JP7290939B2 - Group III-V compound semiconductor solar cells and satellites - Google Patents

Description

The present invention relates to III-V compound semiconductor solar cells and satellites.

In recent years, III-V group compound semiconductor solar cells are known as solar cells mounted on artificial satellites. Such a group III-V compound semiconductor solar cell is disclosed in Patent Document 1, for example.

Patent Document 1 describes a compound semiconductor solar cell composed of subcell A/subcell B/subcell C formed on a substrate. A back surface field (BSF) layer of GaInAsP is deposited on the base layer of subcell C composed of GaInAs, over which is deposited a p+ contact layer of p+ type InGaAs, on which a metal contact layer is deposited. It is Also, subcell B and subcell C are lattice mismatched and composed of graded InGaAlAs with a monotonically varying lattice constant to achieve a lattice constant transition from subcell B to subcell C. A technique for forming a metamorphic buffer layer is disclosed.

JP 2007-324563 A

For III-V group compound semiconductor solar cells, a technique for reducing the thickness of the solar cell layer is required in order to reduce the cost.

In order to solve the above problems, a III-V group compound semiconductor solar cell according to an aspect of the present invention includes a first electrode, a contact layer provided on the first electrode, and a contact layer provided on the contact layer. a first cell containing a group III-V compound semiconductor provided on the buffer layer; and a second electrode provided on the first cell; the contact layer; The lattice constant of the buffer layer is different from that of the first cell, and the lattice constant of the buffer layer is closer to the lattice constant of the first cell than the lattice constant of the contact layer at least on the first cell side.

According to one aspect of the present invention, it is possible to reduce the thickness of the solar cell without deteriorating the characteristics of the solar cell.

1 is a schematic cross-sectional configuration diagram of a III-V group compound semiconductor solar cell of Embodiment 1. FIG. 1 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 1. FIG. 1 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 1. FIG. 1 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 1. FIG. 2 is a schematic cross-sectional configuration diagram of a III-V group compound semiconductor solar cell of Embodiment 2. FIG. FIG. 10 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 3; FIG. 10 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 3; FIG. 10 is a schematic cross-sectional configuration diagram for explaining an example of a method for manufacturing a group III-V compound semiconductor solar cell of Embodiment 3; FIG. 10 is a schematic cross-sectional configuration diagram of a III-V group compound semiconductor solar cell of Embodiment 4; (a) is a schematic perspective view of a satellite of Embodiment 5; (b) is a schematic plan view of a solar cell array of Embodiment 5 used in the satellite of Embodiment 5; ) is a schematic plan view of the III-V group compound semiconductor solar cells of Embodiments 1 to 4 used in the solar cell array of Embodiment 5. FIG.

Embodiments will be described below. In the drawings used for describing the embodiments, the same reference numerals denote the same or corresponding parts. In the following description, the terms “upper”, “lower”, etc. will be used, but this is only for the convenience of explanation. The direction is not limited.

<Embodiment 1>
FIG. 1 shows a schematic cross-sectional view of the III-V group compound semiconductor solar cell of Embodiment 1. As shown in FIG. The III-V group compound semiconductor solar cell of this embodiment includes a first electrode 102, a contact layer 103 provided on the first electrode 102, a buffer layer 199 provided on the contact layer 103, and a buffer layer 199 It has a first cell 131 provided thereon and a second electrode 121 provided on the first cell 131 . The lattice constants of the contact layer 103 and the first cell 131 are different, and the lattice constant of the buffer layer 199 is greater than that of the first cell 131 than that of the contact layer 103 at least on the first cell 131 side. values close to each other. A specific configuration of the group III-V compound semiconductor solar cell of this embodiment is shown below.

As shown in FIG. 1, in the III-V group compound semiconductor solar cell of Embodiment 1, on a support substrate 101, a metal layer 102 (electrode) as a first electrode 102 and a p-type contact layer as a contact layer 103 are formed. 103, buffer layer 199, and first cell 131 are laminated in this order.

The first cell 131 (bottom cell 131) includes, for example, a p-type BSF layer 104 having a lattice constant that is the same as or approximately the same as the lattice constant of the p-type base layer 105 made of p-type InGaAs, a p-type base layer 105, and an n-type emitter. It has a structure in which layer 106 and n-type window layer 107 are laminated in this order.

