A method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer

Abstract

The present invention discloses a method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer, which optimizes the back surface field layer in a conventional space lattice matching GaInP / GaInAs / Ge cell, that is, the present invention introduces a composite back surface field structure into the middle cell and the top cell in the space lattice matching GaInP / InGaAs / Ge cell, respectively, and the middle cell is Al 0.3 Ga 0.7 As / Ga 0.5 In 0.5 P composite back surface field structure, top cell is Al 0.33 Ga 0.15 In 0.52 P / Al 0.1 Ga 0.4 In 0.5 P composite back surface field structure. Through the design of the components and concentrations of each layer of the composite back surface field, a conduction band step and concentration gradient are formed in the back surface field, so that the electric field between the back surface field and the base is strengthened, so that the reflection efficiency of the photogenerated carriers generated in the base region of the battery is improved when they reach the back surface field, and the minority carriers are better collected, thereby improving the photoelectric conversion efficiency of the battery.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a battery epitaxial wafer, in particular to a method for manufacturing a composite back surface field space GaInP / GaInAs / Ge battery epitaxial wafer. Background Art

[0002] GaAs solar cells are the main power source for spacecraft. Compared with other photovoltaic cells, they have higher photoelectric conversion efficiency, stronger radiation resistance and better high temperature resistance. The most commonly used GaAs cell in space is the lattice-matched GaInP / GaInAs / Ge structure. Compared with other GaAs cell structures such as mismatched and flip-chip structures, this structure has simpler process and lower cost, but the disadvantage is that the photoelectric conversion efficiency is low, which can only reach about 30% at present.

[0003] In order to further improve the efficiency of spatial GaInP / GaInAs / Ge lattice-matched cells without significantly increasing the manufacturing cost of cell epitaxial wafers, improving the collection efficiency of photogenerated carriers in the cell is one way. Summary of the invention

[0004] The object of the present invention is to provide a method for optimizing the back surface field layer in a spatial GaInP / GaInAs / Ge cell structure and improving the photoelectric conversion efficiency of the cell.

[0005] The object of the present invention is achieved in this way: a method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer, wherein: a composite back surface field structure is added to the top cell and the middle cell structure respectively, and a stronger electric field is formed between the back surface field layer and the base layer through the concentration gradient and conduction band step formed by the composite back surface field, thereby improving the reflection of the back surface field on the minority carriers of photogenerated carriers, and at the same time improving the attraction of the majority carriers of photogenerated carriers, thereby improving the collection efficiency of the photogenerated carriers of the cell and improving the overall photoelectric conversion efficiency of the cell.

[0006] The specific steps are as follows:

[0007] Using MOCVD, n-AlGaInP nucleation layer, n-GaAs / n-GaInAs buffer layer, n++-GaAs / p++-GaAs tunneling junction layer, p-AlGaAs / p-AlGaInAs (DBR) reflective layer, p-AlGaAs / p-AlGaInAs (DBR) reflective layer, and p-AlGaAs / p-AlGaInAs (DBR) reflective layer are deposited on the p-Ge substrate in sequence. 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, p-GaInAs base layer, re-deposited n-GaInAs emitter layer, n-AlInP window layer, n++-GaInP / p++-AlGaAs tunneling junction layer, p-Al0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, p-GaInP base layer, re-deposited n-GaInP emitter layer, n-AlInP window layer and n+-GaAs ohmic contact layer.

[0008] The substrate material is p-type Ge substrate, the substrate is doped with Ga source, and the doping concentration is 0.2E18~3E18cm -3 , thickness is 130~150μm, (100) is off to 〈111〉9° cutting angle.

[0009] The thickness of the n-AlGaInP nucleation layer is 0.01 μm, and the doping concentration is 1 to 2×10 18 cm -3 .

[0010] The thickness of the n-GaAs / n-GaInAs buffer layer is 0.5 μm and the doping concentration is ≥1×10 18 cm -3 .

[0011] n++-GaAs / p++-GaAs tunneling junction layer, wherein the thickness of the n++-GaAs layer is 0.01 to 0.03 μm and the doping concentration is ≥5×10 18 cm -3 The thickness of the p++-GaAs layer is 0.01 to 0.03 μm, and the doping concentration is ≥1×10 19 cm -3 .

[0012] The thickness of the p-AlGaAs / p-AlGaInAs (DBR) reflective layer is 1.8 μm and the doping concentration is 5×10 17 cm -3 .

[0013] p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, in which Al 0.3 Ga 0.7 The As thickness is 0.02 μm and the doping concentration is 8×10 17 ~1.2×10 18 cm -3 , Ga 0.5 In 0.5 The P thickness is 0.1 μm and the doping concentration is 5×10 17 ~8×10 17 cm-3 .

