GaAs thin film grown on Si substrate, and preparation method for GaAs thin film grown on Si substrate

Abstract

Disclosed is a preparation method for a GaAs thin film grown on an Si substrate, said method comprising the following steps: (1) Si (111) substrate cleaning; (2) Si (111) substrate preprocessing; (3) Si (111) substrate oxide film removal; (4) first In.sub.xGa.sub.1-xAs buffer layer growth; (5) first In.sub.xGa.sub.1-xAs buffer layer in situ annealing; (6) GaAs buffer layer growth; (7) GaAs buffer layer in situ annealing; (8) second In.sub.xGa.sub.1-xAs buffer layer growth; (9) second In.sub.xGa.sub.1-xAs buffer layer in situ annealing; (10) GaAs epitaxial thin film growth. Also disclosed is a GaAs thin film grown on an Si substrate. The GaAs thin film obtained by the present invention has a good crystal quality, an even surface, and a positive promotional significance with regard to the preparation of semiconductor devices, particularly in the field of solar cells.

Claims

1. A preparation method for a GaAs thin film grown on a Si substrate, characterized in that the method comprises the following steps: (1) cleaning a Si substrate; (2) preprocessing the Si substrate; (3) removing the oxide film from the Si substrate; (4) growing a first In.sub.xGa.sub.1-xAs buffer layer: decreasing the temperature of the substrate to 350500 C., and growing an In.sub.xGa.sub.1-xAs buffer layer with a thickness of 220 nm under the conditions of a reaction chamber pressure of 3.010.sup.52.510.sup.8 Pa, a V/III value of 2030, and a growth rate of 0.10.5 ML/s, wherein 0.05<x<0.10; (5) in situ annealing the first In.sub.xGa.sub.1-xAs buffer layer: increasing the substrate temperature to 500540 C. and annealing for 1020 min, and the pressure of the reaction chamber being 3.010.sup.52.510.sup.8 Pa; (6) growing a GaAs the buffer layer: decreasing the temperature of the substrate temperature to 350500 C., and growing a GaAs buffer layer with a thickness of 220 nm under the conditions of a reaction chamber pressure of 3.010.sup.52.510.sup.8 Pa, a V/III value of 2030, and a growth rate of 0.10.5 ML/s; (7) in situ annealing the GaAs buffer layer: increasing the substrate temperature to 500540 C. and annealing for 1020 min, the pressure of the reaction chamber being 3.010.sup.52.510.sup.8 Pa; (8) growing a second In.sub.xGa.sub.1-xAs buffer layer: decreasing the temperature of the substrate to 350500 C. and growing a second In.sub.xGa.sub.1-xAs buffer layer with a thickness of 220 nm under the conditions of a reaction chamber pressure of 3.010.sup.52.510.sup.8 Pa, a V/III value of 2030, and a growth rate of 0.10.5 ML/s, wherein 0.01<x<0.05; (9) in situ annealing the second In.sub.xGa.sub.1-xAs buffer layer: increasing the temperature of the substrate to 500540 C. for 1020 min, the pressure of the reaction chamber being 3.010.sup.52.510.sup.8 Pa; (10) growing a GaAs epitaxial film: increasing the substrate temperature to 500580 C. and growing a GaAs epitaxial film with a thickness of 100 nm1000 nm under the conditions of a reaction chamber vacuum degree of 4.010.sup.52.710.sup.8 Pa, a V/III value of 4060, and a growth rate of 0.61 ML/s.

2. The preparation method for a GaAs thin film grown on a Si substrate according to claim 1, wherein said cleaning Si substrate in step (1) refers to: washing the substrate with acetone and deionized water to remove organic compounds on the substrate surface; placing the Si substrate in a solution in a ratio of HF:H.sub.2O=1:10 for a ultrasound treatment for 110 minute; then washing the substrate with deionized water to remove surface oxide and organic compounds; and drying the cleaned substrate with high purity nitrogen.

3. The preparation method for a GaAs thin film grown on a Si substrate according to claim 1, wherein said preprocessing Si substrate in step (2) refers to: after cleaning the Si substrate, transferring the substrate into an injection chamber and pre-degassing it for 1530 minutes; then transferring it to a transfer room and degassing for 0.52 hours at a temperature of 300400 C.; and transferring the substrate into a growth chamber after the completion of degassing.