The p-type contact layer 103 is made of p-type GaAs, for example. Also, the buffer layer 199 is made of, for example, p-type AlInAs. The p-type contact layer 103 and the p-type BSF layer 104 have different lattice constants. Moreover, the lattice constant of the buffer layer 199 is closer to the lattice constant of the p-type BSF layer 104 than the lattice constant of the p-type contact layer 103 at least on the p-type BSF layer 104 side.

The In composition ratio of the buffer layer 199 of this embodiment changes from the p-type contact layer 103 side to the p-type BSF layer 104 side. The lattice constant of the buffer layer 199 changes with the In composition ratio of the buffer layer 199 . Specifically, the In composition ratio of the buffer layer 199 changes (decreases) from n-type Al _0.38 In _0.62 As to n-type Al _0.69 In _0.31 As. As a result, of the lattice constant of the buffer layer 199 , at least the portion in contact with the p-type BSF layer 104 has the same or approximately the same lattice constant as the p-type BSF layer 104 . In addition, among the lattice constants of the buffer layer 199 , at least the portions in contact with the p-type contact layer 103 have the same or approximately the same lattice constant as the p-type contact layer 103 .

Further, the thickness of the buffer layer 199 made of p-type AlInAs in this embodiment is preferably 0.5 μm to 1 μm. Thereby, the lattice constant of the buffer layer 199 can be gently changed from the p-type contact layer 103 side to the p-type BSF layer 104 while suppressing the thickness of the buffer layer 199 . As a result, it is possible to suppress the occurrence of lattice defects in the buffer layer 199 while suppressing the thickness of the buffer layer 199 . However, the thickness of the buffer layer 199 may be less than 0.5 μm and may be greater than 1 μm.

The In composition ratio of the buffer layer 199 made of p-type AlInAs is preferably changed linearly (decreased monotonously) from the p-type contact layer 103 side to the p-type BSF layer 104 side. As a result, the lattice constant of the buffer layer 199 changes linearly (monotonic decrease), so that rapid changes in the lattice constant of the buffer layer 199 can be suppressed, and lattice defects in the buffer layer 199 can be suppressed. As a result, lattice defects generated in the buffer layer 199 can be suppressed from propagating to layers above the buffer layer 199, and degradation of solar cell characteristics can be suppressed. However, the lattice constant of the buffer layer 199 may be changed curvilinearly by changing the In composition ratio of the buffer layer 199 curvilinearly. Also, the lattice constant of the buffer layer 199 may be changed stepwise by changing the In composition ratio of the buffer layer 199 stepwise.

An n-type buffer layer 108 is laminated on the n-type window layer 107 . In this embodiment, the n-type buffer layer 108 is composed of n-type InGaP. The In composition ratio of the n-type buffer layer 108 changes from the n-type window layer 107 side to the tunnel junction layer 109 . The In composition ratio of the n-type buffer layer 108 changes (decreases) from n-type In _0.82 Ga _0.18 P to n-type In _0.48 Ga _0.52 P from the window layer 107 side to the tunnel junction layer 109 side, for example. The In composition ratio of the n-type buffer layer 108 may be changed continuously (monotonic decrease) or may be changed stepwise.

A tunnel junction layer 109 is formed on the n-type buffer layer 108 by laminating an n-type layer and a p-type layer in this order.

A second cell 132 (middle cell 132 ) is laminated on the tunnel junction layer 109 . The middle cell 132 includes a p-type BSF layer 110 having a lattice constant the same as or similar to that of the p-type base layer 111 made of p-type GaAs, a p-type base layer 111, an n-type emitter layer 112, and an n-type window layer 113 in this order. It has a laminated structure. Note that the n-type layer and the p-type layer of the tunnel junction layer 109 also have lattice constants that are the same as or similar to that of the p-type base layer 111 .

On the n-type window layer 113, a tunnel junction layer 114 is formed by laminating an n-type layer and a p-type layer in this order.

A third cell 133 (top cell 133 ) is laminated on the tunnel junction layer 114 . The top cell 133 includes a p-type BSF layer 115, a p-type base layer 116, an n-type emitter layer 117, and an n-type window layer 118 having the same lattice constant as or approximately the same as the p-type base layer 116 made of p-type InGaP. It has the structure laminated|stacked in order.

An n-type contact layer 119 and an antireflection film 120 are provided on the n-type window layer 118 , and a metal layer 121 (electrode) as a second electrode 121 is provided on the n-type contact layer 119 .