[0014] The thickness of the p-GaInAs base layer is 2.1 μm, and the doping concentration is 2 to 8×10 16 cm -3 .

[0015] The thickness of the n-GaInAs emitter layer is 0.1 μm and the doping concentration is 1×10 18 cm -3 .

[0016] The n-AlInP window layer has a thickness of 0.1 μm and a doping concentration of 1×10 18 cm -3 .

[0017] n++-GaInP / p++-AlGaAs tunneling junction layer, where the thickness of the n++-GaInP layer is 0.01-0.03 μm and the doping concentration is ≥5×10 18 cm -3 The thickness of the p++-AlGaAs layer is 0.01 to 0.03 μm, and the doping concentration is ≥5×10 19 cm -3 .

[0018] p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, in which Al 0.33 Ga 0.15 In 0.52 The P thickness is 0.02 μm and the doping concentration is 1 to 2×10 18 cm -3 ,Al 0.1 Ga 0.4 In 0.5 The P thickness is 0.1 μm and the doping concentration is 5×10 17 ~1×10 18 cm -3 .

[0019] The thickness of the p-GaInP base layer is 0.9 μm, and the composition is Ga 0.49 In 0.51 P, doping concentration is 1~8×10 16 cm -3 .

[0020] The thickness of the n-GaInP emitter layer is 0.1 μm and the doping concentration is 1×10 18 cm -3 .

[0021] The n-AlInP window layer has a thickness of 0.1 μm and a doping concentration of 1×10 18 cm -3 .

[0022] The thickness of the n+-GaAs ohmic contact layer is 0.5 μm, and the doping concentration is greater than 5×10 18 cm -3 .

[0023] Compared with the conventional lattice-matched GaInP / GaInAs / Ge structure, this structure introduces Al in the middle cell and top cell respectively. 0.3 Ga 0.7 As / Ga 0.5 In 0.5 P and Al 0.33 Ga 0.15 In 0.52 P / Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer structure; by introducing the composite back surface field structure, a concentration gradient and conduction band step are formed between the back surface field layer and the base region, so that a stronger electric field is formed between the two, which improves the reflection of the back surface field on the minority photogenerated carriers, and at the same time increases the attraction to the majority photogenerated carriers, thereby improving the collection efficiency of the photogenerated carriers of the battery and improving the overall photoelectric conversion efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the epitaxial layer structure involved in the present invention.

[0025] Figure 2 It is a schematic diagram of the band gap structure of the middle battery, the top battery base layer, and the composite back surface field layer involved in the present invention.

[0026] The accompanying drawings are marked as follows:

[0027] 100: P-type Ge substrate; 101: n-AlGaInP nucleation layer;

[0028] 102: n-GaAs / n-GaInAs buffer layer; 103: n++-GaAs / p++-GaAs tunneling junction layer;

[0029] 104: p-AlGaAs / p-AlGaInAs (DBR) reflective layer;

[0030] 105: p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer;

[0031] 106: p-GaInAs base layer; 107: n-GaInAs emitter layer;

[0032] 108: n-AlInP window layer; 109: n++-GaInP / p++-AlGaAs tunneling junction layer;

[0033] 110: p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer;

[0034] 111: p-GaInP base layer; 112: n-GaInP emitter layer;

[0035] 113: n-AlInP window layer; 114: n+-GaAs ohmic contact layer. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to examples and accompanying drawings.

[0037] A method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer, the equipment used is 2600G3 MOCVD (metal organic chemical vapor deposition) produced by AXITRON of Germany. The substrate is a p-type Ge substrate, doped with Ga source, and the doping concentration is 0.2E18~3E18cm -3 , thickness is 130~150μm, (100) deviation <111> 9° crystal orientation angle. The MO sources used are TMGa, TMAl and TMIn, the doping sources used are CCl4, DEZn and SiH4, and the special gases used are AsH3 and PH3;

[0038] The specific steps are as follows:

[0039] A. PH3 is introduced into the MOCVD reaction chamber in advance, the temperature of the reaction chamber is raised to 690°C, the pressure is controlled to 230 mbar, and 1×10 18 cm -3 The reaction chamber is cooled to 620℃, and the source TMAl, TMGa, TMIn, and special gas PH3 are introduced to deposit the n-AlGaInP nucleation layer. The thickness of the n-AlGaInP nucleation layer is 0.01μm, and the SiH4 source is doped with a doping concentration of 1 to 2×10 18 cm -3 ;

[0040] B. The pressure was increased to 450 mbar, the temperature of the reaction chamber was increased to 650 °C, and an n-GaAs / n-GaInAs buffer layer was deposited on the n-AlGaInP nucleation layer. The thickness of the n-GaAs / n-GaInAs buffer layer was 0.5 μm, and the SiH4 source was doped with a doping concentration of ≥1×10 18 cm -3 ;

