JPS62108591A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To grow a crystal on a semiconductor with an active surface twice or more by attaching a semiconductor thin-film with a stable surface onto the surface of a semiconductor with an unstable surface, using the thin-film as a protective film and substantially annihilating the protective film by utilizing the mutual diffusion of constituent elements by an impurity. CONSTITUTION:An N-GaAlAs clad layer 2, a GaAs/GaAlAs superlattice laser active layer 3, a P-GaAlAs clad layer 4, an undoped GaAs protective layer 5, an undoped GaAlAs layer 6 and an absorption layer 7 are grown on a substrate 1 in succession. A crystal is taken out of a growth device, and dry-etched selectively by a CO2F2 group gas, GaAs 7 is removed in a striped manner, GaAlAs 6 in a region 10 is removed by a mixed liquid of hydrofluoric acid and ammonium peroxide, and the whole is introduced into a growth chamber and second growth is conducted. A P-GaAlAs clad layer 8 using Zn as a dopant and a cap layer are grown, and heat treatment is performed under As pressure. The thin-film 5 corresponding to the region 10 is eliminated by a change into an impurity-induced mixed crystal of Zn.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] A crystal growth technique for easily obtaining a desired structure when a semiconductor laser has a structure such as transverse mode confinement;
Regarding process technology.

[Background of the invention]

As a method for easily controlling the transverse mode of a GaA Q As-based visible semiconductor laser, an nfiGaAs layer is attached on the p-type GaA Q As cladding layer, and only the laser active region is
A structure is known in which GaAs is removed and a p-type GaA Q As cladding layer is regrown.

However, this method does not work well with surface-active GaAΩAs.
Because it is exposed to air, the surface oxidizes and defects are likely to be introduced at the interface during regrowth.

In contrast, the crystal surface before starting regrowth is Ga
With A s, it is difficult to form an oxide film and a good interface can be obtained.
Spring Lecture Proceedings, page 131 Lecture number 30a-ZB-
7, on p-GaA 41 As with a thickness of 0.
The crystal was placed in a molecular beam epitaxy (MBE) apparatus with 1 to 0.2 μm of Ga As remaining.

By heating while applying As molecular beam, G a A
The p-GaA Q As cladding is exposed to the surface by thermally etching the s thin film in a high vacuum.
It has been reported that As re-grows thereon. However, this method requires ultra-high vacuum and cannot be used with OMVPE (organic metal vapor phase epitaxy), which is suitable for mass production.

[Purpose of the invention]

The purpose of the present invention is to develop a method using the OMVPE method that allows crystal growth to be performed more than once on a semiconductor with an active surface in order to create the internal structure necessary to provide a transverse mode confinement function to a semiconductor laser. give you the means to do so.

[Summary of the invention]

The present invention provides a method in which a semiconductor thin film with a stable surface is attached on a semiconductor surface with an unstable surface and used as a protective film, and then the protective film is substantially eliminated by utilizing interdiffusion of constituent elements caused by impurities. Invented and demonstrated.

[Embodiments of the invention]

The present invention will be explained in detail below.

nGaAs, n-Ga 0.4A A on substrate 1
o, aAs cladding layer 2, Ga As / Ga
o, sA no, aA s superlattice laser active layer 3
+ p-G ao, aA Mo, sAs cladding layer 4
．． Undoped G a As protective layer 5 thickness 100 people),
Undoped G ao, aA Q 0.7A s layer 6 (
thickness 0.2 pm), n-GaAs layer absorption layer 7 is OMVP
E! It grows sequentially by law. At this time, Mg was used as the p-type impurity of layer 4.

Take out the crystal from the growth apparatus, make a photoresist mask using the usual photolithography method, and add C0zFz.
Selective dry etching of the GaAs 7 is performed using a system gas to remove the GaAs in the upper part 10 of the portion that will become the active layer region of the laser in the form of a stripe with a width of 3 μm.゛Next, using a mixed solution of hydrofluoric acid and ammonium peroxide (1:6), Ga o, sA Q 0.7A s 6 in area 10
remove.

Immediately introduce it into the OMVPE growth chamber and perform the second growth.

p -G ao, a A Q with Zn as a dopant
o, e As cladding layer 8. Grow a p-GaAs cap layer. A cross section of the crystal at this stage is shown in FIG.

FIG. 3 shows the cross section of the laser after heat treatment at 850° C.lhr under As pressure. Ga corresponding to region 10
The As thin film 5 has disappeared due to impurity-induced mixed crystal formation of Zn.

Below, using normal semiconductor laser manufacturing, the p-side utility pole 12 is
After forming the n-side electrode 13, two rough edges were formed between the folds to produce a semiconductor laser. The oscillation threshold current value of the obtained semiconductor laser was 15 mA.

The output was 150mW. In the 10 crystals grown, the variation in threshold value between wafers was ±2%, indicating that this method is a crystal regeneration method with extremely good reproducibility.

〔Effect of the invention〕

The present invention provides a method for regrowing GaAΩAs on GaAQAs with good reproducibility using OMVPE, a crystal growth method suitable for mass production. With this method,
This makes it possible to triple the yield of crystal growth, and has the effect of significantly reducing costs, including simplifying the inspection process.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of crystals grown by the method of the present invention. l---n-Ga As substrate, 2-=n-
GaA Q As layer, 3... laser active layer, 4...
p-G a AΩAs, 5... undoped Ga
As, 6... Undoped Ga1lAs, 7---
n-GaAs, 8-p-GaA Q As, 9
-p-GaAs, 10...A region where the layer is removed by etching, 11...A region where the GaAs protective film has disappeared due to impurity-induced mixed crystal formation, 12...p-side electrode, 1
3...n-side electrode. 2nd mouth

Claims (1)

[Claims] 1. A hetero semiconductor thin film structure (2) with a stable surface is grown on a semiconductor (1) with an unstable surface, and then a semiconductor crystal is subjected to a predetermined treatment outside the growth chamber, Growing a semiconductor crystal (3) with a larger energy band gap than in (2) above, doping impurities into (3) in advance,
Alternatively, impurities added later by diffusion, ion implantation, etc. may cause spatial changes in the constituent elements in (2) and (3), or (1), (2), and (3). A method for manufacturing a semiconductor laser, characterized in that the bandgap described in (2) above is increased by forming a mixed crystal by substitution or exchange. 2. On a surface active and easily oxidized material such as the Ga_1_-_xAl_xAs cladding layer (0) of a semiconductor laser,
When performing crystal regrowth, a GaAs thin film (preferably,
(1) Ga_1_ whose thin film is 50-200 Å
−_xAl_xAs(0.1≦x≦1, preferably 0.
3≦x) After growing the layer (2) and the GaAs layer (3), the crystal growth is stopped and the layer (3) and the layer (2) are replaced with GaAs.
After removing only the layer (3) by selective etching of GaAlAs, the layer (3) is removed by selective etching of GaAlAs.
After removing only 2) to expose a clean GaAs surface, MBE
Ga_1_-_yAl_yAs (0.1≦y≦1) layer (0.1≦y≦1) doped with impurities by method or MOCVD method.
4) is grown in contact with the GaAs layer (1),
During growth or by heat treatment after growth, the layer (0),
Ga and Al in the layer (1) and the layer (4) undergo impurity-induced mixed crystallization, and the energy bandgap of the layer (1) increases, making it substantially unable to absorb laser light. A method of manufacturing a semiconductor laser, characterized in that: