JPH04311079A - Manufacture of surface-emissioin semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a surface level so as to easily obtain a surface-emission semiconductor laser good enough in characteristics by a method wherein an active layer is etched with zinc compound-containing etching gas, and an etching mask is formed of insulator or metal. CONSTITUTION:An N-type GaAs buffer layer 103, a distributed reflection type multilayered film mirror 104, an N-type clad layer 105, a P-type GaAs active layer 106, a P-type clad layer 107, and a P-type contact layer 108 are epitaxially grown in succession on an N-type GaAs substrate 102. An SiO2 layer is formed on the surface through a hot CVD method, which is formed into a cylindrical SiO2 112 through photo-patterning. A cylindrical light emitting part is formed through etching. At this point, the etching gas contains dimethylzinc or diethylzinc or organic zinc compound, and the etching mask is formed of photoresist, silicon oxide, silicon nitride, molybdenum, or nickel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser that emits laser light in a direction perpendicular to a substrate.

0002

2. Description of the Related Art Conventionally, the following methods have been known for manufacturing surface-emitting semiconductor lasers.

First, n-type AlGaAs was applied to an n-type GaAs substrate.
/AlAs multilayer reflective film, n-type AlGaAs cladding layer,
p-type GaAs active layer, p-type AlGaAs cladding layer, p-type GaAs active layer, p-type AlGaAs cladding layer,
Epitaxially grow a type AlGaAs cap layer.

Next, a circular pattern with a radius of about 5 μm is formed using photoresist.

[0005] And reactive ion beam etching method (
After etching is performed until the n-type GaAs substrate (hereinafter abbreviated as RIBE method) is reached, it is filled with semi-insulating ZnSSe.

[0006] This is a method for manufacturing a surface emitting semiconductor laser through several steps.

[0007]

[Problems to be Solved by the Invention] However, in this conventional manufacturing method, ZnS is buried after etching.
A large number of interface states are generated at the interface between the Se layer and the GaAs active layer, making it extremely difficult to obtain a sufficient device.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve these conventional problems, prevent the generation of interface states, and easily obtain a device with sufficient characteristics.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the method for manufacturing a surface emitting semiconductor laser of the present invention has the following features.

A substrate-side reflector made of a III-V compound semiconductor is formed on a substrate made of a semiconductor or a dielectric in a direction perpendicular to the main surface of the substrate, and a part or the whole of the reflector made of a III-V compound semiconductor is etched. In a method for manufacturing a surface emitting semiconductor laser having a resonator having an active layer processed into a columnar shape by gas etching using a mask and a surface side reflector made of a semiconductor, dielectric, or metal, gas etching of the active layer is performed. Sometimes an etching gas containing dimethylzinc, diethylzinc, or an organic zinc compound is used, and the material of the etching mask is an insulator such as photoresist, silicon oxide, or silicon nitride, or a metal such as molybdenum or nickel. .

[0011]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

As an example of the present invention, a manufacturing method using dimethylzinc as the etching gas will be described.

FIG. 1 is a cross-sectional view of the manufacturing process for explaining the manufacturing process using the method of manufacturing a surface emitting semiconductor laser of the present invention.

FIG. 2 is a perspective view showing a cross section of a surface emitting semiconductor laser light emitting section manufactured by the method of manufacturing a surface emitting semiconductor laser according to the present invention.

Next, the manufacturing process will be explained.

(102) n-type GaAs substrate, (103
) n-type GaAs buffer layer, n-type AlAs layer and n-type Al
0.1 Ga0.9 As layer, 30 pairs (1
04) Distributed reflection multilayer mirror, (105) n-type Al0
．． 1 Ga0.9 As cladding layer, (106) p-type G
aAs active layer, (107) p-type Al0.4 Ga0.6
As cladding layer, (108) p-type Al0.1 Ga0
．． A 9 As contact layer is sequentially grown epitaxially by metal organic vapor phase epitaxy (hereinafter referred to as OMVPE) (FIG. 1(a)). The growth temperature at this time was 700°C, the growth pressure was 150 Torr, TMG (trimethyl gallium) and TMA (trimethyl aluminum) as group III raw materials, AsH3 (arsine) as group V raw materials, and H2 as n-type dopant.
Se (hydrogen selenide), DEZn (
diethyl zinc) was used.

After growth, SiO2 is deposited on the surface by thermal CVD method.
After forming the layer, a (112) SiO2 pattern with a diameter of 5 μm is created by a normal photopatterning process.

Next, a cylindrical light emitting section is created by gas etching.

The following etching conditions were used.

[0020] Dimethylzinc 100μmol
/min Hydrogen 1000 SCCM Substrate temperature 550° C. Etching chamber pressure 6000 Pa Under the above conditions, etching is performed up to the (102) n-type GaAs substrate.

[0021] Next, (109)ZnS was obtained by OMVPE method.
A 0.06Se0.94 layer is selectively buried and grown.

The following growth conditions were used.

[0023] Dimethyl selenium 140 μmol/
min dimethyl sulfur 70 μmol/min dimethyl zinc 100 μmol/min hydrogen
1 LSM substrate temperature 550℃ Etching chamber pressure 1
×10 4 Pa This selective buried growth was performed in a chamber where gas etching was performed without exposing it to the outside air.

After this selective implantation growth, it is taken out from the chamber.

Furthermore, 4 pairs of SiO2/α-
A (111) dielectric multilayer film made of Si (amorphous silicon) is formed by electron beam evaporation and removed by wet etching, leaving a region slightly smaller than the diameter of the light emitting part (FIG. 1(d)). The reflectance of the dielectric multilayer film at a wavelength of 870 nm is 94%.

