Germanium-based anti-radiation three-junction solar cell
By designing a periodic lattice gradient buffer layer and reducing its thickness in germanium-based gallium arsenide solar cells, the composition and thickness were optimized, solving the radiation decay problem of As-based intermediate cells and P-based top cells, improving photoelectric conversion efficiency and radiation resistance, and extending cell life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-04-07
AI Technical Summary
In existing germanium-based triple-junction solar cells, the irradiation decay problem of As-based intermediate cells and P-based top cells is severe, which limits the radiation resistance of the cells, especially under high-energy particle irradiation, affecting the lifespan and efficiency of the cells.
A germanium-based gallium arsenide solar cell structure with a periodic lattice gradient buffer layer and reduced thickness was designed, including a germanium substrate, a GaInP nucleation layer, a GaInAs buffer layer, a periodic lattice gradient buffer layer, and a U-shaped bandgap subcell. By adjusting the composition and thickness, photon reflection and stress modulation were optimized to improve photoelectric conversion efficiency and radiation resistance.
It improves the photoelectric conversion efficiency of solar cells and enhances the radiation resistance of As-based intermediate cells and P-based top cells, thus extending the lifespan of the cells.
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Figure CN121815751A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solar cells, specifically relating to a germanium-based radiation-resistant triple-junction solar cell. Background Technology
[0002] Germanium-based triple-junction gallium arsenide solar cells possess advantages such as high photoelectric conversion efficiency and strong resistance to high-energy particle radiation, effectively improving satellite payload capacity and on-orbit lifespan in space applications. Currently, typical germanium-based triple-junction solar cell products have an efficiency of 32% (AM0, 25℃) and a total flux of 1E15 e / cm². 2 The efficiency degradation after 1 MeV electron irradiation is ≤18%, which can meet the 15-year on-orbit lifespan requirement of geostationary satellites. Currently, in triple-junction gallium arsenide solar cells, P-type, As-type, and germanium sub-cells have different radiation resistance capabilities. To achieve the highest possible conversion efficiency at the end of the solar cell's service life, the ultimate goal of sub-cell performance matching is to ensure that the current of each sub-cell is consistent at the end of its lifespan. In GaInP / Ga(In)As / Ge triple-junction solar cells, the radiation degradation of the As-type middle cell is greater than that of the GaInP top cell, which is the bottleneck limiting the cell's radiation resistance performance. Therefore, when designing the cell structure, it is necessary to intentionally make the initial current of the As-type middle cell slightly higher than that of the P-type top cell. In addition, to reduce the radiation degradation of the Ga(In)As sub-cell, the thickness of the Ga(In)As sub-cell can be reduced, and a distributed Bragg reflector (DBR) can be fabricated on its back field layer during epitaxial growth to solve the problem of reduced photon absorption capacity caused by thinning the absorption layer. Through the above optimizations, the radiation resistance of triple-junction solar cells can meet the 15-year on-orbit lifespan requirement of geostationary satellites.
[0003] Although As compound subcells exhibit the most severe degradation after irradiation, the irradiation degradation of P compound top cells should not be ignored, especially under higher flux irradiation. Furthermore, the high density of mismatched defects in P compound materials leads to a decrease in their radiation resistance. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a germanium-based radiation-resistant triple-junction solar cell, and to design a periodic structure lattice gradient buffer layer for the As-based intermediate cell and the P-based top cell while reducing the thickness, thereby improving the photoelectric conversion efficiency of the solar cell and improving its radiation resistance.
