-side electrode 11 is applied, followed by cleavage mounting and packaging.

Active layer G ao,s I n formed by MOVPE method
o, s The forbidden band width of the P layer 6 is 1.85e, V,
The first A710.7 Ga cLsAs cladding layer 3 and the second Alo,2(ja O,3I no,s
Both of the forbidden band widths of the P cladding layer 5 are 2.1 eV or more, and sufficient light confinement is achieved at the above film thickness. The Ga(,,51n.,5P) oxidation preventing layer 4 is sufficiently thin and formed by the LPE method, has a forbidden band width of 1.9 eV, does not absorb light, and does not cause any problems in terms of characteristics.

In addition, in the above explanation, AlGa
Although the case of forming an InP-based double heterostructure has been described, it goes without saying that it may be applied to an A 73 Ga As-based structure or even an active layer having a quantum well structure.

Further, the present invention is applicable to cases in which layers of conductivity type opposite to those in the above embodiments are formed on a p-GaAs substrate, and in addition, GaAs
A current confinement layer of an opposite conductivity type may be provided on the substrate and penetrated by a groove portion.

Effects of the Invention As described above, according to the present invention, a single transverse mode short wavelength semiconductor laser utilizing a concave groove can be easily obtained, and the practical effects are excellent.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a semiconductor laser according to an embodiment of the present invention, Fig. 2 is a cross-sectional view showing the entire manufacturing process of the semiconductor laser according to the embodiment in order, and Fig. 3 is a conventional semiconductor laser with controlled transverse mode. FIG. 1...-n-GaAs substrate, 2...-concave groove, 3...-first n-All, Ga,
-xAs layer cladding layer, 4...mark/n Gao, sIn
. , 5 anti-fouling layer, 6... second n-A10.
2G"0.3"0.5P cladding layer, 6... Self-undoped Ga o, s I no, s P active layer, 7
・・・・・・p-Al1 o, 2Ga O,s I
no, s P cladding layer, 8...n-G
a A s camp layer, 9...Zn diffusion layer, 1
o...n side electrode, 11...p side electrode,
12...n-AlyGa1-yAAl rad layer, 13...Non-doped AlyG a 1
Bow A s active layer, 14...p-AlGalGa
Name of Yatsuclad: Patent attorney Toshio Nakao and 1 other person/
---n -Q-a-As basic talent? -Concave shit 3-11 / Q n-AJlty7Ga-o3As
Cladding layer 4- 几-rao, slru05β oxidation stop layer S
-'@2n--Al6.2 (7a, a, 31n
nsβ Craft 16---Nondove CrcLo, s
L? La, sF'/Ancient, Scrap 7 --- F-A1. o
, z (rra31fLa, sβcrat fake β'-n-
Qa-As 1,000-tap layer 9--27 diffusion 1/-= n-craAs substrate 2-11 groove 3--- 1st ty> rt-ALo, 7(:ra,
o, aha S7... throat eyebrow 4-几-shin σ51xθ5F oxidation bodhi counterfeit s-12/1yt-hough 0.2Qa-o, 3ko, sP
Clothed counterfeit 6- Non-dope Cta-o,s IfLo
, sP 5tsa layer/2---louver Ly(tαt-y
As cladding layer 13--Non-doped ALy'-G Cobblestone Birch 1/4---P-AJ-7cra-t-IAs
7 Rad 1 Figure 3

Claims (2)

[Claims] (1) A first conductivity type GaAs substrate having at least a groove, which fills the groove by a liquid phase growth method and has a flat upper surface, and which has a larger forbidden band width and a lower refractive index than the active layer. A first cladding layer made of an Al_xGa_1_-_xAs layer, and a first conductivity type Ga_zIn_1_-_zP anti-oxidation layer (z~0.
5) a first crystal growth step of sequentially forming the Ga_
A method for manufacturing a semiconductor laser, comprising a second crystal growth step of sequentially forming at least a second cladding layer of a first conductivity type, an active layer, and a cladding layer of a second conductivity type on a zIn_1_-_zP oxidation prevention layer. (2) The method for manufacturing a semiconductor laser according to claim 1, wherein the second crystal growth step is formed by a crystal growth method in a thermal non-equilibrium state such as a metal organic vapor phase epitaxy method or a molecular beam growth method. .