[0041] C. Reduce the pressure of the reaction chamber to 50 mbar, and deposit an n++-GaAs layer on the n-GaAs / n-GaInAs buffer layer at a temperature of 650°C, wherein the n++-GaAs layer is deposited to a thickness of 0.01-0.03 μm, and is doped with a SiH4 source with a doping concentration of ≥5×10 18 cm -3 , a p++-GaAs layer is deposited on the n++-GaAs layer at 620°C, the thickness of the p++-GaAs layer is 0.01-0.03 μm, and the CCl4 source is doped with a doping concentration of ≥1×10 19 cm -3 ;

[0042] D. Deposit a p-AlGaAs / p-AlGaInAs (DBR) reflective layer on the p++-GaAs layer at 650°C. The thickness of the p-AlGaAs / p-AlGaInAs reflective layer is 1.8 μm. It is doped with a DEZn source and has a doping concentration of 5 to 8×10 17 cm -3 ;

[0043] E. Deposit p-AlGaAs / p-AlGaInAs (DBR) reflective layer at 650°C. 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, first deposit Al 0.3 Ga 0.7 As layer, deposited with a thickness of 0.02 μm, doped with DEZn source, with a doping concentration of 8×10 17 ~1.2×10 18 cm -3 , and then deposited Ga 0.5 In 0.5 The P layer has a deposition thickness of 0.1 μm and is doped with a DEZn source at a doping concentration of 5×10 17 ~8×10 17 cm -3 ;

[0044] F. In p-Al 0.3 Ga 0.7 As / p-Ga0.5 In 0.5 The p-GaInAs base layer was deposited on the P composite back surface field layer at 650°C with a deposition thickness of 2.1 μm and doped with DEZn source with a doping concentration of 2 to 8×10 16 cm -3 ;

[0045] G. Deposit an n-GaInAs emitter layer on the p-GaInAs base layer at 650°C. The thickness of the n-GaInAs emitter layer is 0.1 μm and the doping concentration is 1×10 18 cm -3 ;

[0046] H. Deposit an n-AlInP window layer on the n-GaInAs emitter layer at 650°C. The n-AlInP window layer is deposited to a thickness of 0.1 μm and doped with SiH4 source at a doping concentration of 1×10 18 cm -3 ;

[0047] I. Deposit an n++-GaInP / p++-AlGaAs tunneling junction layer on the n-AlInP window layer at 620°C, wherein the n++-GaInP layer is deposited to a thickness of 0.01-0.03 μm and doped with a SiH4 source at a doping concentration of ≥5×10 18 cm -3 The thickness of the p++-AlGaAs layer is 0.01-0.03 μm, and the doping concentration is ≥5×10 19 cm -3 ;

[0048] J. Deposit p-Al on the n++-GaInP / p++-AlGaAs tunneling junction layer at 620°C 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, first deposit Al 0.33 Ga 0.15 In 0.52 The P layer has a deposition thickness of 0.02 μm and is doped with a DEZn source at a doping concentration of 1 to 2×10 18 cm -3 . Re-deposition of Al 0.1 Ga 0.4 In 0.5 P layer, deposited with a thickness of 0.1 μm, doped with DEZn source and a doping concentration of 5×10 17 ~1×10 18 cm -3 ;

[0049] K, in p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 The p-GaInP base layer is deposited at 630°C on the P composite back surface field layer. 0.49 In 0.51 P, thickness 0.9 μm, doped with DEZn source, doping concentration 1~8×10 16 cm -3 ;

[0050] L. Deposit an n-GaInP emitter layer on the p-GaInP base layer at 630°C. The thickness of the n-GaInP emitter layer is 0.1 μm. The doping source is SiH4 and the doping concentration is 1×10 18 cm -3 ;

[0051] M. Deposit an n-AlInP window layer on the n-GaInP emitter layer at 630°C. The n-AlInP window layer is deposited to a thickness of 0.1 μm and doped with a SiH4 source at a doping concentration of 1×10 18 cm -3 ;

[0052] N. Deposit an n+-GaAs ohmic contact layer on the n-AlInP window layer at 630°C. The n+-GaAs ohmic contact layer is deposited to a thickness of 0.5 μm and doped with a SiH4 source with a doping concentration greater than 5×10 18 cm -3 .

