CN111341872B - Gallium arsenide solar cell epitaxial structure and growth method thereof - Google Patents

Abstract

The invention relates to an epitaxial structure of a gallium arsenide solar cell and a growth method thereof. The cell comprises a Ge bottom cell, a GaAs middle cell and a GaInP top cell that are stacked in sequence, wherein the GaAs middle cell and the GaInP top cell are both It includes a back layer and an emission layer; the back layer of the GaAs middle cell includes a delta-doped p-type GaInP layer, and the emission layer includes a delta-doped n-type GaAs layer; the back layer of the GaInP top cell includes a delta-doped The p-type GaInP layer, and the emission layer includes a delta-doped n-type GaInP layer. In the solar cell epitaxial structure of the present invention, the back layer and the emission layer of the middle cell and the top cell are all grown by delta doping. This delta doping structure can block the extension of crystal dislocations, inhibit the spread of crystal defects, and improve the epitaxy of the solar cell. Structure reliability and photoelectric conversion efficiency.

Description

A kind of gallium arsenide solar cell epitaxial structure and growth method thereof

technical field

The invention relates to the technical field of solar cells, in particular to an epitaxial structure of a gallium arsenide solar cell.

Background technique

Three-junction GaAs solar cells have good spectral responsiveness and high photoelectric conversion efficiency, and are usually used in aerospace and concentrating photovoltaic power stations. At present, the more common triple-junction GaAs solar cells are Ge bottom cell, GaAs middle cell and GaInP top cell structure, and their energy bands increase sequentially from bottom to top, respectively absorbing light of different wavelengths, thereby achieving full-spectrum absorption. However, the bottom cells of the current triple-junction gallium arsenide cells all use the direct doping growth method, that is, the growth source and the doping source are used for growth at the same time. This growth method will bring a certain amount of defects to the epitaxial structure, making the Its crystal quality is affected, thereby affecting the photoelectric conversion performance and its reliability.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a gallium arsenide solar cell epitaxial structure, including a Ge bottom cell, a GaAs middle cell and a GaInP top cell that are stacked in sequence, wherein the GaAs middle cell and the GaInP top cell both include a back layer and a GaInP top cell. emission layer;

The back layer of the GaAs middle cell includes a delta-doped p-type GaInP layer, and the emission layer includes a delta-doped n-type GaAs layer; the back layer of the GaInP top cell includes a delta-doped p-type GaInP layer, and the emission layer includes a delta-doped p-type GaInP layer. A delta-doped n-type GaInP layer is included.

For Ge bottom cells, GaAs mid cells and GaInP top cell composite cells, there are mid cells and top cells that can be delta-doped, and for mid cells and top cells, which generally include the back layer, base and emitter Layers and other structures, if you want to improve the performance of the battery by delta doping, there are many options, such as delta doping only in the middle battery or top battery, or you can do both batteries. For delta doping, only a part of the back layer or the emission layer can be doped, or all of them can be delta doped. It is found in the present invention that doping the back layers in both the middle cell and the top cell, and when the structures in the base layer and the emission layer are not completely delta doped layers, can significantly improve the structure of the cell and improve the efficiency of the cell.

Preferably, the back layer of the battery in the GaAs further includes a p-type GaInP layer that is attached to the delta-doped p-type GaInP layer close to the surface of the Ge bottom battery, and is grown by direct doping. It also includes an n-type GaAs layer that is attached to the surface of the delta-doped n-type GaAs layer close to the Ge bottom battery and grown by direct doping;

Preferably, the back layer of the GaInP top cell further comprises a p-type GaInP layer attached to the delta-doped p-type GaInP layer close to the surface of the Ge bottom cell and grown by direct doping, and the emission layer also It includes the n-type GaInP layer that is attached to the surface of the delta-doped n-type GaInP layer close to the Ge bottom cell and grown by direct doping.

In each base layer or emission layer, in addition to the structure of the delta doped layer, a layered structure obtained by direct doping growth is also provided. Effectively improve the efficiency of the battery.

