CN212257428U

CN212257428U - Heterogeneous PN junction space battery epitaxial wafer

Info

Publication number: CN212257428U
Application number: CN202022495872.3U
Authority: CN
Inventors: 万智; 徐培强; 林晓珊; 张银桥; 王向武; 潘彬
Original assignee: Nanchang Kaijie Semiconductor Technology Co Ltd
Current assignee: Nanchang Kaijie Semiconductor Technology Co Ltd
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2020-12-29
Anticipated expiration: 2030-11-03

Abstract

The utility model discloses a heterogeneous PN junction space battery epitaxial wafer, belonging to the technical field of solar batteries, the key point of the technical proposal is that the device comprises a GaAs ohmic contact layer, a top battery, a GaInP/AlGaAs tunneling junction layer, a middle battery, a GaAs tunneling junction layer, a GaAs/GaInAs buffer layer and a bottom battery which are sequentially overlapped and combined together from top to bottom, the top battery comprises an AlInP window layer, a GaInP emitting region layer, a GaInP base region layer and an AlGaInP back surface field layer which are sequentially overlapped and combined from top to bottom, the middle battery comprises an AlInP window layer and a GaInAs emitting region layer, a GaInAs base region layer, an AlGaInAs back surface field layer and a GaInAs/AlGaInAs distributed Bragg reflector reflection layer which are sequentially overlapped and combined from top to bottom, the bottom battery comprises a GaInP emitting region layer, a GaInP nucleating layer and a Ge substrate which are sequentially overlapped and combined from top to bottom, and the bottom battery is of a heterogeneous Ge/GaInP PN junction structure. The heterojunction PN junction space cell epitaxial wafer can achieve higher photoelectric conversion efficiency while the manufacturing cost of the space solar cell epitaxial wafer is not remarkably increased.

Description

Heterogeneous PN junction space battery epitaxial wafer

Technical Field

The utility model relates to a solar cell technical field specifically is a heterogeneous PN junction space battery epitaxial wafer.

Background

The GaAs solar cell is a main power source of the current space vehicle, and compared with photovoltaic cells such as Si and CuInGaSe, the GaAs solar cell has the characteristics of high photoelectric conversion efficiency, good irradiation resistance, high temperature resistance and the like. The most commonly used structure of the space GaAs cell epitaxial wafer is a GaInP/GaInAs/Ge triple-junction solar cell structure (as shown in FIG. 1) with matched lattice parameters, which has the advantages of simple process and low cost, but because the energy gap combination of the lattice-matched GaInP/GaInAs/Ge triple-junction solar cell is 1.90/1.40/0.67 eV, the energy gap of the Ge bottom cell is small, the absorbed spectral range is wide, and the photo-generated current is far greater than that of the GaInAs middle cell and the GaInP top cell layer, in this way, the loss of the sunlight utilization rate is caused by the mismatch of the currents of the sub-cells, so the photoelectric conversion efficiency is low and can only reach about 30% (AM 0). At present, in order to improve the photoelectric conversion efficiency of the battery, battery structures such as flip chip, mismatch and multi-junction are presented, but the structures are not matched with the substrate Ge or GaAs, a thicker buffer layer is needed to eliminate stress, the defects of complex process, high manufacturing cost and the like are caused, and the wide application of the battery is limited. Therefore, obtaining higher photoelectric conversion efficiency without increasing the manufacturing cost of the space solar cell epitaxial wafer obviously is still one of the difficulties in the space cell industry at present.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a heterogeneous PN junction space battery epitaxial wafer, this kind of heterogeneous PN junction space battery epitaxial wafer has realized can also obtaining higher photoelectric conversion efficiency when not showing increase space solar cell epitaxial wafer manufacturing cost significantly.

The utility model discloses specifically adopt following technical scheme: the utility model provides a heterogeneous PN junction space battery epitaxial wafer, includes from last to stacking the GaAs ohmic contact layer, top battery, GaInP/AlGaAs tunnel junction layer, well battery, GaAs tunnel junction layer, GaAs/GaInAs buffer layer and the end battery that the combination is in the same place in proper order down, wherein the top battery includes from last to stacking the AlInP window layer, GaInP emitter region layer, GaInP base region layer and the AlGaInP back surface field layer that the combination is in the same place down in proper order, well battery includes from last to stacking the combination together AlInP window layer and GaInAs emitter region layer, GaInAs base region layer, AlGaInAs back surface field layer and GaInAs/AlGaInAs distributed Bragg reflector reflection layer down in proper order, end battery includes from last to stacking the combination together in proper order GaInP emitter region layer and GaInP nucleation layer and Ge substrate down, end battery is heterogeneous Ge/GaInP PN junction structure.