Next, an example of a method for manufacturing the group III-V compound semiconductor solar cell of Embodiment 1 will be described with reference to schematic cross-sectional views of FIGS.

First, as shown in FIG. 2, a GaAs substrate 122 is placed in an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and an etching stop layer 123 and an n-type contact layer 119 which can be selectively etched with GaAs are formed on the GaAs substrate 122. , n-type window layer 118, n-type emitter layer 117, p-type base layer 116 and p-type BSF layer 115 are epitaxially grown in this order by MOCVD.

Next, a tunnel junction layer 114 is formed on the p-type BSF layer 115 by MOCVD.

Next, on tunnel junction layer 114, n-type window layer 113, n-type emitter layer 112, p-type base layer 111 and p-type BSF layer 110 are epitaxially grown in this order by MOCVD.

Next, a tunnel junction layer 109 is formed on the p-type BSF layer 110 by MOCVD.

Next, an n-type buffer layer 108 is epitaxially grown on the tunnel junction layer 109 by MOCVD. In this embodiment, the n-type buffer layer 108 adjusts the flow rates of TMI (trimethylindium) and TMG (trimethylgallium) as group III element gases so that n-type InGaP is grown. Then, introduction of the growth gas whose flow rate has been adjusted into the chamber is started. Then, while introducing the growth gas into the chamber, the ratio of the flow rate of TMI to the total flow rate of TMI and TMG in the growth gas is changed. As a result, an n-type buffer layer with a varying In composition ratio is grown.

Next, on the n-type buffer layer 108, the n-type window layer 107, the n-type emitter layer 106, the p-type base layer 105 and the p-type BSF layer 104 are epitaxially grown in this order by MOCVD.

Next, a buffer layer 199 is epitaxially grown on the p-type BSF layer 104 by MOCVD. In this embodiment, the buffer layer 199 adjusts the flow rates of TMI (trimethylindium) and TMA (trimethylaluminum) as the Group III element gas so that p-type AlInAs is grown. Then, introduction of the growth gas whose flow rate has been adjusted into the chamber is started. Then, while introducing the growth gas into the chamber, the ratio of the flow rate of TMI to the total flow rate of TMI and TMA in the growth gas is changed. As a result, a buffer layer 199 with varying In composition ratio is grown.

Next, the n-type contact layer 103 is epitaxially grown on the buffer layer 199 by MOCVD.

In this embodiment, as the growth gas, for example, AsH ₃ (arsine) and TMG are used to form GaAs, TMI, TMG and PH ₃ (phosphine) are used to form InGaP, and TMI, TMG and _AsH3 are used, TMA (trimethylaluminum), TMI and _PH3 are used to form AlInP, TMA, TMG and _AsH3 are used to form AlGaAs, TMA, TMG and AsH3 are used to form AlInGaAs. TMI, TMG and _AsH3 can be used. The growth gas may also contain a gas such as an n-type or p-type dopant gas.

Next, as shown in FIG. 3, a metal layer 102 is formed on the p-type contact layer 103, and a support substrate 101 is attached on the metal layer 102. Next, as shown in FIG. The metal layer 102 is made of, for example, a laminate of Au and Ag.

Next, as shown in FIG. 4, after etching the GaAs substrate 122 with an alkaline aqueous solution, the etching stop layer 123 is etched with an acid aqueous solution.

Next, after forming a resist pattern on the n-type contact layer 119 made of n-type GaAs by photolithography, part of the n-type contact layer 119 is removed by etching using an alkaline aqueous solution. Then, a resist pattern is formed again on the surface of the remaining n-type contact layer 119 by photolithography, and a resist pattern and an EB (Electron Beam) vapor deposition device are used to form a laminate of, for example, AuGe/Ni/Au/Ag. A metal layer 121 consisting of a body is formed.

Next, after forming a mesa etching pattern, mesa etching is performed using an alkaline aqueous solution and an acid solution. Then, an antireflection film 120 is formed by forming a laminate of, for example, a TiO ₂ film and an Al ₂ O ₃ film by an electron beam (EB) vapor deposition method. As a result, the group III-V compound semiconductor solar cell of Embodiment 1 having the configuration shown in FIG. 1 in which the light-receiving surface of the compound semiconductor solar cell is located on the side opposite to the growth direction of the compound semiconductor can be obtained.