Preferably, in the back layer of the GaAs medium cell, the thickness of the p-type GaInP layer obtained by direct doping growth is 20-40 nm, and the thickness of the p-type delta-doped GaInP layer is 20-40 nm; In the emission layer of the GaAs medium battery, the thickness of the n-type GaAs layer obtained by direct doping growth is 25-60 nm, and the thickness of the delta-doped n-type GaAs emission layer is 25-60 nm;

Preferably, in the back layer of the GaInP top cell, the thickness of the p-type GaInP layer obtained by direct doping growth is 20-40 nm, and the thickness of the delta-doped p-type GaInP is 20-40 nm; In the emission layer of the GaInP top cell, the thickness of the n-type GaInP layer obtained by direct doping growth is 25-60 nm, and the thickness of the delta-doped n-type GaInP is 25-60 nm.

Preferably, towards the direction of the Ge bottom cell, the GaAs middle cell includes a window layer, an emission layer, a base region and a back layer that are stacked in sequence; towards the direction of the GaAs middle cell, the GaInP top cell It includes a contact layer, a window layer, an emission layer, a base region and a back layer that are stacked in sequence. The window layer of the medium cell is mainly used to transmit sunlight with a wavelength above 670 nm. After the base region of the medium cell absorbs sunlight between 670-870 nm, an induced electromotive force is generated at the pn junction interface between the base region and the emission layer, and the back layer starts. To enhance the photon absorption to enhance the efficiency. The window layer of the top cell is mainly used to transmit the full spectrum of the sun. The base region absorbs wavelengths below 670 nm to generate an induced electromotive force at the interface between the base region and the emission layer, and the back layer enhances photon absorption to enhance efficiency.

Preferably, a p-type Ge substrate, an n-type Ge emission layer and an n-type GaInP window layer are stacked in sequence in the Ge bottom cell. The germanium bottom cell mainly absorbs wavelengths above 870nm.

Preferably, the Ge bottom cell and the GaAs are connected through a tunnel junction, and the GaAs and the GaInP are connected through a tunnel junction.

Further preferably, the material of the tunnel junction is GaAs. The lower internal resistance of the tunneling junction material enables better stringing of cells to achieve the best current density.

Another object of the present invention is to protect the preparation method of the solar cell of the present invention, including:

To form the delta-doped p-type GaInP layer in the back layer of the GaAs medium cell, adopt the metal organic compound chemical vapor deposition method, first grow 2-4 nm of GaInP without doping source, and then only pass 1-3 phosphine. seconds, and then feed the doping source for 2 to 4 seconds to complete one cycle of growth; 5 to 20 cycles of cyclic growth are thus performed;

To form the delta-doped n-type GaAs layer in the emission layer of the GaAs medium cell, adopt the metal organic compound chemical vapor deposition method, first grow 2-4nm GaAs without silane, and then only pass arsine for 1-3 seconds, and then The silane was passed in for 2-4 seconds to complete one cycle of growth, and 6-30 cycles of cyclic growth were thus performed.

To form the delta-doped p-type GaInP layer in the back layer of the GaInP top cell, adopt the metal organic compound chemical vapor deposition method, first grow 2-4 nm of GaInP without doping source, and then only pass 1 to 3 of phosphine. seconds, and then pass in the doping source for 2 to 4 seconds to complete one cycle of growth, and thus carry out 5 to 20 cycles of cyclic growth;

To form the delta-doped n-type GaInP layer in the emission layer of the GaInP top cell, adopt the metal organic compound chemical vapor deposition method, first grow 2-4 nm GaInP without silane, and then only pass phosphine for 1-3 seconds, and then The silane was introduced for 2 to 4 seconds to complete one cycle of growth, and 6 to 30 cycles of cyclic growth were thus performed.

Preferably, the conditions of the metal organic compound chemical vapor precipitation method are as follows: the temperature is 550-850° C., and the pressure is 50-200 Torr.

Preferably, the doping source for the back layer of the cell or top cell is one of CCl ₄ , CBr ₄ or diethylzinc (DEZn).