Further, in the bottom cell, the N-type material is GaInP.

To sum up, the utility model discloses following beneficial effect has:

this kind of heterogeneous PN junction space battery epitaxial wafer, improve the end battery PN junction into heterogeneous Ge/GaInP PN junction structure by the homogeneous PN junction of traditional Ge, and in end battery PN junction structure, N type material is GaInP, thereby can increase the open circuit voltage of end battery, the photoelectric conversion rate of battery has been promoted, in addition, the modified structure does not increase the manufacturing cost and the technology complexity of battery epitaxial wafer, be fit for extensive popularization, realized can also obtain higher photoelectric conversion efficiency when showing not to increase space solar cell epitaxial wafer manufacturing cost.

Drawings

FIG. 1 is a schematic diagram of a conventional lattice-matched triple-junction GaInP/GaInAs/Ge battery structure;

fig. 2 is the structural schematic diagram of the hetero PN junction triple-junction GaInP/GaInAs/Ge battery of the present invention.

In the figure: 1. a GaAs ohmic contact layer; 2. an AlInP window layer; 3. a GaInP emission region layer; 4. a GaInP base region layer; 5. an AlGaInP back surface field layer; 6. a GaInP/AlGaAs tunnel junction layer; 7. a GaInAs emitter layer; 8. a GaInAs base region layer; 9. AlGaInAs back surface field layer; 10. a GaInAs/AlGaInAs distributed Bragg reflector reflecting layer; 11. a GaAs tunnel junction layer; 12. a GaAs/GaInAs buffer layer; 13. an AlGaInP nucleation layer; 14. a Ge substrate; 15. a GaInP nucleation layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 2, a hetero PN junction space cell epitaxial wafer comprises a GaAs ohmic contact layer 1, a top cell, a GaInP/AlGaAs tunneling junction layer 6, a middle cell, a GaAs tunneling junction layer 11, a GaAs/GaInAs buffer layer 12 and a bottom cell which are sequentially stacked and combined together from top to bottom, wherein the top cell comprises an AlInP window layer 2, a GaInP emitter layer 3, a GaInP base layer 4 and an AlGaInP back surface field layer 5 which are sequentially stacked and combined together from top to bottom, the middle cell comprises an AlInP window layer 2, a GaInAs emitter layer 7, a GaInAs base layer 8, an AlGaInAs back surface field layer 9 and a GaInAs/algains distributed Bragg reflector reflection layer 10 which are sequentially stacked and combined together from top to bottom, the distributed Bragg reflector is abbreviated as dbr (distributed Bragg reflector), the bottom cell comprises a GaInP emitter layer 3, a GaInAs nucleation layer 15 and a Ge substrate 14 which are sequentially stacked and combined together from top to bottom, the bottom cell is a heterogeneous Ge/GaInP PN junction structure and in the bottom cell, the N-type material is GaInP.

The photoelectric conversion efficiency of the traditional GaInP/GaInAs/Ge three-junction solar cell is related to open-circuit voltage, short-circuit current and filling factor. The lattice-matched GaInP/GaInAs/Ge battery structure has the advantages that the energy gap of the Ge bottom battery is lower and is only about 0.67 eV, and more light energy is absorbed by the bottom battery, so that the current mismatch between the middle battery and the top battery is caused, and the photoelectric conversion efficiency of the middle battery and the top battery is influenced. In order to improve the photoelectric conversion efficiency of the battery, one approach is to improve the short-circuit current of the battery, namely, increase the current of the middle battery and the current of the top battery, and reduce the current of the bottom battery, so that the currents are more matched, and the utilization rate of solar energy is improved, such as mismatch, inversion and other structures; the other approach is to increase the open-circuit voltage of the battery, and adopt methods such as optimizing the energy gap combination of each sub-battery or increasing the number of battery junctions, such as disordered top batteries and four-junction battery structures. In the mismatch, flip-chip or other battery structure in the first approach, due to lattice mismatch between the substrate and the epitaxial layer, a thicker buffer layer is required to reduce dislocation of the mismatch, flip-chip or other structure, thereby increasing the manufacturing cost of the battery epitaxial wafer. Therefore, the utility model discloses a be that the second way: the open circuit voltage of the battery is improved.

