JPH02228076A - Optoelectric transducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrode structure of a photoelectric conversion element.

[Conventional technology]

FIG. 3 is a cross-sectional view of a GaAs solar cell on a Si substrate as an example of a conventional photoelectric conversion element.

In the figure, 1 is an n-type Si substrate (hereinafter referred to as rsi substrate).
2 is an n-type GaAs layer (hereinafter simply referred to as "n layer") selectively epitaxially grown on the first surface of the Si substrate by MBE or MOCVD.
, 3 is a p-type GaAs layer grown on the nN2 layer (hereinafter simply referred to as "p layer"), 4 is a p-type Al layer grown on the 2 layer 3
GaAs window layer (hereinafter simply referred to as "window layer"), 5 is window layer 4
Si nitride film (hereinafter referred to as rAR film) for antireflection formed by photo-CVD method or vapor deposition method after growth
, 6 is a p-electrode formed on the two layers 3 by vapor deposition or sputtering through contact holes selectively formed by etching the AR film 5 and the window layer 4, and 7 is an S
An n electrode 8 formed on the second surface of the i-substrate 1 is a double layer 3
This is a welding electrode formed on the AR film on the Si substrate 1 from the upper p-electrode 6. 9a or 9b is an interconnector that connects the welding electrode 8 and the n-electrode 7 of another solar cell, or the n-electrode 7 and the welding electrode 8 of another solar cell. Interconnectors 9b and 9a are fixed to n-electrode 7 and welding electrode 8 by welding.

Next, the operation will be explained. The light incident on the GaAs layer is divided into two layers 3. Photocarriers are generated in the n-layer 2. Among the generated photocarriers, only those carriers that have reached the pn junction surface through diffusion contribute to the photocurrent. Photocurrent is p electrode 6+
Output from the n electrode 7 to the interconnectors 9a, 9
b to other solar cells and external circuits.

In a GaAs solar cell on a Si substrate, if the interconnector 9a is welded directly to the p-electrode 6, cracks will occur in the GaAs layer under the p-electrode 6 due to thermal stress during welding due to the difference in thermal expansion coefficient between Si and GaAs0. It ends up. Therefore, the interconnector 9a is welded to the welding electrode 8 formed as an ARRb2 insulating film on the Si substrate 1. This welding electrode 8 is electrically connected to p[i6.

[Problem to be solved by the invention]

Since the conventional photoelectric conversion element is configured as described above, the insulating film also serves as ARRb2, so the insulating film cannot be made thicker. Therefore, there is a problem in the pressure resistance between the welding electrode 8 and the Si substrate 1. Besides, ARRb2CV
Since it is formed by the D method, vapor deposition method, etc., the adhesive strength between the interconnector 9a and the Si substrate 1 is not very high, and when a large force is applied to the interconnector 9a, the electrodes and the Si substrate 1
There were problems such as peeling off.

The present invention has been made in view of these points, and its purpose is to increase the adhesive strength between the Si substrate and the insulating film, and to increase the withstand voltage between the welding electrode and the Si substrate. The object of the present invention is to obtain a photoelectric conversion element that can improve performance.

[Means to solve the problem]

In order to achieve such an object, the present invention includes a Si substrate,
M having a pn junction selectively formed on this Si substrate
- A photoelectric conversion element consisting of a V group compound semiconductor layer, which includes a thermally oxidized Si film selectively formed on a Si substrate, and an electrode formed on this thermally oxidized Si film removed, and an interconnector to this electrode. It is designed to weld.

[Effect]

The photoelectric conversion element according to the present invention has high adhesion strength between the Si substrate and the insulating film, and the insulating film is thick and has high pressure resistance.

〔Example〕

An embodiment of the photoelectric conversion element according to the present invention will be described.

Figure 1 shows a GaAs substrate on a Si substrate, which is an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a solar cell. In this figure, the same parts or equivalent parts as in Fig. 3 are given the same reference numerals, and 10 is AR.
This is a thermally oxidized Si film (hereinafter referred to as "thermal oxidized film") that is selectively formed by thermal oxidation on a Si substrate l by Rb2 etching.

Thermal oxide film 10 is formed using a chemical method such as a photo-CVD method or a sputtering method.
The adhesive strength is greater than that of a physically debossed film, and the welding electrode 8 will not peel off from the Si substrate when force is applied to the interconnector 9a. Furthermore, since it is formed by thermal oxidation, it can be formed selectively only on the Si substrate l and to any desired thickness. Therefore, without impairing the effect of reducing reflection by ARRb2, welding electrode 8 and S
It is possible to obtain a thermal oxide film lO having a thickness sufficient to withstand the voltage between the i-substrates.

In the above embodiment, the welding electrode 8 is formed separately after the p-electrode 6 is formed, but the p-electrode 6 and the welding electrode 8 may be formed integrally. FIG. 2 is a cross-sectional view of a GaAs solar cell on a Si substrate, which is another embodiment of the present invention.

In FIG. 2, the same parts or equivalent parts as in FIG. This is a p-electrode that is integrally wired up to the top of the oxide film 10. The interconnector 9a is welded to the portion of the p-electrode 11 wired on the thermal oxide film 10.

In this embodiment, since the p-electrode 11 also serves as a welding electrode, the number of steps can be reduced. Furthermore, it is possible to avoid the risk of poor electrical contact between the p-electrode and the welding electrode, which would otherwise occur if they were formed separately.

〔Effect of the invention〕

As explained above, the present invention provides the electrode for welding the interconnector on the thermally oxidized Si film selectively formed on the Si substrate, thereby increasing the adhesive strength to the Si substrate (
Furthermore, since the thickness of the thermally oxidized Si film can be made arbitrarily thick, there is an effect that the pressure resistance between the electrode and the Si substrate can be increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a photoelectric conversion element according to the present invention, FIG. 2 is a sectional view showing a second embodiment of the invention, and FIG. 3 is a sectional view showing a conventional photoelectric conversion element. be. ■...Si substrate, 2...n layer, 3...p layer, 4...
...Window layer, 5...AR film, 6...p electrode, 7...
n electrode, 8... welding electrode, 9a, 9b... interconnector, 10... thermal oxide film.

Claims (1)

[Claims] In a photoelectric conversion element comprising a Si substrate and a III-V group compound semiconductor layer selectively formed on the Si substrate and having a pn junction, a thermally oxidized Si film selectively formed on the Si substrate; A photoelectric conversion element comprising an electrode formed on the thermally oxidized Si film, and an interconnector welded to the electrode.