As a preferred solution, the preparation method of the battery of the present invention comprises the following steps:

1) Using the metal organic compound chemical vapor deposition method (MOCVD), the temperature of the reaction chamber is controlled to be 680 ° C to 850 ° C, and the pressure is 50 to 200 torr, and n-type phosphorus is diffused on the upper surface of the p-type Ge substrate to obtain n-type Ge. Emission layer, and then grow a 20 to 60 nm thick GaInP buffer layer on it as the window layer of the bottom cell;

2) growing n-type GaAs of 5-10 nm and p-type GaAs of 5 to 10 nm on the window layer as the first tunneling junction;

3) Grow a p-type GaInP back layer with a thickness of 20 to 40 nm on the first tunnel junction by direct doping growth, and then use a delta doping method to grow a delta doped 20 to 40 nm thick Back layer; delta doping is specifically, first grow GaInP of 2 to 4 nm, then pass only phosphine for 1 to 3 seconds, and then pass through the doping source for 2 to 4 seconds; 5 to 20 cycles of cyclic growth are performed in this way;

4) growing p-type GaAs with a thickness of about 2000 to 3000 nm on the delta-doped back layer as the base region of the medium cell;

5) Grow an n-type GaAs emission layer with a thickness of 25 to 60 nm by direct doping growth, and then use a delta doping method to obtain a delta-doped n-type GaAs emission layer with a thickness of 25 to 60 nm; delta doping Specifically, first grow 2 to 4 nm of GaAs without silane, then only pass arsine for 1 to 3 seconds, and then pass silane for 2 to 4 seconds, and this cycle grows for 6 to 30 cycles;

6) A 40 to 120 nm thick n-type AlGaInP window layer is grown thereon;

7) growing n-type GaAs and p-type GaAs on the window layer as a second tunneling junction;

8) A top cell p-type GaInP back layer with a thickness of 20 to 40 nm is grown on the second tunnel junction by direct doping growth, and a delta doping back layer with a thickness of 20 to 40 nm is then grown by delta doping. layer; the delta doping is specifically the GaInP with a length of 2 to 4 nm without the doping source, then only phosphine for 1 to 3 seconds, and then the doping source is turned on for 2 to 4 seconds, and so on for 5 to 20 cycles cyclic growth;

9) growing p-type GaInP with a thickness of 300 to 700 nm on the back layer as a top cell base region;

10) Grow an n-type GaInP emitting layer with a thickness of 25 to 60 nm on the base region, and then adopt a delta doping method to obtain a delta-doped n-type GaInP emitting layer with a thickness of 25 to 60 nm; the delta doping The heterogeneity is to first grow 2 to 4 nm of GaInP without silane, then only pass phosphine for 1 to 3 seconds, then turn on silane for 2 to 4 seconds, and then grow 2 to 4 nm of GaInP without silane, and so on for 6 to 30 cycles. cycle;

11) growing an n-type AlGaInP window layer of 20 to 60 nm;

12) The temperature is lowered to 600 to 700 degrees Celsius, and an n-type GaAs contact layer of 40 to 100 nm is grown.

The present invention has the following beneficial effects:

1) In the epitaxial structure of the triple-junction gallium arsenide solar cell of the present invention, the back layer and the emission layer of the middle cell and the top cell are all grown by delta doping. This delta doping structure can block the extension of crystal dislocation and inhibit the Crystal defects spread, improving reliability and photoelectric conversion efficiency.

2) The solar cell of the present invention can reduce the junction temperature when the cell works, and can obtain higher open-circuit voltage and short-circuit current.

Description of drawings

FIG. 1 is a schematic structural diagram of the battery described in Example 1.

Detailed ways

The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

Example 1

The present embodiment relates to an epitaxial structure of a gallium arsenide solar cell, which sequentially includes a Ge bottom cell, a GaAs middle cell and a GaInP top cell arranged in layers;

Its specific structure is, from bottom to top, including p-Ge substrate, n-Ge emission layer obtained by n-type phosphorus diffusion on germanium substrate, n-GaInP window layer with thickness of 30nm, n-GaInP with thickness of 5nm. GaAs tunneling junction, p-GaAs tunneling junction with a thickness of 5nm, p-GaInP back layer 1 with a thickness of 30nm, delta-doped p-GaInP back layer 2 with a thickness of 32nm, p-GaAs base with a thickness of 2500nm region, n-GaAs emitter layer 1 with a thickness of 30 nm, delta-doped n-GaAs emitter layer 2 with a thickness of 32 nm, n-AlGaInP window layer with a thickness of 80 nm, n-GaAs tunneling junction with a thickness of 5 nm, thickness 5nm p-GaAs tunnel junction, 30nm thickness p-GaInP back layer 1, 32nm thickness delta doped p-GaInP back layer 2, 500nm thickness p-GaInP base region, 30nm thickness n-GaInP emission layer 1, delta-doped n-GaInP emission layer 2 with a thickness of 32 nm, n-AlGaInP window layer with a thickness of 40 nm, and n-GaAs contact layer with a thickness of 50 nm. Its structure diagram is shown in Figure 1.