[0005] The technical solution adopted in this invention is: a germanium-based gallium arsenide solar cell, comprising, from bottom to top: a germanium substrate, a GaInP nucleation layer, a GaInAs buffer layer, a first tunnel junction, and (AlGa). 1-a In a As / Ga1-a In a As periodic lattice gradient buffer layer, (AlGa) 1-b In b As / Ga 1-b In b As periodic structure overshoot layer, U-shaped bandgap (AlGa) 1-c In c As subcell, second tunnel junction, (AlGa) 1-d In d As / Ga 1-d In d As a second-period lattice graded layer, (AlGa) 1-e In e As / Ga 1-e In e As second-period structure overpass layer, U-shaped bandgap (AlGa) 1-f In f P-cells, Ga 1-g In g As cap layer; The (AlGa) 1-a In a As / Ga 1-a In a The In composition of the As periodic structure lattice gradient buffer layer is gradually changed from 0 to c, that is, its lattice constant gradually changes from matching the germanium substrate to matching the U-shaped bandgap (AlGa). 1- c In c As a sub-cell; at the same time, the number of cycles in this structure ranges from 2 to 60, serving to reflect and transmit through the U-shaped bandgap (AlGa). 1- c In c The effect of photons on the As sub-cell, in each cycle (AlGa) 1-a In a As thickness is 2nm-300nm, Ga 1-a In a The thickness of As is 2nm-300nm; The (AlGa) 1-b In b As / Ga 1-b In b The In content of the As periodic structure overpass layer is greater than that of the (AlGa) with the U-shaped bandgap. 1- c In cThe In composition of the As sub-cell, i.e., b≥c, plays a role in stress regulation; at the same time, the number of periods in this structure ranges from 2 to 60, which serves to reflect and transmit the U-shaped bandgap (AlGa). 1-c In c The effect of photons on the As sub-cell, in each cycle (AlGa) 1- b In b As thickness is 2nm-300nm, Ga 1-b In b The thickness of As is 2nm-300nm; The U-shaped bandgap (AlGa) 1-c In c As sub-cells include p-type doped (AlGa). 1-c In c The system consists of an As base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where (AlGa) 1-c In c As-based layer: 0 < c ≤ 0.5, thickness 30nm-5000nm, and by adjusting the composition ratio of Al and Ga to achieve (AlGa). 1-c In c The bandgap of As gradually decreases; the unintentionally doped i-layer is (AlGa). 1-c In c As or Ga 1-x In x P material, 0.4≤x<1, thickness 10nm-1000nm; emitter layer is Ga 1- x In x P material, 0.4≤x<1, thickness 30nm-5000nm.
[0006] The (AlGa) 1-d In d As / Ga 1-d In d The In composition of the second-period lattice gradient layer of As is gradually varied, with a range of c≥d≥0, meaning its lattice constant varies from the U-shaped bandgap (AlGa). 1-c In c As sub-cell matching gradually changes to (AlGa) with the U-shaped bandgap. 1-f In f P-subcell matching; simultaneously, each gradient change is achieved by (AlGa). 1-d In d As / Ga 1-d In d As a periodic structure, with the number of periods ranging from 2 to 60, it serves to reflect and transmit (AlGa).1-f In f The effect of photons in a P-cell, in each cycle (AlGa) 1-d In d As thickness is 2nm-300nm, Ga 1-d In d The thickness of As is 2nm-300nm; The (AlGa) 1-e In e As / Ga 1-e In e The lattice constant of the overshoot layer in the second-period As structure is no greater than that of (AlGa). 1- f In f The lattice constant of the p-cell plays a role in stress regulation; simultaneously, the number of periods in this structure ranges from 2 to 60, serving as a reflector and transmitter (AlGa). 1-f In f The effect of photons in a P-cell, in each cycle (AlGa) 1-e In e As thickness is 2nm-300nm, Ga 1-e In e The thickness of As is 2nm-300nm; The U-shaped bandgap (AlGa) 1-f In f A p-type cell consists of a p-type doped base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where 0.4 ≤ f < 1, and a thickness of 30 nm–5000 nm. The composition ratio of Al and Ga is adjusted to achieve (AlGa). 1-f In f The bandgap of P gradually decreases; the thickness of the unintentionally doped i-layer is 10nm-1000nm; the thickness of the emitter layer is 30nm-5000nm, and the composition ratio of Al and Ga is adjusted to achieve (AlGa). 1-f In f The band gap of P gradually increases, making the entire (AlGa) band gap... 1-f In f The bandgap variation of the P-sub-cell is such that the i-layer in the middle has the smallest bandgap; The cap layer is n-type doped Ga. 1-g In g As, where 0 < g ≤ 0.5, and the thickness range is 50 nm - 500 nm.