In the III-V group compound semiconductor solar cell of this embodiment, as described above, the p-type contact layer 103 made of p-type GaAs, the buffer layer 199 made of p-type AlInAs, the p-type BSF layer 104 made of p-type InGaAs, A bottom cell 131 made of InGaAs, a middle cell 132 made of GaAs, and a top cell 133 made of InGaP are stacked in this order.

The bandgap value of the material forming the p-type contact layer 103 is greater than or equal to the bandgap value of the material forming the middle cell 132 . That is, the material forming the p-type contact layer 103 is a material that can transmit light in the light wavelength range that the bottom cell 131 absorbs.

Specifically, in this embodiment, the bandgap of InGaAs forming the bottom cell 131 is approximately 1.0 eV, the bandgap of GaAs forming the middle cell 132 is approximately 1.42 eV, and the bandgap of GaAs forming the top cell 131 is approximately 1.42 eV. InGaP has a bandgap of about 1.9 eV. The bandgap of the p-type contact layer 103 made of p-type GaAs and the buffer layer 199 made of p-type AlInAs is 1.42 eV or more. That is, the material forming the middle cell 132 and the bandgap forming the p-type contact layer 103 are the same. The bandgap value of the material forming the buffer layer 199 is equal to or greater than the bandgap value of the material forming the middle cell 132 .

Therefore, the light in the light wavelength range absorbed by the bottom cell 131 reflected by the metal layer 102 is suppressed from being absorbed by the p-type contact layer 103 and the buffer layer 199 and reaches the bottom cell 131 . Therefore, light reflected by the metal layer 102 is efficiently absorbed by the bottom cell 131 . In this embodiment, the light wavelength range absorbed by the bottom cell 131 is 1.42 eV to 1.0 eV. As described above, in the present embodiment, the bottom cell 131 can absorb the light reflected by the metal layer 102, so that the thickness of the bottom cell 131 can be reduced.

In addition, since the III-V group compound semiconductor solar cell of the present embodiment uses the p-type contact layer 103 made of p-type GaAs, the p-type contact layer 103 and the metal layer 102 can be ohmic-connected.

By the way, the material that can transmit light in the light wavelength range absorbed by the bottom cell 131 made of InGaAs is GaAs, and the lattice constants of InGaAs and GaAs differ by about 2%. Therefore, when GaAs is used as the p-type contact layer 103, if the bottom cell 131 made of InGaAs is directly formed on the p-type contact layer 103, there is a concern that the crystallinity of InGaAs will be affected and the solar cell characteristics will be degraded. was there.

However, the III-V group compound semiconductor solar cell of this embodiment has a buffer layer 199 whose lattice constant changes continuously from the p-type contact layer 103 to the bottom cell 131 . Therefore, even when GaAs is used as the p-type contact layer 103, the occurrence of crystal defects in the bottom cell 131 can be suppressed. As a result, in the group III-V compound semiconductor solar cell of this embodiment, the thickness of the solar cell layer can be reduced without degrading the characteristics of the solar cell.

In the above description, InGaP is used as an example of the material forming the top cell 133 . however. The material forming the top cell 133 may be AlInGaP or AlGaP.

In the above description, the III-V group compound semiconductor solar cell was configured to have three cells, the bottom cell 131 , the middle cell 132 and the top cell 133 . However, the group III-V compound semiconductor solar cell may be configured with two cells or less, or may be configured with four cells or more.

In the above description, AlInAs is used as an example of the material forming the buffer layer 199 . However, the material forming the buffer layer 199 may be InGaP. In this case, the buffer layer 199 may be epitaxially grown by MOCVD using TMI and TMG as growth gases. Then, the lattice constant of the buffer layer 199 can be changed by changing the composition ratio of In by changing the flow rates of TMI and TMG. Also, the material forming the buffer layer 199 may be AlInGaP. In this case, the buffer layer 199 may be epitaxially grown by MOCVD using TMA, TMI, and TMG as growth gases. Then, the lattice constant of the buffer layer 199 can be changed by changing the composition ratio of In by changing the flow rates of TMA, TMI, and TMG.

Further, in the above description, the p-contact layer 103 is made of GaAs. However, the GaAs forming the p-contact layer 103 may contain a very small amount of substances such as In and Al, which do not affect the bandgap and lattice constant.