This embodiment relates to the preparation method of the battery of the present invention, which includes the following steps:

1) Use MOCVD equipment for epitaxial layer growth, set the temperature of the reaction chamber to 750°C and the pressure to 150torr, and perform n-type phosphorus diffusion on the upper surface of the p-type Ge substrate as the emission layer of the bottom cell, and then grow on it The 30nm n-type GaInP buffer layer is used as the window layer of the bottom cell, and silane is used for the n-type doping here.

In the following steps, silane is used for the n-type doping of the epitaxial layer, and CBr ₄ is used for the p-type doping;

2) growing n-type GaAs with a thickness of 5 nm, and p-type GaAs with a thickness of 5 nm as the first tunneling junction;

3) Grow a p-type GaInP back layer 1 with a thickness of 30 nm, and then use a delta doping method to grow a p-type GaInP back layer 2, specifically, grow 2 nm of GaInP (without CBr ₄ ), and then only pass phosphine for 2 seconds, Turn on CBr ₄ again for 3 seconds, and perform 16 cycles of growth in this way to obtain a back layer 2 with a thickness of 32 nm;

4) Grow p-type GaAs with a thickness of 2500 nm as the base region of the medium cell, and still use CBr ₄ for p-type doping;

5) Grow an n-type GaAs emission layer 1 with a thickness of 30 nm, and then grow a delta-doped n-type GaAs emission layer 2 with a thickness of 32 nm by delta doping. The specific operation is to grow 2 nm of GaAs without silane, Then only pass arsine for 2 seconds, then turn on silane for 3 seconds, and this cycle grows for 16 cycles to obtain a delta-doped n-type GaAs emission layer 2 with a thickness of 32 nm;

6) Grow an n-type AlGaInP window layer with a thickness of 80 nm;

7) growing 5nm n-type GaAs and 5nm p-type GaAs as the second tunneling junction;

8) Grow a top cell p-type GaInP back layer 1 with a thickness of 30 nm, and then use a delta doping method to grow a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm. The specific operation of the delta doping growth is, first grow 2nm of GaInP without CBr ₄ doping source, and then only phosphine for 2 seconds, then turn on the doping source for 3 seconds, and so on for 16 cycles to obtain a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm;

9) Grow p-type GaInP with a thickness of 500 nm as the base region of the top cell;

10) Grow an n-type GaInP emission layer 1 with a thickness of 30 nm, and then grow a delta-doped n-type GaInP emission layer 2 with a thickness of 32 nm by delta doping. The specific operation of the delta doping growth is, first grow 2nm GaInP without silane, then only phosphine for 2 seconds, and then silane is turned on for 2 seconds, so that the cycle grows, the period is 16, and the delta-doped n-type GaInP emission layer 2 with a thickness of 32nm is obtained;

11) Grow a 40nm n-type AlGaInP window layer;

12) Lower the temperature to 670 degrees to grow a 50nm n-type GaAs contact layer.

Example 2

This embodiment relates to an epitaxial structure of a gallium arsenide solar cell. Compared with Embodiment 1, the difference between this embodiment is that the thickness of the delta-doped n-GaInP emission layer 2 is 40 nm.

The epitaxial structure of the gallium arsenide solar cell described in this embodiment sequentially includes a stacked Ge bottom cell, a GaAs middle cell, and a GaInP top cell;