After that, a (110) p-type ohmic electrode is deposited on the surface other than the (111) dielectric multilayer film, and then (
101) N-type ohmic electrode was evaporated and 4
Alloying at 20°C completes the surface emitting semiconductor laser (
Figure 1(e)).

The surface-emitting semiconductor laser manufactured by the manufacturing method of this example is different from conventional III-V compound semiconductors and II-V compound semiconductors.
-The generation of a large number of interface states that would otherwise be unavoidable at the interface with the Group VI compound semiconductor can be significantly suppressed.

[0028] Therefore, optical loss and carrier injection loss caused by interface states can be suppressed.

Further, FIG. 3 is a diagram showing the relationship between the driving current and the oscillation light output of a surface emitting semiconductor laser manufactured by the method for manufacturing a surface emitting semiconductor laser of the present invention. Continuous oscillation was achieved at room temperature, and an extremely low threshold value of 1 mA was obtained. The external differential quantum efficiency is also high, and suppression of optical loss caused by interface states and carrier injection loss contributes to improved laser characteristics.

Furthermore, since the reliability was greatly improved by suppressing the interface states, sufficient reliability could be ensured even under the temperature condition of 60°C.

Note that in the embodiments described so far, GaAs is used for the active layer. Of course, this is Alx in the active layer.
Sufficient effects can also be obtained when Ga1-x As (0≦X≦0.4) is used.

It is particularly effective in suppressing interface states and interface defects when the Al mixed crystal ratio X is large.

[0033] Also, other III-V compound semiconductors,
In particular, when a compound semiconductor used for optical communication such as InGaAsP is used, the monochromaticity of the surface emitting semiconductor laser also works effectively, making it compatible with advanced optical communication technology.

Of course, effective results can also be obtained using other III-V compound semiconductors.

[0035] Furthermore, the buried layer is also made of ZnS0.06Se0
．． Suitable I, not limited to 94 mixed crystals and ZnS-ZnSe superlattices.
I-VI group compound semiconductors such as ZnSe, ZnS, and Cd
A similar effect can be obtained by selecting Te, its mixed crystal, or a superlattice made of these materials as the buried layer.

Further, the substrate need not be limited to GaAs; similar effects can be obtained with semiconductor substrates such as Si or InP, or dielectric substrates such as sapphire substrates.

[0037]

[Effects of the invention] (1) Unlike gas etching methods using chlorine gas or tetrafluorocarbon gas (CF4),
Does not generate highly reactive halogen radicals.

Therefore, gas etching and epitaxial crystal growth can be performed continuously while air is blocked, without causing problems such as abnormal adsorption phenomena inside the reactor that adversely affect the treatment process. Mixing of interfacial impurities caused by oxygen can be avoided.

In addition, reactive ion beam etching (R
Unlike the IBE) method, etc., etching can be performed with low energy, so damage to the sample can be kept to a minimum.

Therefore, III-V compound semiconductors and II
- Generation of interface states at the growth interface with the Group VI compound semiconductor can be suppressed, and optical loss caused by the interface states can be suppressed.

[0041] In addition, invalid recombination of electrons and holes caused by interface states can also be suppressed.

In other words, the current injected into the surface emitting semiconductor laser is converted into light with almost no loss, resulting in high efficiency characteristics.

Therefore, a surface emitting semiconductor laser having a low threshold current of 1 mA and a high differential quantum efficiency can be easily obtained.

[0044] Furthermore, it is possible to suppress the occurrence of dark line defects that originate from defects, and the life characteristics are improved.

In particular, the active layer contains Al0.15Ga0.85
When As is used, a life characteristic that is 10 times longer than that of the conventional one can be obtained. (2) The processing method is easy, does not require the creation or modification of a large-scale production line, and the initial investment for a semiconductor production line, which tends to be huge, can be suppressed.

[0046] Furthermore, the fact that the processing method is easy means that reproducibility is excellent and a stable and high yield can be obtained. (3) Compared to conventional gas etching, the selection ratio between the substrate and the mask can be significantly increased.

Therefore, pattern errors caused by the thickness of the mask can be eliminated, and precise patterns can be created.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process cross-sectional view for explaining the manufacturing process when using the method for manufacturing a surface emitting semiconductor laser of the present invention.

FIG. 2 is a perspective view showing a cross section of a surface emitting semiconductor laser light emitting section manufactured by the surface emitting semiconductor laser manufacturing method of the present invention.

FIG. 3 is a diagram showing the relationship between driving current and oscillation light output of a surface emitting semiconductor laser manufactured by the method for manufacturing a surface emitting semiconductor laser of the present invention.

[Explanation of symbols]

(101) n-type ohmic electrode (102) n-type GaAs substrate (103) n-type GaAs buffer layer (104) distributed reflection multilayer mirror (105) n-type Al0.1 Ga0.9 As cladding layer (106) p-type GaAs active layer (107) p-type Al0.4 Ga0.6 As cladding layer (108) p-type Al0.1 Ga0.9 As contact layer (109) ZnS0.06Se0.94 layer (11
0) P-type ohmic electrode (111) Dielectric multilayer film (112) SiO2 pattern

Claims (1)

[Claims] 1. A substrate-side reflector made of a III-V compound semiconductor on a substrate made of a semiconductor or dielectric in a direction perpendicular to the main surface of the substrate, and a part or whole made of a III-V compound semiconductor. In a method for manufacturing a surface-emitting semiconductor laser having a resonator having an active layer processed into a columnar shape by gas etching using an etching mask and a surface-side reflector made of a semiconductor, dielectric, or metal, the active layer is An etching gas containing dimethylzinc, diethylzinc, or an organic zinc compound is used during gas etching, and the material of the etching mask is an insulator such as photoresist, silicon oxide, or silicon nitride, or a metal such as molybdenum or nickel. A method of manufacturing a surface emitting semiconductor laser, characterized in that: