JPH02260667A - Compound semiconductor solar cell on silicon substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a solar cell immune from cracks, a factor of leakage, and deterioration in junction characteristics at the connection of two or more solar cells by a method wherein a welding pad is formed separate from an epitaxial crystal layer. CONSTITUTION:An Si substrate 1 is selectively etched to form a step of a forward mesa. Then, an SiO film 10 is selectively formed only on the lower part on the step. An N-type GaAs layer 2, a P-type GaAs layer 3, and a P-type Al0.85Ga0.15As window layer 4 are grown thereon. At this point, an epitaxial growth does not take place on the film 10. An SiN reflection preventive film 5 is formed on the whole face of the substrate 1. Then, after a hole is bored, a P-type electrode 6 and a welding pad 8 are formed, an N-type electrode 7 is built on the rear of the substrate 1, and lastly an interconnector 9 is welded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a solar cell formed by forming a compound semiconductor such as GaAs on a Si substrate and a method for manufacturing the same, and particularly relates to a method for manufacturing the same, in which a plurality of GaAs solar cells are formed on a Si substrate. This invention relates to an improved battery structure for suppressing characteristic deterioration when connecting individual batteries.

[Prior Art] FIG. 2 is a cross-sectional view showing a method of connecting a GaAs solar cell on a Si substrate manufactured by a conventional method.
is a Si substrate, 2 is an n-type GaAs layer, 3 is a p-type Ga
As layer, 4 is p-type A lo, ssG a o, +
sAs window layer, 5 is S i 3 N- antireflection film, 6 is p
7 is an n-type electrode, 8 is a welding pad, and 9 is an interconnector.

This conventional GaAs solar cell has an MOC on a Si substrate 1.
An n-type GaAs layer 2. is formed by the VD method. P-type GaAs1i3.
P-type Alo, ssG ao, and 15A S window layers 4 are sequentially formed. Then, an antireflection film 5 of 5 izN is formed on the entire surface. Next, p-type Al 6. ssc ao, +
sAs window layer 4. 'Si, N4 anti-reflection film 5 is opened at required locations, a p-type electrode 6 and a welding pad 8 are formed, and finally an n-type electrode is formed on the back surface of the substrate.

Next, a method of connecting the cells will be explained.

Is it formed on the p-type GaAs layer 3 of one solar cell? The interconnector 9 welded to the connection pad 8 is welded to the n-type electrode 7 of the other solar cell. By repeatedly forming the above structure, a plurality of solar cells can be connected.

[Problem to be solved by the invention]

Conventional GaAs solar cells on silicon substrates are constructed as described above, so when the interconnector is welded to the welding pad, cracks occur in the epitaxial crystal layer on the Si substrate due to pressure and strain, resulting in leakage. There have been problems such as deterioration of the bonding characteristics between the p-type GaAS layer 3 and the n-type CyaAs layer 2.

This invention was made in order to solve the problems of the conventional ones as described above, and there is no cranking when connecting multiple solar cells, there is no cause of leakage (and there is no deterioration of bonding characteristics). The purpose of the present invention is to obtain a compound semiconductor solar cell on a silicon substrate and a method for manufacturing the same that does not cause the formation of a compound semiconductor solar cell on a silicon substrate.

[Means to solve the problem]

A compound semiconductor solar cell on a silicon substrate and a method for manufacturing the same according to the present invention include forming a first insulating film partially on a forward mesa step formed in advance on a Si substrate or on the surface of a flat silicon substrate; In addition to forming a welding pad part, an epitaxial crystal layer is formed by selective growth, its sloped side part or vertical side part is protected with an insulating film, and a second conductivity type electrode is placed thereon to form an interconnector and a second Only the conductive type compound semiconductor layer is made conductive.

[Effect]

In this invention, since the welding pad portion is formed separately from the epitaxial crystal layer, no pressure or strain is applied to the epitaxial crystal layer during interconnect welding, and therefore cranking does not occur. Not,
There is no leakage factor and no deterioration of bonding characteristics.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a compound semiconductor solar cell on a silicon substrate manufactured by the method of one embodiment of the present invention, and in the figure, 1 is S
i substrate, 2 is n-type GaAsJli, 3 is p-type GaAs layer, 4 is p-type AI! o, ss G a o, t'
sAs window layer, 5 is Si, N, antireflection film, 6 is a p-type electrode, 7 is an n-type electrode, 8 is a welding pad, 9 is an interconnector, and 10 is an SiO□ film.

Next, the manufacturing method will be explained. First, the Si substrate 1 is selectively etched using a KOH aqueous solution or the like to form a mesa step. Next, for example, a thermal oxidation method is used to selectively form the SiO□ film 10 only on the lower part of the film layer 0. On top of this, by MOCVD method, n
type GaAs layer 2. P-type GaAs layer 3. P-type Al 6.
lls Gao, H5A s window layer 4 is grown. At this time, epitaxial growth does not occur on the Sin film 10. Then, a Si2N4 antireflection film 5 is formed on the entire surface. Next, after drilling, p-type electrode 6. Welding pad 8
, an n-type electrode 7 is formed on the back surface of the substrate, and finally an interconnector 9 is welded.