Its specific structure is, from bottom to top, including p-Ge substrate, n-Ge emission layer obtained by n-type phosphorus diffusion on germanium substrate, n-GaInP window layer with thickness of 30nm, n-GaInP with thickness of 5nm. GaAs tunneling junction, p-GaAs tunneling junction with a thickness of 5nm, p-GaInP back layer 1 with a thickness of 30nm, delta-doped p-GaInP back layer 2 with a thickness of 32nm, p-GaAs base with a thickness of 2500nm region, n-GaAs emitter layer 1 with a thickness of 30 nm, delta-doped n-GaAs emitter layer 2 with a thickness of 32 nm, n-AlGaInP window layer with a thickness of 80 nm, n-GaAs tunneling junction with a thickness of 5 nm, thickness 5nm p-GaAs tunnel junction, 30nm thickness p-GaInP back layer 1, 32nm thickness delta doped p-GaInP back layer 2, 500nm thickness p-GaInP base region, 30nm thickness An n-GaInP emission layer 1, a delta-doped n-GaInP emission layer 2 with a thickness of 40 nm, an n-AlGaInP window layer with a thickness of 40 nm, and an n-GaAs contact layer with a thickness of 50 nm.

This embodiment relates to the preparation method of the battery of the present invention, which includes the following steps:

1) Using MOCVD equipment to grow the epitaxial layer, set the temperature of the reaction chamber to 750°C and the pressure to 150torr, and perform n-type phosphorus diffusion on the upper surface of the p-type Ge substrate as the emission layer of the bottom cell. Then grow a 30nm n-type GaInP buffer layer on it as the window layer of the bottom cell, where SiH4 is used for n-type doping, silane is used for n-type doping in subsequent epitaxial layers, and CBr4 is used for p-type doping;

2) growing n-type GaAs with a thickness of 5 nm, and p-type GaAs with a thickness of 5 nm as the first tunneling junction;

3) Grow a p-type GaInP back layer 1 with a thickness of 30nm, and then use a delta doping method to grow a 2nm GaInP without CBr4 (doping source), and then only pass phosphine for 2 seconds, then turn on CBr for 43 seconds, and so on. 16 cycles of growth to grow a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm;

4) The p-type GaAs with a thickness of 2500 nm is grown as the base region of the medium battery, and CBr4 is still used for the p-type doping;

5) Grow an n-type GaAs emission layer 1 with a thickness of 30 nm, and then use delta doping to grow 2 nm of GaAs without silane, then only pass arsine for 2 seconds, turn on silane for 3 seconds, and grow 2 nm without passing through The GaAs of silane is grown cyclically in this way, and its period is 16, and a delta-doped n-type GaAs emission layer 2 with a thickness of 32 nm is obtained;

6) Grow an n-type AlGaInP window layer with a thickness of 80 nm;

7) growing 5nm n-type GaAs and 5nm p-type GaAs as the second tunneling junction;

8) Grow the top cell p-type GaInP back layer 1 with a thickness of 30 nm, and then use the delta doping method to first grow 2 nm of GaInP without CBr4 doping source, and then only pass phosphine for 2 seconds, and then turn on the doping source 3 Second, 16 cycles are performed in this way to obtain a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm;

9) Grow p-type GaInP with a thickness of 500 nm as the base region of the top cell;

10) Grow an n-type GaInP emission layer 1 with a thickness of 30 nm, and then use delta doping to grow 2 nm of GaInP without silane, and then only pass phosphine for 2 seconds, and then turn on silane for 2 seconds. is 20 to obtain a delta-doped n-type GaInP emission layer 2 with a thickness of 40 nm;

11) Grow a 40nm n-type AlGaInP window layer;

12) Lower the temperature to 670 degrees to grow a 50nm n-type GaAs contact layer.

Example 3

This embodiment relates to an epitaxial structure of a gallium arsenide solar cell. Compared with Embodiment 1, the difference lies in that the thickness of the p-type delta-doped GaInP back layer 2 is 40 nm.

The epitaxial structure described in this embodiment sequentially includes a stacked Ge bottom cell, a GaAs middle cell and a GaInP top cell;

Its specific structure is, from bottom to top, including p-Ge substrate, n-Ge emission layer obtained by n-type phosphorus diffusion on germanium substrate, n-GaInP window layer with thickness of 30nm, n-GaInP with thickness of 5nm. GaAs tunneling junction, p-GaAs tunneling junction with a thickness of 5 nm, p-GaInP back layer 1 with a thickness of 30 nm, delta-doped p-GaInP back layer 2 with a thickness of 40 nm, p-GaAs base with a thickness of 2500 nm region, n-GaAs emitter layer 1 with a thickness of 30 nm, delta-doped n-GaAs emitter layer 2 with a thickness of 32 nm, n-AlGaInP window layer with a thickness of 80 nm, n-GaAs tunneling junction with a thickness of 5 nm, thickness 5nm p-GaAs tunnel junction, 30nm thickness p-GaInP back layer 1, 32nm thickness delta doped p-GaInP back layer 2, 500nm thickness p-GaInP base region, 30nm thickness n-GaInP emission layer 1, delta-doped n-GaInP emission layer 2 with a thickness of 32 nm, n-AlGaInP window layer with a thickness of 40 nm, and n-GaAs contact layer with a thickness of 50 nm.