[0007] Furthermore, the germanium substrate and Ga 1-g In g The As cap layer is provided with a lower electrode and an upper electrode respectively.
[0008] Furthermore, the U-shaped bandgap (AlGa) 1-c In c In As sub-cells, (AlGa) 1-c In c The doping concentration of the As base layer is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
[0009] Furthermore, the U-shaped bandgap (AlGa) 1-c In c In As sub-cells, Ga 1-x In x The doping concentration of the P-emitter layer material is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
[0010] Furthermore, the U-shaped bandgap (AlGa) 1-f In f The base layer doping concentration of the P-sub cell is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
[0011] Furthermore, the U-shaped bandgap (AlGa) 1-f In f The emitter layer doping concentration of the P-sub cell is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
[0012] Furthermore, the Ga 1-g In g The doping concentration of the As cap layer is 1×10⁻⁶. 18 -1×10 21 cm -3 .
[0013] Compared with existing technologies, this invention has the following advantages and beneficial effects: This invention simultaneously designs a periodic lattice gradient buffer layer for both the As-bide intermediate cell and the P-bide top cell, while also reducing its thickness. This improves both the photoelectric conversion efficiency and radiation resistance of the solar cell. Furthermore, the U-shaped bandgap design for both the As-bide intermediate cell and the P-bide top cell increases the drift motion of photogenerated carriers in the sub-cells, weakens the impact of irradiation-induced defects on the diffusion length of photogenerated carriers, and further enhances the radiation resistance of the solar cell. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the germanium-based radiation-resistant triple-junction solar cell of the present invention. Detailed Implementation
[0015] To further understand the invention's content, features, and effects, the following embodiments are provided, but the implementation of the invention is not limited thereto. A detailed description follows: This embodiment is a germanium-based gallium arsenide solar cell, including the following steps: like Figure 1 The diagram shows a schematic of the germanium-based gallium arsenide solar cell of the present invention. A GaInP nucleation layer, a GaInAs buffer layer, a first tunnel junction, and (AlGa) are sequentially grown on a P-type germanium substrate using MOCVD technology. 1-a In a As / Ga 1-a In a As periodic lattice gradient buffer layer, (AlGa) 1-b In b As / Ga 1-b In b As periodic structure overshoot layer, U-shaped bandgap (AlGa) 1-c In c As subcell, second tunnel junction, (AlGa) 1-d In d As / Ga 1-d In d As a second-period lattice graded layer, (AlGa) 1-e In e As / Ga 1-e In e As second-period structure overpass layer, U-shaped bandgap (AlGa) 1-f In f P-cells, Ga 1-g In g As cap layer.
[0016] The GaInP nucleation layer has Si or Se as its n-type dopant, a growth temperature of 450–700℃, and a thickness range of 20–500 nm. An n-type Ge layer is formed by the diffusion of phosphorus atoms in the nucleation layer, which together with the p-type germanium substrate constitutes a germanium cell.
[0017] The GaInAs buffer layer has an n-type dopant of Si or Se, a growth temperature of 500–750℃, and a thickness range of 100–2000 nm.
[0018] The first tunnel junction comprises an n-type doped GaAs layer and a p-type doped AlGaAs layer, wherein the GaAs layer is doped with Se or Te at a doping concentration of 1 × 10⁻⁶.19 -1×10 21 cm -3 The thickness ranges from 5 nm to 50 nm, and the growth temperature is 450–700℃; the dopant of the AlGaAs layer is Zn or C, and the doping concentration is 1×10⁻⁶. 19 -1×10 21 cm -3 The thickness ranges from 5nm to 50nm, and the growth temperature is 450–700℃.