In the above description, the group III element whose composition changes is In, but is not limited to In. A group III element other than In (such as Al and/or Ga) can be used as a group III element whose composition changes. may be The composition of the Group III element can be identified by SIMS (secondary ion mass spectrometry), and the lattice constant can be derived from the composition of the Group III element identified by SIMS.

In addition, in this specification, when the chemical formula of a compound does not describe the composition ratio of the elements constituting the compound, and the composition is not particularly mentioned, the composition ratio is not particularly limited, and can be set as appropriate. means that it is possible.

In addition, even if the composition ratio of the elements constituting the compound is described in the chemical formula of the compound in this specification, the present invention is not limited to the constitution of the composition ratio.

<Embodiment 2>
FIG. 5 shows a schematic cross-sectional view of the III-V group compound semiconductor solar cell of Embodiment 2. As shown in FIG. In the III-V group compound semiconductor solar cell of Embodiment 2, a metal layer 1021 connected to the metal layer 102, which is the first electrode 102, is provided on the upper surface side (the side on which the second electrode 121 is provided). It is characterized by In other words, the group III-V compound semiconductor solar cell of Embodiment 2 is characterized in that the metal layer 1021 is provided on the side on which sunlight is incident. Since other configurations are the same as those of the III-V group compound semiconductor solar cell of Embodiment 1, description thereof is omitted.

In order to fabricate the III-V group compound semiconductor solar cell of Embodiment 2, first, according to Example 1, metal layer 102, p-type contact layer 103, buffer layer 199, bottom cell 131 are formed on supporting substrate 101. , n-type buffer layer 108, tunnel junction layer 109, middle cell 132, tunnel junction layer 114, top cell 133, n-type contact layer 119, and metal layer 121 are fabricated.

Next, the structure is etched from the metal layer 121 side with an alkaline aqueous solution or an acid aqueous solution until the p-type contact layer 103 is exposed. In this embodiment, GaAs is used for the p-type contact layer 103 and AlInAs is used for the buffer layer 199 . Therefore, the buffer layer 199 is selectively etched with respect to the p-type contact layer 103 .

Next, on the exposed surface (upper surface) of the p-type contact layer 103, for example, a 30 nm-thick Au film and a 5000 nm-thick Ag film are successively vapor-deposited, followed by heat treatment to form a metal layer 1021. FIG. By configuring the metal layer 1021 in this way, the resistance between the metal layer 1021 and the metal layer 102 can be reduced.

Next, according to the first embodiment, an antireflection film 120 is formed. Thus, the III-V group compound semiconductor solar cell of Embodiment 2 is produced.

According to the III-V group compound semiconductor solar cell of Embodiment 2, since it is not necessary to wire or the like from the back surface side (lower surface side) of the support substrate 101, the thickness can be further reduced and the structure can be simplified. Become.

In the second embodiment, the method of forming the metal layer 1021 by exposing the p-type contact layer 103 by etching after forming the metal layer 121 has been described. However, after forming the n-type contact layer 119, the p-type contact layer 103 may be exposed by etching, the metal layer 1021 may be formed, and then the metal layer 121 and the antireflection film 120 may be provided.

In addition, in the second embodiment, a configuration in which an Au film and an Ag film are laminated as the metal layer 1021 has been described, but other metal films, ZnO (zinc oxide), SnO ₂ (tin oxide), or ITO (Indium Tin Oxide) may be used. ) and other transparent conductive materials may be used.

Also, in the second embodiment, an example in which AlInAs is used for the buffer layer 199 has been described. However, the material of the buffer layer 199 may be any material that can be selectively etched with the p-type contact layer 103, such as InGaP or AlInGaP.

<Embodiment 3>
6 to 8 show schematic cross-sectional configuration diagrams for explaining an example of the method for manufacturing the group III-V compound semiconductor solar cell of the second embodiment. The III-V group compound semiconductor solar cell of Embodiment 3 is formed by growing a compound semiconductor layer on a Ge substrate 201, and is characterized in that the lattice constant of each cell is matched to that of Ge. Other structures conform to the first embodiment.

First, as shown in FIG. 6, an etching stop layer 123 having a lattice constant similar to that of Ge, an n-type contact layer 119, and a base layer 116 made of p-type InGaP are formed on a Ge substrate 201. Alternatively, an n-type window layer 118, an n-type emitter layer 117, a p-type base layer 116 and a p-type BSF layer 115 having similar lattice constants are stacked in this order by MOCVD.