This embodiment relates to the preparation method of the battery of the present invention, which includes the following steps:

1) Using MOCVD equipment to grow the epitaxial layer, set the temperature of the reaction chamber to 750°C and the pressure to 150torr, and perform n-type phosphorus diffusion on the upper surface of the p-type Ge substrate as the emission layer of the bottom cell. Then grow a 30nm n-type GaInP buffer layer on it as the window layer of the bottom cell, where SiH4 is used for n-type doping, silane is used for n-type doping in subsequent epitaxial layers, and CBr4 is used for p-type doping;

2) growing n-type GaAs with a thickness of 5 nm, and p-type GaAs with a thickness of 5 nm as the first tunneling junction;

3) Grow the p-type GaInP back layer 1 with a thickness of 30nm, and then use the delta doping method to grow 2nm GaInP without CBr4 (doping source), and then only pass phosphine for 2 seconds, then turn on CBr for 43 seconds, and grow again 2nm of GaInP without CBr4 was grown in this way for 20 cycles to grow a delta-doped p-type GaInP back layer 2 with a thickness of 40nm;

4) The p-type GaAs with a thickness of 2500 nm is grown as the base region of the medium battery, and CBr4 is still used for the p-type doping;

5) Grow an n-type GaAs emission layer 1 with a thickness of 30 nm, and then use delta doping to grow 2 nm of GaAs without silane, then only pass arsine for 2 seconds, turn on silane for 3 seconds, and grow 2 nm without passing through The GaAs of silane is grown cyclically in this way, and its period is 16, and a delta-doped n-type GaAs emission layer 2 with a thickness of 32 nm is obtained;

6) Grow an n-type AlGaInP window layer with a thickness of 80 nm;

7) growing 5nm n-type GaAs and 5nm p-type GaAs as the second tunneling junction;

8) Grow the top cell p-type GaInP back layer 1 with a thickness of 30 nm, and then use the delta doping method to first grow 2 nm of GaInP without CBr4 doping source, and then only pass phosphine for 2 seconds, and then turn on the doping source 3 Second, re-grow 2 nm of GaInP without doping source, and perform 16 cycles in this way to obtain a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm;

9) Grow p-type GaInP with a thickness of 500 nm as the base region of the top cell;

10) Grow an n-type GaInP emission layer 1 with a thickness of 30 nm, and then use delta doping to grow 2 nm of GaInP without silane, then only pass phosphine for 2 seconds, turn on silane for 2 seconds, and grow 2 nm without silane The GaInP is grown in such a cycle, and its period is 16 to obtain a delta-doped n-type GaInP emission layer 2 with a thickness of 32 nm;

11) Grow a 40nm n-type AlGaInP window layer;

12) Lower the temperature to 670 degrees to grow a 50nm n-type GaAs contact layer.

Comparative Example 1

Compared with Example 1, the difference of this comparative example is that the p-GaInP back layer 1 and the n-GaAs emission layer 1 are not provided in the GaAs mid-cell.

Comparative Example 2

Compared with Example 1, the difference of this comparative example is that the GaInP top cell is not provided with the p-GaInP back layer 1 and the n-GaInP emission layer 1

Comparative Example 3

Compared with Example 1, the difference of this comparative example is that the preparation method of the delta-doped back layer of the battery in the GaAs is to first grow 1 nm of GaInP without CBr ₄ (doping source), and then only pass phosphorus. Alkane for 2 seconds, then turn on CBr ₄ for 3 seconds, and thus carry out 32 cycles of growth to grow a delta-doped p-type GaInP back layer 2 with a thickness of 32 nm; the preparation method of the delta-doped emission layer is to grow 1 nm first without passing through For GaAs of silane, only pass arsine for 2 seconds, then turn on silane for 3 seconds, and so on, the cycle is 32, and a delta-doped n-type GaAs emission layer 2 with a thickness of 32 nm is obtained.