[0019] (AlGa) 1-a In a As / Ga 1-a In a The In composition of the As periodic lattice gradient buffer layer gradually changes from 0 to c-p type doping, with a doping concentration of 1×10⁻⁶. 17 cm -3 -1×10 19 cm -3 The growth temperature is 600–750℃, achieving a lattice constant that gradually changes from matching the germanium substrate to matching the U-shaped bandgap (AlGa). 1-c In c As sub-cell matching. Meanwhile, the number of cycles in this structure ranges from 2 to 60, with each cycle containing (AlGa). 1-a In a As thickness is 2nm-300nm, Ga 1-a In a As thickness is 2nm-300nm, allowing Ga to be reflected and transmitted. 1-c In c As the photons of the sub-cell are absorbed by the sub-cell, thereby improving the quantum efficiency and radiation resistance of the sub-cell.
[0020] (AlGa) 1-b In b As / Ga 1-b In b As the first-period overpass layer, the doping concentration is 1×10⁻⁶. 17 -1×10 19 cm -3 The growth temperature is 600–750℃, and its In content is greater than that of (AlGa) with a U-shaped band gap. 1-c In c The In composition of the As sub-cell, i.e., b≥c, plays a role in stress regulation. Meanwhile, the number of periods in this structure ranges from 2 to 60, with each period containing (AlGa). 1-b In b As thickness ranges from 5nm to 300nm, Ga 1-b Inb As with a thickness of 5nm-300nm can reflect light that passes through the U-shaped bandgap (AlGa). 1-c In c As the photons of the sub-cell are absorbed by the sub-cell, thereby improving the quantum efficiency and radiation resistance of the sub-cell.
[0021] U-shaped bandgap (AlGa) 1-c In c As sub-cells include p-type doped (AlGa). 1-c In c The system consists of an As base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where (AlGa) 1-c In c As-based layer: 0 < c ≤ 0.5, doping concentration 1 × 10⁻⁶ 16 cm -3 -1×10 19 cm -3 The thickness is 30nm-5000nm, and the ratio of Al and Ga components is adjusted to make (AlGa). 1-c In c The band gap of As gradually decreases, such as from bottom to top (AlGa). 1-c In c The composition of As changes from (Al) 0.2 Ga 0.8 ) 1-c In c As gradually transforms into Ga 1-c In c As; the unintentionally doped i-layer can be Ga 1-c In c As or Ga 1-x In x P material, 0.4≤x<1, thickness 10nm-1000nm; emitter layer can be Ga 1-x In x P material, 0.4≤x<1, doping concentration 1×10 16 cm -3 -1×10 19 cm -3 Thickness 30nm-5000nm.
[0022] The second tunnel junction comprises an n-type doped AlGaInP layer and a p-type doped AlGaInAs layer, wherein the dopant of the AlGaInP layer is Se or Te, and the doping concentration is 1×10⁻⁶. 19 -1×10 21 cm -3The thickness ranges from 5 nm to 50 nm, and the growth temperature is 450–700℃; the dopant of the AlGaInAs layer is Zn or C, and the doping concentration is 1×10⁻⁶. 19 -1×10 21 cm -3 The thickness ranges from 5nm to 50nm, and the growth temperature is 450–700℃.
[0023] (AlGa) 1-d In d As / Ga 1-d In d The In composition of the second-period lattice gradient layer of As is gradually varied, with a range of c≥d≥0, meaning its lattice constant varies from the U-shaped bandgap (AlGa). 1-c In c As sub-cell matching gradually changes to (AlGa) with the U-shaped bandgap. 1-f In f P-sub-cell. Simultaneously, each gradient change is achieved by (AlGa). 1-d In d As / Ga 1- d In d The structure consists of a periodic As bandgap, with the number of periods ranging from 2 to 60, which serves to reflect and transmit the U-shaped bandgap (AlGa). 1-f In f The effect of photons on P-cells.