A tunnel junction layer 114 is stacked on the p-type BSF layer 115 by MOCVD, and then, on the tunnel junction layer 114, an n A window layer 113, an n-emitter layer 112, a p-type base layer 111 and a p-type BSF layer 110 are laminated in this order by MOCVD. The lattice constant of the p-type base layer 111 at this time is approximately the same as the lattice constant of the Ge substrate 201 .

A tunnel junction layer 109 is stacked on the p-type BSF layer 110 by MOCVD, and then, on the tunnel junction layer 109, an n A window layer 107, an n-type emitter layer 106, a p-type base layer 105 and a p-type BSF layer 104 are stacked in this order by MOCVD. Further, a buffer layer 199 and a p-type contact layer 103 are laminated in this order on the p-type BSF layer 104 by MOCVD.

The p-type contact layer 103 is made of p-type GaAs, for example. Also, the buffer layer 199 is made of, for example, p-type AlInAs. The p-type contact layer 103 and the p-type BSF layer 104 have different lattice constants. Moreover, the lattice constant of the buffer layer 199 is closer to the lattice constant of the p-type BSF layer 104 than the lattice constant of the p-type contact layer 103 at least on the p-type BSF layer 104 side.

In this embodiment, of the lattice constant of the buffer layer 199 , at least the portion in contact with the p-type BSF layer 104 has the same or approximately the same lattice constant as the p-type BSF layer 104 . Further, among the lattice constants of the buffer layer 199 , at least the portion in contact with the p-type contact layer 103 has a value equal to or approximately the same as the lattice constant of the p-type contact layer 103 .

Next, as shown in FIG. 7, the support substrate 101 is attached onto the p-type contact layer 103 with the metal layer 102 .

Next, as shown in FIG. 8, after etching the Ge substrate 201 with an alkaline aqueous solution, the etching stop layer 123 is etched with an acid aqueous solution.

Next, part of the contact layer 119 made of n-type GaAs is removed, and a metal layer 121 and an antireflection film 120 are formed.

Since the description of the third embodiment other than the above is the same as that of the first embodiment, the description thereof will be omitted.

<Embodiment 4>
FIG. 9 shows a schematic cross-sectional view of the III-V group compound semiconductor solar cell of Embodiment 4. As shown in FIG. In the III-V group compound semiconductor solar cell of Embodiment 4, the metal layer 1021 connected to the metal layer 102, which is the first electrode 102, is provided on the upper surface side (the side on which the second electrode 121 is provided). It is characterized by In other words, the group III-V compound semiconductor solar cell of Embodiment 4 is characterized in that the metal layer 1021 is provided on the side on which sunlight is incident. Since other configurations are the same as those of the III-V group compound semiconductor solar cells of Embodiments 2 and 3, description thereof is omitted.

In order to fabricate the III-V group compound semiconductor solar cell of Embodiment 4, first, according to Embodiment 3, metal layer 102, p-type contact layer 103, buffer layer 199, bottom cell 131 are formed on supporting substrate 101. , n-type buffer layer 108, tunnel junction layer 109, middle cell 132, tunnel junction layer 114, top cell 133, n-type contact layer 119, and metal layer 121 are fabricated.

Next, the structure is etched from the metal layer 121 side with an alkaline aqueous solution or an acid aqueous solution until the p-type contact layer 103 is exposed. In this embodiment, GaAs is used for the p-type contact layer 103 and AlInAs is used for the buffer layer 199 . Therefore, the buffer layer 199 is selectively etched with respect to the p-type contact layer 103 .

Next, on the exposed surface (upper surface) of the p-type contact layer 103, for example, a 30 nm-thick Au film and a 5000 nm-thick Ag film are successively vapor-deposited, followed by heat treatment to form a metal layer 1021. FIG.

Next, according to the third embodiment, an antireflection film 120 is formed. Thus, the III-V group compound semiconductor solar cell of Embodiment 4 is produced.

Descriptions of Embodiment 4 other than the above are the same as those of Embodiments 2 and 3, so descriptions thereof will be omitted.

<Embodiment 5>
FIG. 10(a) shows a schematic perspective view of the artificial satellite of Embodiment 5, and FIG. 10(b) shows a schematic plan view of the solar cell array of Embodiment 5 used in the artificial satellite of Embodiment 5. 10(c) shows a schematic plan view of the III-V group compound semiconductor solar cells of Embodiments 1 to 4 used in the solar cell array of Embodiment 5. FIG.