Comparative Example 4

Compared with Example 1, the difference of this comparative example is that the delta-doped back layer growth method of the GaAs top cell is to first grow 6 nm of GaInP without CBr4 doping source, and then only pass phosphine for 4 seconds. Then turn on the doping source for 6 seconds, and perform 5 cycles in this way to obtain a delta-doped p-type GaInP back layer 2 with a thickness of 30 nm; the preparation method of the delta-doped emission layer is to grow 6 nm of GaInP without silane, and then The phosphine was only passed through for 4 seconds, and the silane was turned on for 6 seconds. The regeneration cycle was performed in 5 cycles, and a delta-doped n-type GaInP emitting layer with a thickness of 30 nm was obtained.

Comparative Example 5

This comparative example involves common composite cells on the market, including stacked Ge bottom cells, GaAs middle cells, and GaInP top cells. The specific structures are:

The specific structure of a common battery is, from bottom to top, including a p-Ge substrate, an n-Ge emitter layer with n-type phosphorus diffusion on a germanium substrate, and an n-GaInP window layer with a thickness of 30nm and a thickness of 5nm. n-GaAs tunnel junction, p-GaAs tunnel junction with thickness of 5nm, p-GaInP back layer with thickness of 60nm 1, p-GaAs base with thickness of 2500nm, n-GaAs emitter layer with thickness of 70nm 1 , an n-AlGaInP window layer with a thickness of 80 nm, an n-GaAs tunnel junction with a thickness of 5 nm, a p-GaAs tunnel junction with a thickness of 5 nm, a p-GaInP back layer with a thickness of 60 nm, and a p-GaInP with a thickness of 500 nm. GaInP base region, n-GaInP emission layer 1 with thickness of 60nm, n-AlGaInP window layer with thickness of 40nm, n-GaAs contact layer with thickness of 50nm.

Experimental example

The photoelectric conversion efficiency of the solar epitaxial structure of embodiment and comparative example is measured, and its measuring method is under AM1.5D, 500 times of concentrating test conditions, and its photoelectric conversion efficiency is respectively:

It can be seen from the above data that only the doping growth of the middle cell and the top cell is far less effective than the effect of doping growth in both the middle cell and the top cell, and the delta described in this application is used. The effect of doping growth is more ideal.

In the process of research, the present invention also tried to perform only delta doping on the back layer and the emissive layer, that is, the back layer and the emissive layer only contain one delta doped layer and no ordinary doped layer. It was found that Compared with the common doping method, the effect is not significantly improved. An attempt was also made to perform delta doping only on the back layer of the middle cell and the top cell, without performing delta doping on the emissive layer, and the effect was not as ideal as the method of the present invention.

Although the present invention has been described in detail above with general description, specific embodiments and tests, some modifications or improvements can be made on the basis of the present invention, which is obvious to those skilled in the art . Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (10)

1. The preparation method of the gallium arsenide solar cell epitaxial structure is characterized in that the cell comprises a Ge bottom cell, a GaAs middle cell and a GaInP top cell which are sequentially stacked, wherein the GaAs middle cell and the GaInP top cell respectively comprise a back layer and an emitting layer;

the back layer of the GaAs middle cell comprises a delta-doped p-type GaInP layer, and the emitting layer comprises a delta-doped n-type GaAs layer; the back layer of the GaInP top cell comprises a delta doped p-type GaInP layer and the emitter layer comprises a delta doped n-type GaInP layer;

forming a delta-doped p-type GaInP layer in the back layer of the GaAs medium cell, growing GaInP which is not connected with a doping source and has the length of 2-4 nm by adopting a metal organic compound chemical vapor deposition method, only connecting phosphine for 1-3 seconds, and opening the doping source for 2-4 seconds to finish the growth of one period; thus carrying out 5-20 cycles of cyclic growth;

and/or forming a delta-doped n-type GaAs layer in an emission layer of the GaAs mesobattery, growing GaAs which is not passed through silane for 2-4 nm by adopting a metal organic compound chemical vapor deposition method, then passing through arsine for 1-3 seconds, then opening silane for 2-4 seconds, completing the growth of one period, and thus performing the cyclic growth for 6-30 periods.