The open-circuit voltage of the three-junction GaInP/GaInAs/Ge battery is the sum of the open-circuit voltage values of the sub-batteries. Increasing the open circuit voltage of any one subcell can raise the overall open circuit voltage of the cell. The open-circuit voltage is positively correlated with the potential difference of the built-in electric field of each sub-battery, the larger the built-in potential difference is, the stronger the built-in electric field intensity is, the higher the collection efficiency of photon-generated carriers is, the smaller the carrier recombination is, and the larger the open-circuit voltage of the battery is. The built-in potential difference is related to the forbidden band width, the electron affinity, the doping activation energy and the like of the PN junction material of the battery. For an N pole material of a PN junction battery, the smaller the electron affinity and the doping activation energy are, the larger the forbidden band width is, and the larger the built-in potential difference of the PN junction is. Because the short-circuit current of the middle battery and the short-circuit current of the top battery are far lower than that of the bottom battery, if the open-circuit voltage of the middle battery or the top battery is increased, the wave band of sunlight absorbed by the middle battery or the top battery is narrower, and therefore the more serious current mismatching problem is caused and is not paid.

It can be known to compare fig. 1 and fig. 2, the utility model discloses on lattice matching's GaInP/GaInAs/Ge three-junction solar cell basis, with end battery design for heterogeneous Ge/GaInP PN junction structure (being about to AlGaInP nucleation layer 13 has replaced GaInP emission zone layer 3 and GaInP nucleation layer 15), compare in the homogeneous Ge PN junction structure of improvement preceding end battery, increased end battery's open circuit voltage, promoted the whole photoelectric efficiency of battery. In the heterogeneous Ge/GaInP PN junction, the N-type material is GaInP doped Si, compared with the Ge doped P material before improvement, the electron affinity and the doping activation energy are smaller, the forbidden bandwidth is larger, and therefore the open-circuit voltage of the bottom cell can be obviously increased. After improvement, the bottom battery is of a heterojunction structure, and meanwhile, N-type materials are deposited on the substrate, so that more lattice defects can be caused, the short-circuit current of the bottom battery is further influenced, but the emitter region layer material with better lattice quality is obtained by optimizing the growth condition of the N-type materials of the bottom battery, and the whole short-circuit current of the battery cannot be influenced by the composition of a small amount of photon-generated carriers due to the fact that the current of the bottom battery is excessive. Therefore, the open-circuit voltage of the bottom battery is improved after improvement, and the whole short-circuit current is unchanged, so that higher photoelectric conversion efficiency can be obtained. In addition, this utility model simple process, manufacturing cost do not increase, are fit for large-scale popularization.

The utility model relates to a heterogeneous PN junction space battery epitaxial wafer adopts Metal Organic Chemical Vapor Deposition (MOCVD) mode deposit battery epitaxial layer. The substrate is P-type Ge-doped Ga with the doping concentration of 7E 17-2E 18cm^-3. MO sources are TMGa, TMIn and TMAl, and doping sources are DEZn and CCl₄And SiH₄Specific qi is PH₃And AsH₃。

The preparation method comprises the following specific steps:

A. heating the MOCVD reaction chamber, depositing a GaInP nucleating layer 15 with the thickness of 0.01-0.03 mu m, and doping SiH₄The source and doping concentration is 1-3 × 10¹⁸cm^-3；

B. Depositing a GaInP emitting region layer 3 on the substrate, wherein the deposition temperature is 620 ℃, the deposition thickness is 0.05-0.15 mu m, the deposition rate is 0.8-1 um/h, the ratio of VIII to V is 30-40, and SiH is doped₄Source and doping concentration 5X 10¹⁷～1×10¹⁸cm^-3；

C. A GaAs/GaInAs buffer layer 12 is deposited on the substrate with a thickness of 0.5-1.5 μm and doped with SiH₄The source and doping concentration is more than or equal to 1 x 10¹⁸cm^-3；