In a method for fabricating a GaAs solar cell on a silicon substrate according to an embodiment of the present invention, selective etching of the Si substrate is necessary to form the steps of the forward mesa. Also, Si
The film 10 serves as a selective growth layer of GaAs and as an insulator to separate the welding pad from the n-type Si.

Also Si3N.

The anti-reflection film 5 serves as a protective film for the junction between the n-type and n-type GaAs layers 2 and 3, and also serves as a welding pad 8 for the n-type GaAs layer 2.
It serves as an insulator to separate the

Further, FIG. 3 shows a compound semiconductor solar cell on a silicon substrate according to another embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 1 indicate the same parts.

Next, the manufacturing method will be explained. First, a SiO□ film 10 is selectively formed on a Si substrate 1 by, for example, a thermal oxidation method. The remaining portion is covered with an n-type (first conductivity type) GaAs layer 2. by MOCVD. p-type (second conductivity type) GaAs layer 3.
A P-type A lo, ssG ao, +sAs window layer 4 is grown. and on 5in2 membrane lO and 5i
By selectively etching and removing only the vicinity of the interface between the Oz film 10 and the epitaxial layer, the Sin film 10
The polyGaAs grains attached thereto are removed and the side surfaces of the epitaxial layer are exposed (hereinafter referred to as side exposure).

Next, after drilling, p-type electrode 6. A welding pad 8 is formed, and an n-type electrode 7 is formed on the back surface. Finally, the interconnector 9 is welded.

In this embodiment, the 5tot film 10 is used for selective growth of GaAs and also serves as an insulator to separate the welding pad 8 from the Si substrate. The process of selectively etching only the vicinity of the interface between the SiO□ film 10 and the epitaxial layer down to the Si substrate is performed using a high-quality n-type GaAs layer 3 and an n-type GaAs layer.
This is useful for exposing the side surface of the joint with the s-layer 2.

The S i 3 N4 antireflection film 5 is also an n-type GaAs layer 3
It serves as a protective film at the junction between the welding pad 8 and the n-type GaAs layer 2, and serves as an insulator to separate the welding pad 8 and the n-type GaAs layer 2.

In the above embodiment, Si, N, and SiO□ were used for the antireflection film 5, and SiO□ was used for the insulating film, but these were made from Tas
S, Affi, 0. It does not matter if it is a uniform substance.

Furthermore, in the above embodiment, G on the p-on-n type St substrate is
I explained about the aA s solar cell, but this is no
The present invention may be of the n-p type, and can be applied to any semiconductor device that requires damage reduction during welding, such as an InP solar cell on an St substrate, and provides the same effects as the above embodiments.

〔Effect of the invention〕

As described above, according to the compound semiconductor solar cell on a silicon substrate and the method for manufacturing the same according to the present invention, a Si substrate is used, a first insulating film is formed on a part of the silicon substrate, and an epitaxial crystal layer is formed on the other part. Also, since the joint portion of the first and second conductivity type compound semiconductor crystal layers is protected by the second insulating film, and the welding pad is formed on the first insulating film,
There is also no cranking during interconnector welding, and there is no deterioration of bonding characteristics.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a method for manufacturing a compound semiconductor solar cell on a silicon substrate according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a method for manufacturing a GaAs solar cell on a silicon substrate by a conventional method, and FIG. FIG. 3 is a cross-sectional view showing a method for manufacturing a compound semiconductor solar cell on a silicon substrate according to another embodiment of the present invention. In the figure, 1 is a Si substrate, 2 is an n-type GaAs layer, 3 is a p-type CaAs layer, 4 is a p-type A lo, asG ao
, +sAs window layer, 5 is a Si*N4 antireflection film, 6 is a p-type electrode, 7 is an n-type electrode, 8 is a welding pad, 9 is an interconnector, and IO is a Sin film. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A first insulating film partially formed on the lower part of the forward mesa step on the silicon substrate or on the surface of the planar silicon substrate, and a first insulating film formed by selective growth on the silicon substrate excluding the first insulating film. a second insulating film provided to cover first and second conductivity type compound semiconductor crystal layers for photoelectric conversion; and a second insulating film provided to cover inclined side surfaces or vertical side surfaces of both of the compound semiconductor crystal layers; an interconnector provided on the insulating film of No. 2 for electrical connection with other solar cells, and an electrode of a second conductivity type that conducts only the compound semiconductor layer of the second conductivity type in the compound semiconductor crystal layer; A compound semiconductor solar cell on a silicon substrate, characterized in that the interconnector and the second conductivity type electrode are welded to a welding pad portion on the first insulating film. (2) forming a first insulating film partially on the lower part of the forward mesa step on the silicon substrate or on the surface of the flat silicon substrate; a step of selectively growing a compound semiconductor crystal layer of a second conductivity type; a step of forming an inclined side surface portion or a vertical side surface portion in the first and second conductivity type compound semiconductor crystal layers; forming a second insulating film covering the vertical side surface; and forming an interconnector for electrical connection with another solar cell on the second insulating film, and forming a second insulating film in the epitaxial crystal compound semiconductor layer. forming a second conductivity type electrode that conducts only the second conductivity type compound semiconductor layer; forming a welding pad portion on the first insulating film; and forming a welding pad portion on the welding pad portion. A method for manufacturing a compound semiconductor solar cell on a silicon substrate, comprising the step of welding a connector and the electrode of the second conductivity type.