2. The method for preparing the epitaxial structure of the GaAs solar cell of claim 1, wherein the back layer of the GaAs intermediate cell further comprises a p-type GaInP layer grown by direct doping attached to the surface of the delta-doped p-type GaInP layer close to the Ge base cell, and the emission layer further comprises an n-type GaAs layer grown by direct doping attached to the surface of the delta-doped n-type GaAs layer close to the Ge base cell;

and/or the back layer of the GaInP top cell further comprises a p-type GaInP layer which is attached to the surface of the delta-doped p-type GaInP layer close to the Ge bottom cell and is grown through direct doping, and the emission layer further comprises an n-type GaInP layer which is attached to the surface of the delta-doped n-type GaInP layer close to the Ge bottom cell and is grown through direct doping.

3. The method for preparing the epitaxial structure of the GaAs solar cell according to claim 2, wherein in the back layer of the GaAs mesocell, the thickness of the p-type GaInP layer grown by direct doping is 20 to 40nm, and the thickness of the p-type delta-doped GaInP layer is 20 to 40nm; in the emitting layer of the GaAs middle battery, the thickness of the n-type GaAs layer obtained by direct doping growth is 25-60 nm, and the thickness of the delta-doped n-type GaAs emitting layer is 25-60 nm;

and/or, in the back layer of the GaInP top cell, the thickness of the p-type GaInP layer obtained by direct doping growth is 20-40nm, and the thickness of the delta-doped p-type GaInP is 20-40 nm; in the emitting layer of the GaInP top cell, the thickness of the n-type GaInP layer obtained by direct doping growth is 25-60nm, and the thickness of the delta-doped n-type GaInP is 25-60 nm.

4. The method for preparing the epitaxial structure of the GaAs solar cell according to any one of claims 1 to 3, characterized in that, towards the Ge bottom cell, the GaAs middle cell comprises a window layer, an emitting layer, a base region and a back layer which are sequentially stacked; and the GaInP top cell comprises a contact layer, a window layer, an emitting layer, a base region and a back layer which are sequentially stacked towards the GaAs middle cell.

5. The method for preparing the epitaxial structure of the gallium arsenide solar cell as claimed in claim 1, wherein the Ge bottom cell is connected to the GaAs middle cell through a tunnel junction, and the GaAs and the GaInP top cell are connected through a tunnel junction; the tunneling junction is GaAs.

6. The method for preparing the epitaxial structure of the gallium arsenide solar cell as claimed in claim 1, wherein towards the GaAs cell, a p-type Ge substrate, an n-type Ge emitting layer and an n-type GaInP window layer are sequentially stacked in the Ge-based cell.

7. The method for preparing the epitaxial structure of the gallium arsenide solar cell according to claim 1, comprising:

forming a delta-doped p-type GaInP layer in the back layer of the GaInP top cell, growing GaInP which is not connected with a doping source and has a length of 2-4 nm by adopting a metal organic compound chemical vapor deposition method, only introducing phosphane for 1-3 seconds, opening the doping source for 2-4 seconds, completing the growth of one period, and thus carrying out the cyclic growth of 5-20 periods;

and forming a delta-doped n-type GaInP layer in the emitting layer of the GaInP top battery, growing 2-4 nm of GaInP which is not passed through silane by adopting a metal organic compound chemical vapor deposition method, then passing through phosphine for 1-3 seconds, then opening silane for 2-4 seconds to complete the growth of one period, and thus carrying out 6-30 periods of cyclic growth.

8. The method for preparing the epitaxial structure of the gallium arsenide solar cell as claimed in claim 1 or 7, wherein the condition of the metal organic compound chemical vapor deposition method is 550-850 ℃ and 50-200 torr pressure.

9. The method for preparing the epitaxial structure of the gallium arsenide solar cell as claimed in claim 8, wherein the middle cell or the top cell back layer doping source is CCl ₄ 、CBr ₄ Or diethyl zinc.

10. A gallium arsenide solar cell epitaxial structure, wherein said gallium arsenide solar cell epitaxial structure is prepared by the preparation method of any of claims 1-9.

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