[0024] (AlGa) 1-e In e As / Ga 1-e In e As second-period overpass layer, grown at temperatures of 600–750℃, has a lattice constant no greater than (AlGa). 1-f In f The lattice constant of the p-cell plays a role in stress regulation. Simultaneously, the number of periods in this structure ranges from 2 to 20, serving to reflect and transmit through the U-shaped bandgap (AlGa). 1-f In f The effect of photons in a P-cell, in each cycle (AlGa) 1-e In e As thickness is 2nm-300nm, Ga 1-e In e The thickness of As is 2nm-300nm.
[0025] U-shaped bandgap (AlGa) 1-f In fA p-type sub-cell consists of a p-type doped base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where 0.4 ≤ f < 1, and the base layer doping concentration is 1 × 10⁻⁶. 16 cm -3 -1×10 19 cm -3 The thickness ranges from 30nm to 5000nm, and the ratio of Al to Ga components is adjusted to achieve (AlGa). 1-f In f The band gap of P gradually decreases, as shown from bottom to top (AlGa). 1-f In f The composition of P changes from (Al) 0.2 Ga 0.8 ) 1-f In f P gradually transforms into Ga 1-f In f P; unintentionally doped i-layer thickness 10nm-1000nm; emitter layer doping concentration 1×10⁻⁶ 16 cm -3 -1×10 19 cm -3 The thickness ranges from 30nm to 5000nm, and the ratio of Al to Ga components is adjusted to achieve (AlGa). 1-f In f The band gap of P gradually increases, such as from bottom to top (AlGa). 1-f In f The composition of P changes from Ga 1-f In f P gradually becomes (Al) 0.2 Ga 0.8 ) 1-f In f P, making the entire (AlGa) 1-f In f The bandgap variation of the P-sub-cell is such that the i-layer in the middle has the smallest bandgap.
[0026] Ga 1-g In g The As cap layer is n-type doped, where 0 < g ≤ 0.5, and the doping concentration is 1 × 10⁻⁶. 18 -1×10 21 cm -3 The thickness ranges from 50nm to 500nm.
[0027] After the above structure is prepared by epitaxy, the upper and lower metal electrodes and antireflective film of the battery are prepared according to known battery device processes.
[0028] By implementing the above steps, the preparation process of a germanium-based gallium arsenide solar cell of the present invention is completed.
[0029] The above embodiments are one implementation of the present invention, but the implementation of the present invention is not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A germanium-based gallium arsenide solar cell, characterized in that, From bottom to top, the layers consist of: a germanium substrate, a GaInP nucleation layer, a GaInAs buffer layer, a first tunnel junction, and (AlGa). 1-a In a As / Ga 1-a In a As periodic lattice gradient buffer layer, (AlGa) 1- b In b As / Ga 1-b In b As periodic structure overshoot layer, U-shaped bandgap (AlGa) 1-c In c As subcell, second tunnel junction, (AlGa) 1-d In d As / Ga 1-d In d As a second-period lattice graded layer, (AlGa) 1-e In e As / Ga 1-e In e As second-period structure overpass layer, U-shaped bandgap (AlGa) 1-f In f P-cells, Ga 1-g In g As cap layer; The (AlGa) 1-a In a As / Ga 1-a In a The In composition of the As periodic structure lattice gradient buffer layer is gradually changed from 0 to c, that is, its lattice constant gradually changes from matching the germanium substrate to matching the U-shaped bandgap (AlGa). 1-c In c As a sub-cell; at the same time, the number of cycles in this structure ranges from 2 to 60, serving to reflect and transmit through the U-shaped bandgap (AlGa). 1-c In c The effect of photons on the As sub-cell, in each cycle (AlGa) 1-a In a As thickness is 2nm-300nm, Ga 1-a In a The thickness of As is 2nm-300nm; The (AlGa) 1-b In b As / Ga 1-b In b The In content of the As periodic structure overpass layer is greater than that of the (AlGa) with the U-shaped bandgap. 1- c In c The In composition of the As sub-cell, i.e., b≥c, plays a role in stress regulation; at the same time, the number of periods in this structure ranges from 2 to 60, which serves to reflect and transmit the U-shaped bandgap (AlGa). 