[0053] It should be noted that although the preferred embodiments of the present invention have been shown and described, it is understood by those skilled in the art that changes may be made to these embodiments without departing from the shape and principle of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer, characterized in that: A composite back surface field layer structure is introduced into the middle cell and the top cell of the conventional space lattice-matched GaInP / GaInAs / Ge structure to improve the collection efficiency of photogenerated carriers, thereby improving the cell efficiency; The specific steps are as follows: Using AXITRON's 2600G3 MOCVD equipment, n-AlGaInP nucleation layer, n-GaAs / n-GaInAs buffer layer, n++-GaAs / p++-GaAs tunneling junction layer, p-AlGaAs / p-AlGaInAs (DBR) reflective layer, p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, p-GaInAs base layer, n-GaInAs emitter layer, n-AlInP window layer, n++-GaInP / p++-AlGaAs tunneling junction layer, p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, p-GaInP base layer, n-GaInP emitter layer, n-AlInP window layer and n+-GaAs ohmic contact layer; The substrate material is p-type Ge substrate, the substrate is doped with Ga source, and the doping concentration is 0.2E18~3E18cm -3 , thickness is 130-150μm, cutting angle is 9°; The n-AlGaInP nucleation layer is deposited with a thickness of 0.01 μm and doped with SiH4 source at a doping concentration of 1 to 2×10 18 cm -3 ; The n-GaAs / n-GaInAs buffer layer is deposited with a thickness of 0.5 μm and doped with SiH4 source with a doping concentration of ≥1×10 18 cm -3 ; n++-GaAs / p++-GaAs tunneling junction layer, where the n++-GaAs layer is deposited with a thickness of 0.01-0.03 μm, doped with SiH4 source, and the doping concentration is ≥5×10 18 cm -3 The p++-GaAs layer is deposited with a thickness of 0.01-0.03 μm and doped with a CCl4 source with a doping concentration of ≥1×10 19 cm -3 ; The p-AlGaAs / p-AlGaInAs (DBR) reflective layer is deposited with a thickness of 1.8 μm and doped with DEZn source at a doping concentration of 5×10 17 cm -3 ; p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, in which Al 0.3 Ga 0.7 The As thickness is 0.02 μm and the doping concentration is 8×10 17 ~1.2×10 18 cm -3 , Ga 0.5 In 0.5 The P thickness is 0.1 μm and the doping concentration is 5×10 17 ~8×10 17 cm -3 ; The p-GaInAs base layer is deposited to a thickness of 2.1 μm and doped with DEZn source with a doping concentration of 2 to 8×10 16 cm -3 ; The deposition thickness of the n-GaInAs emitter layer is 0.1 μm, and the doping concentration is 1×10 18 cm -3 ; The n-AlInP window layer is deposited with a thickness of 0.1 μm and doped with SiH4 source at a doping concentration of 1×10 18 cm -3 ; n++-GaInP / p++-AlGaAs tunneling junction layer, where the n++-GaInP layer is deposited with a thickness of 0.01-0.03 μm, doped with SiH4 source, and the doping concentration is ≥5×10 18 cm -3 The p++-AlGaAs layer is deposited with a thickness of 0.01-0.03 μm and doped with a CCl4 source with a doping concentration of ≥5×10 19 cm -3 ; p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, in which Al 0.33 Ga 0.15 In 0.52 The P thickness is 0.02 μm and the doping concentration is 2×10 18 cm -3 ,Al 0.1 Ga 0.4 In 0.5 The P thickness is 0.1 μm and the doping concentration is 5×10 17 ~1×10 18 cm -3 ; The p-GaInP base layer is deposited with a thickness of 0.9 μm and a composition of Ga 0.49 In 0.51 P, doped with DEZn source, doping concentration is 1~8×10 16 cm -3 ; The deposition thickness of the n-GaInP emitter layer is 0.1 μm, and the doping concentration is 1×10 18 cm -3 ; The n+-GaAs ohmic contact layer is deposited with a thickness of 0.5 μm and doped with SiH4 source with a doping concentration greater than 5×10 18 cm -3 .

2. The method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer according to claim 1, characterized in that: Composite back surface field structures are introduced into the top cell and the middle cell respectively. The composite back surface field material of the middle cell is p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P, the top cell composite back surface field material is p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P.

3. The method for manufacturing a composite back surface field space GaInP / GaInAs / Ge cell epitaxial wafer according to claim 1, characterized in that: Medium battery p-Al 0.3 Ga 0.7 As / p-Ga 0.5 In 0.5 P composite back surface field layer, in which Al 0.3 Ga 0.7 The As layer thickness is 0.02 μm and the doping concentration is 8×10 17 ~1.2×10 18 cm -3 , Ga 0.5 In 0.5 The thickness of the P layer is 0.1 μm and the doping concentration is 5×10 17 ~8×10 17 cm -3 ; Top cell p-Al 0.33 Ga 0.15 In 0.52 P / p-Al 0.1 Ga 0.4 In 0.5 P composite back surface field layer, in which Al 0.33 Ga 0.15 In 0.52 The thickness of the P layer is 0.02 μm, and the doping concentration is 1 to 2×10 18 cm -3 ,Al 0.1 Ga 0.4 In 0.5 The thickness of the P layer is 0.1 μm and the doping concentration is 5×10 17 ~1×10 18 cm -3 .

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