An artificial satellite 505 of Embodiment 5 shown in FIG. 10(a) has two III-V group compound semiconductor solar cells 501 and 502 on a substrate 503, which is, for example, a 4-inch substrate. form with Then, the group III-V compound semiconductor solar cells 501 and 502 of Embodiments 1 to 4 formed on the substrate 503 are separated into cells using, for example, dicing or laser. A bypass diode is attached to each of the III-V group compound semiconductor solar cells so that deterioration of the properties of one III-V group compound semiconductor solar cell does not lead to deterioration of the properties of the entire solar cell array 504 .

Then, the p-electrode and the n-electrode of the adjacent III-V group compound semiconductor solar cells are connected using an interconnector. As shown in FIG. 10(b), a solar cell array 504 is formed by attaching them to a plate called a paddle using an adhesive. By installing the solar cell array 504 as a power source of the satellite, the satellite 505 of Embodiment 5 shown in FIG. 10(a) can be produced.

Descriptions of Embodiment 5 other than the above are the same as those of Embodiments 1 to 4, and thus descriptions thereof are omitted.

Although the embodiments and examples have been described as above, it is planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

It should be considered that the embodiments and examples disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all changes within the meaning and scope equivalent to the scope of the claims.

101 support substrate, 102 metal layer, 103 contact layer, 199 buffer layer, 104 BSF layer, 105 base layer, 106 emitter layer, 107 window layer, 108 n-type buffer layer, 109 tunnel junction layer, 110 BSF layer, 111 base layer , 112 emitter layer, 113 window layer, 114 tunnel junction layer, 115 BSF layer, 116 base layer, 117 emitter layer, 118 window layer, 119 contact layer, 120 antireflection film, 121 metal layer, 122 GaAs substrate, 123 etching stop layer, 131 bottom cell, 132 middle cell, 133 top cell, 501, 502 group III-V compound semiconductor solar cell, 503 substrate, 504 solar cell array, 505 satellite

Claims (8)

a first electrode;
a contact layer provided on the first electrode and in direct contact with the first electrode;
a buffer layer provided on the contact layer and in direct contact with the contact layer;
a first cell containing a III-V compound semiconductor provided on the buffer layer;
a second electrode provided on the first cell;
has
the contact layer and the first cell have different lattice constants,
the lattice constant of the buffer layer is closer to the lattice constant of the first cell than the lattice constant of the contact layer at least on the first cell side;
A group III-V compound semiconductor solar cell , wherein a material constituting the buffer layer is any one of InGaP, AlInGaP, and AlInAs . 2. The group III-V compound semiconductor solar cell according to claim 1, wherein the lattice constant of said buffer layer is the same value as the lattice constant of said first cell at least on said first cell side. 3. The group III-V compound according to claim 1, wherein the lattice constant of the buffer layer is closer to the lattice constant of the contact layer than the lattice constant of the first cell on the contact layer side. semiconductor solar cell. 4. The group III-V compound semiconductor solar cell according to any one of claims 1 to 3, wherein the lattice constant of said buffer layer is the same value as the lattice constant of said contact layer on said contact layer side. 5. The group III-V compound semiconductor solar cell according to claim 1, wherein the lattice constant of said buffer layer changes continuously from said contact layer side to said first cell side. The group III-V compound semiconductor solar cell according to any one of claims 1 to 5, wherein the material constituting the contact layer is a material capable of transmitting light in the light wavelength region absorbed by the first cell. . a first electrode;
a contact layer provided on the first electrode;
a buffer layer provided on the contact layer;
a first cell containing a III-V compound semiconductor provided on the buffer layer;
a second cell containing a III-V compound semiconductor provided on the first cell;
a second electrode provided on the first cell;
has
the contact layer and the first cell have different lattice constants,
The lattice constant of the buffer layer is closer to the lattice constant of the first cell than the lattice constant of the contact layer at least on the first cell side, and the bandgap value of the material forming the contact layer is , a group III-V compound semiconductor solar cell that is equal to or greater than the bandgap value of the material that constitutes the second cell. An artificial satellite comprising the III-V group compound semiconductor solar cell according to any one of claims 1 to 7 .

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