1-c In c The effect of photons on the As sub-cell, in each cycle (AlGa) 1- b In b As thickness is 2nm-300nm, Ga 1-b In b The thickness of As is 2nm-300nm; The U-shaped bandgap (AlGa) 1-c In c As sub-cells include p-type doped (AlGa). 1-c In c The system consists of an As base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where (AlGa) 1-c In c As-based layer: 0 < c ≤ 0.5, thickness 30nm-5000nm, and by adjusting the composition ratio of Al and Ga to achieve (AlGa). 1-c In c The bandgap of As gradually decreases; the unintentionally doped i-layer is (AlGa). 1-c In c As or Ga 1-x In x P material, 0.4≤x<1, thickness 10nm-1000nm; emitter layer is Ga 1-x In x P material, 0.4≤x<1, thickness 30nm-5000nm. The (AlGa) 1-d In d As / Ga 1-d In d The In composition of the second-period lattice gradient layer of As is gradually varied, with a range of c≥d≥0, meaning its lattice constant varies from the U-shaped bandgap (AlGa). 1-c In c As sub-cell matching gradually changes to (AlGa) with the U-shaped bandgap. 1-f In f P-subcell matching; simultaneously, each gradient change is achieved by (AlGa). 1-d In d As / Ga 1- d In d As a periodic structure, with the number of periods ranging from 2 to 60, it serves to reflect and transmit (AlGa). 1-f In f The effect of photons in a P-cell, in each cycle (AlGa) 1-d In d As thickness is 2nm-300nm, Ga 1-d In d The thickness of As is 2nm-300nm; The (AlGa) 1-e In e As / Ga 1-e In e The lattice constant of the overshoot layer in the second-period As structure is no greater than that of (AlGa). 1-f In f The lattice constant of the p-cell plays a role in stress regulation; simultaneously, the number of periods in this structure ranges from 2 to 60, serving as a reflector and transmitter (AlGa). 1-f In f The effect of photons in a P-cell, in each cycle (AlGa) 1-e In e As thickness is 2nm-300nm, Ga 1-e In e The thickness of As is 2nm-300nm; The U-shaped bandgap (AlGa) 1-f In f A p-type cell consists of a p-type doped base layer, an unintentionally doped i-layer, and an n-type doped emitter layer, where 0.4 ≤ f < 1, and a thickness of 30 nm–5000 nm. The composition ratio of Al and Ga is adjusted to achieve (AlGa). 1-f In f The bandgap of P gradually decreases; the thickness of the unintentionally doped i-layer is 10nm-1000nm; the thickness of the emitter layer is 30nm-5000nm, and the composition ratio of Al and Ga is adjusted to achieve (AlGa). 1-f In f The band gap of P gradually increases, making the entire (AlGa) band gap... 1-f In f The bandgap variation of the P-sub-cell is such that the i-layer in the middle has the smallest bandgap; The cap layer is n-type doped Ga. 1-g In g As, where 0 < g ≤ 0.5, and the thickness range is 50 nm - 500 nm.
2. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The germanium substrate and Ga 1-g In g The As cap layer is provided with a lower electrode and an upper electrode respectively.
3. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The U-shaped bandgap (AlGa) 1- c In c In As sub-cells, (AlGa) 1-c In c The doping concentration of the As base layer is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
4. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The U-shaped bandgap (AlGa) 1- c In c In As sub-cells, Ga 1-x In x The doping concentration of the P-emitter layer material is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
5. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The U-shaped bandgap (AlGa) 1-f In f The base layer doping concentration of the P-sub cell is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
6. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The U-shaped bandgap (AlGa) 1-f In f The emitter layer doping concentration of the P-sub cell is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .
7. The germanium-based gallium arsenide solar cell according to claim 1, characterized in that, The Ga 1-g In g The doping concentration of the As cap layer is 1×10⁻⁶. 18 -1×10 21 cm -3 .