JPS5916402B2 - GaAlAs etching solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 9GaAlAs etching solution suitable for protruding etch pits on the surface of a Ga11AtXAS layer (or substrate) or performing mesa etching.

For example, when a semiconductor laser is operated, a dark spot or dark lie appears in the emission spectrum;

It is presumed that the cause is dislocations, defects, etc. occurring in the -V group compound semiconductor crystal such as Ga1-xAtxAs. Furthermore, since these dislocations are related to etch pits, it is thought that the crystal can be evaluated by observing the number of etch pits per unit area of the Ga1, xAtXAs layer, for example. . However, conventionally, there has been no method for making etch pits appear on the surface of the Ga11AιxAs layer, and the evaluation of the crystal as described above has been considered to be merely theoretical.

The present invention aims to make it possible to observe the number of etch pits in Gal-xAlxAs crystals used in semiconductor lasers, light-emitting diodes, etc.
S-layer (or substrate) (water/hydrogen peroxide/hydrofluoric acid/acetic acid)
The present invention provides a GaAtAs etching solution characterized by having a composition of 0, which will be described in detail below. Gal-xAtx with the GaAtAs etching solution of the present invention
When the As layer (or substrate) is etched, etch pits can appear on the surface.

In addition, a secondary effect, which was not expected at the beginning, was also obtained: extremely good mesa etching was possible. In the present invention, as described above, water (H2O) / hydrogen peroxide (H2O2) / hydrofluoric acid (HF) / acetic acid (CH3C00H)
Gal-xAtxAs0 with an etching solution having the composition
The basic idea is to etch layers.

In order to perform etching with this etching solution and make it possible to observe etch pits, a predetermined allowable mixing ratio exists. That is, as a volume ratio at room temperature, 5H20:0
~3.0 H202: 0.3~3.0 (30") HF: 0.
1-3.0 (50%) CH3COOH: 1.0 (
99.5%).

When etching is performed with an etching solution having this composition, the etching speed is 1.5 [μm/min] to 20 [μm/min].
μm/min].

Also, the amount of Al in Gal-XAlxAs is 0 as x value
．． Etchipits can be observed well when the value is in the range of 0.05 to 1.0.

The etch pits that appear when the Gal-XAlxAs layer is etched with the etching solution have a conical shape.

Photo 1 shows Gal-XAlx grown liquid-phase epitaxially on a GaAs substrate with a top surface index of (100).
The surface of the As layer was etched with the etching solution, and
The image was taken with double magnification.

Symbols 1 to 9 indicate portions of etch pits.

Photo 2 is a 200x enlargement of a part of Photo 1, and the same symbols indicate the same parts.

In order to correlate etipits and dislocations, the present inventors performed measurements using transmission X-ray topography on the sample shown in Photo 1, and obtained a dislocation image as seen in Photo 3.

As can be seen by comparing Photos 1 and 3, one end of the dislocation image ends with an etchipit image. Furthermore, by performing transmission X-ray topography measurements on different crystal planes, it was confirmed that other etching pits also correspond to dislocations. Therefore, by observing the number of etchipts, it is possible to know the amount of dislocations and to evaluate the quality of the crystal. By the way, using the above etching solution, Gal-
It has been found that good mesa etching of an 0A1xAs layer (x=0-1.0) can be performed.

Conventionally, when mesa-etching a Gal-XAlxAs layer, a Gal-XAlxAs layer 12 grown by liquid phase epitaxial growth on a GaAs substrate 11 is removed, as shown in FIG.
The mask 13 is generally hollowed out to the bottom, so-called over-etching.

Photo 4 shows GaO. 9AlO. lAs crystal layer with NH4OH
/H2O2 type etching solution represents a side cross section when mesa etching is performed. Although the photograph lacks clarity, it is clear that the arrow indicates the tip of the gold (Au)-zinc (Zn) electrode, and that it has been over-etched as explained in connection with Figure 1. can. On the other hand, in the etching solution of the present invention, if the composition of the etching solution is appropriately selected, mesa etching can be performed in which the bottom of the mask 13 is not gouged out at all, as shown in FIG.

Furthermore, since the etching solution does not attack the Au-Zn electrode at all, the electrode itself can be used as a mask.
In FIG. 2, the same parts as those explained with reference to FIG. 1 are indicated by the same symbols. Photo 5 is similar to photo 4, with GaO. , AlO. lAs crystal layer with H2O/H2O2
/HF/CH3COOH=0.5/0.5/0.25/
This is a photograph of a side cross section when mesa etching was performed using an etching solution with composition No. 1, and the arrow indicates Au-Zn.
At the tip of the electrode, there is no over-etching, as described with respect to FIG. 3 to 7 respectively show GaO. 95AlO. O5AS crystal layer (100) plane, GaO. 5AM. , As crystal layer (10
0) surface, GaO. 7lAlO. 29AS crystal layer (100
) surface, GaO. 38AlO. 62AS crystal layer (100)
surface, GaO. 2AlO. 8As crystal layer (100) plane H
2O/H2O2/HF/CH3COOH=0.5/0.
This is a micrograph showing an etch pit etched with an etching solution having a composition of 5/0.25/1.

FIG. 3, that is, GaO. 95AtO. Regarding the O5AS crystal layer (x=0,05), the etching time was 4 minutes, and the imaging magnification was 500x.

FIG. 4, that is, GaO. 5AlO. 5As crystal layer (x
=0.5), the etching time is 5 minutes and the imaging magnification is 500x. Figure 5:
GaO. 7lAlO. 29AS crystal layer (x=0.29)
The etching time was 5 minutes, and the photographing magnification was 500 times.

FIG. 6, that is, GaO. 38AlO. Regarding the 62AS crystal layer (x=0.62), the etching time was 5 minutes, and the imaging magnification was 500x. FIG. 7, that is, GaO. 2AlO. Regarding the 8As crystal layer (XO.8), the etching time was 4 minutes, and the photographing magnification was 500 times. In this way, Gal-XAtX
Even when the amount of Al in the AS is x value other than 0.1 as explained in relation to Photo 4, the etched pit can be observed well.

As can be seen from the above explanation, according to the present invention, it is possible to easily reveal the etch pits on the surface of the Gal-XAlxAs layer, which was difficult in the past, and by observing the number of etch pits, it is possible to By accurately determining quality in advance and using only high-quality crystals, it is possible to manufacture long-life semiconductor devices, such as semiconductor lasers.

Further, if mesa etching is performed using the etching solution of the present invention, the underside of the mask will not be over-etched, and it is possible to obtain a desired mesa shape.

[Brief explanation of the drawings] Figure 1 is a side sectional view of the main part explaining the conventional mesa shape, Figure 2
The figure is a sectional side view of a main part explaining the mesa shape of an embodiment of the present invention, and FIGS. 3 to 7 are microscopic photographs taken of the surface of the main part of the GaAlAs crystal layer after being etched. In the figure, 11 is the substrate, 12 is Gal-XAtXAs
Layer 13 indicates a mask, respectively.

Claims (1)

[Claims] 1 Ga_1_-_xAl_xAs layer or substrate (0
<x<1.0), which has a volume ratio at room temperature of H_2O:0 to 3.0 H_2O_2:0.3 to 3.0 (30%) HF:
0.1-3.0 (50%) CH_3COOH: 1
．． 0 (99.5%)
AlAs etching solution.