D. A GaAs tunnel junction layer 11 is deposited thereon, and the deposition thickness of the n-type GaAs layer is 0.01-0.03 μm, doped with SiH₄The source and doping concentration is more than or equal to 5 multiplied by 10¹⁸cm^-3(ii) a The deposition thickness of the p-type GaAs layer is 0.01-0.03 mu m, and CCl is doped₄The source and doping concentration is more than or equal to 2 x 10¹⁹cm^-3；

E. Depositing GaInAs/AlGaInAs Distributed Bragg Reflector (DBR) reflective layer 10 on the substrate, the thickness of the deposited layer is 1.0-2.0 μm, the doped DEZn source is adopted, and the doping concentration is 5-9 multiplied by 10¹⁷cm^-3；

F. Depositing AlGaInAs back surface field layer 9 with a thickness of 0.05-0.15 μm, doped with DEZn source and a doping concentration of 3-9 × 10¹⁷cm^-3；

G. Depositing a GaInAs base region layer 8 on the substrate, wherein the deposition thickness is 1-2 mu m, the doping concentration is 1-8 multiplied by 10, and the doping source is DEZn source¹⁶cm^-3；

H. Depositing a GaInAs emitting region layer 7 on the substrate, wherein the deposition thickness is 0.05-0.15 μm, and doping SiH₄The source and doping concentration is 1-2 x 10¹⁸cm^-3；

I. Depositing an AlInP window layer 2 with a thickness of 0.05-0.1 μm and doped with SiH₄The source and doping concentration is more than or equal to 1 x 10¹⁸cm^-3；

J. Depositing GaInP/AlGaAs tunnel junction layer 6 on the substrate, depositing n-type GaInP layer with thickness of 0.01-0.03 μm, doping SiH₄The source and doping concentration is more than or equal to 5 multiplied by 10¹⁸cm^-3. P-type AlGaAs layer with a deposition thickness of 0.01-0.03 μm doped with CCl₄The source and doping concentration is more than or equal to 2 x 10¹⁹cm^-3；

K. Depositing AlGaInP back surface field layer 5 with a thickness of 0.07-0.15 μm, doped with DEZn source and a doping concentration of 1-5 × 10¹⁸cm^-3；

L, depositing a GaInP base region layer 4 on the substrate, wherein the deposition thickness is 0.5-1.0 mu m, the DEZn source is doped, and the doping concentration is 1-8 multiplied by 10¹⁶cm^-3；

M, depositing a GaInP emitting region layer 3 on the substrate, wherein the deposition thickness is 0.06-0.15 μ M, and the doping source is SiH₄The doping concentration is 1 to 3 x 10¹⁸cm^-3；

N, depositing an AlInP window layer 2 on the substrate, wherein the deposition thickness is 0.06-0.15 mu m, and doping SiH₄The source and doping concentration is more than or equal to 1 x 10¹⁸cm^-3；

A GaAs ohmic contact layer 1 is deposited on the substrate with a thickness of 0.6-1 μm and doped with SiH₄The source and doping concentration is more than or equal to 3 multiplied by 10¹⁸cm^-3。

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications to the present embodiment without inventive contribution as required after reading the present specification, but all of them are protected by patent laws within the scope of the claims of the present invention.

Claims

1. The utility model provides a heterogeneous PN junction space battery epitaxial wafer, includes from last to stacking in proper order GaAs ohmic contact layer (1), top battery, GaInP/AlGaAs tunnel junction layer (6), well battery, GaAs tunnel junction layer (11), GaAs/GaInAs buffer layer (12) and end battery together down, wherein the top battery includes from last to stacking in proper order AlInP window layer (2), GaInP emission zone layer (3), GaInP base region layer (4) and AlGaInP back surface field layer (5) together down, well battery includes from last to stacking in proper order combined together down AlInP window layer (2) and GaInAs emission zone layer (7), GaInAs base region layer (8), AlGaInAs back surface field layer (9) and GaInAs/AlGaInAs distributed Bragg reflector reflection stratum (10), its characterized in that: the bottom cell comprises a GaInP emitting region layer (3), a GaInP nucleating layer (15) and a Ge substrate (14) which are sequentially overlapped and combined together from top to bottom, and the bottom cell is of a heterogeneous Ge/GaInP PN junction structure.

2. A hetero PN junction space cell epitaxial wafer as claimed in claim 1, wherein: in the bottom cell, the N-type material is GaInP.