4. The preparation method for a GaAs thin film grown on a Si substrate according to claim 1, wherein said removing oxide film of the Si substrate refers to: after the Si substrate entering the growth chamber, increasing the temperature of the substrate to 9501050 C. and baking the substrate at a high temperature for 4560 minutes to remove the oxide film from the substrate surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of the structure of the GaAs thin film grown on Si substrate in an example of the present invention.

(2) FIG. 2 is a scanning electron microscope (SEM) observation of surface morphology of the GaAs thin film grown on Si substrate in an example of the present invention.

(3) FIG. 3 is a transmission electron microscope (TEM) observation of surface morphology of the GaAs thin film grown on Si substrate in an example of the present invention.

DESCRIPTION OF EXAMPLE EXAMPLES OF THE INVENTION

(4) The present invention will be further described in detail below with reference to examples and figures; however, the examples of the present invention are not limited thereto.

Example 1

(5) A preparation method for a GaAs thin film grown on a Si substrate in this example comprising the following steps:

(6) (1) Cleaning a Si (111) substrate, specifically:

(7) washing the substrate with the acetone and deionized water to remove organic compounds on the substrate surface; placing the Si substrate in a solution in a ratio of HF:H.sub.2O=1:10 for a ultrasound treatment for 1 minute; then washing the substrate with deionized water to remove surface oxides and organic compounds; and drying the cleaned substrate with high purity nitrogen.

(8) (2) Preprocessing the Si (111) substrate, specifically:

(9) after cleaning the Si (111) substrate, transferring the substrate into an injection chamber and pre-degassing it for 15 minutes; then transferring it into a transfer room and degassing for 0.5 hours at a temperature of 300 C.; and transferring the substrate into a growth chamber after the completion of degassing.

(10) 3) Removing the oxide film from the Si (111) substrate, specifically:

(11) after the Si (111) substrate enters the growth chamber, increasing the temperature of the substrate to 950 C. and baking the substrate at a high temperature for 45 minutes to remove the oxide film from the substrate surface.

(12) (4) Growing a first In.sub.xGa.sub.1-xAs buffer layer:

(13) decreasing the temperature of the substrate to 350 C., and growing an In.sub.xGa.sub.1-xAs buffer layer with a thickness of 2 nm under the conditions of a reaction chamber pressure of 3.010.sup.5 Pa, a V/III value of 20, and a growth rate of 0.1 ML/s, wherein x=0.05.

(14) (5) In situ annealing the first In.sub.xGa.sub.1-xAs buffer layer:

(15) increasing the temperature of the substrate to 500 C. for 10 min and the pressure of the reaction chamber being 3.010.sup.5 Pa.

(16) (6) Growing a GaAs buffer layer:

(17) decreasing the temperature of the substrate to 350 C., and growing a GaAs buffer layer with a thickness of 2 nm under the conditions of a reaction chamber pressure of 3.010.sup.5 Pa, a V/III value of 20, and a growth rate of 0.1 ML/s.

(18) (7) In situ annealing the GaAs buffer layer;

(19) increasing the substrate temperature to 500 C. for 10 min and the pressure of the reaction chamber being 3.010.sup.5 Pa.

(20) (8) Growing a second In.sub.xGa.sub.1-xAs buffer layer:

(21) decreasing the substrate temperature to 350 C. and growing an In.sub.xGa.sub.1-xAs buffer layer with a thickness of 2 nm under the conditions of a reaction chamber pressure of 3.010.sup.5 Pa, a V/III value of 20 and a growth rate of 0.1 ML/s; wherein x=0.01.

(22) (9) In situ annealing the second In.sub.1Ga.sub.1-xAs buffer layer:

(23) increasing the temperature of substrate to 500 C. and annealing for 10 min, the pressure of the reaction chamber being 3.010.sup.5 Pa.

(24) (10) Growing the GaAs epitaxial film:

(25) increasing the temperature of the substrate to 500 C., and growing a GaAs epitaxial film with a thickness of 100 nm under the conditions of a reaction chamber vacuum degree of 4.010.sup.5 Pa, a V/III value of 40, and a growth rate of 0.6 ML/s.

(26) As shown in FIG. 1, a GaAs thin film grown on a Si substrate comprises a substrate of a multilayer stacked structure from bottom to top, a first In.sub.xGa.sub.1-xAs buffer layer (0.05<x<0.10) 12, a GaAs buffer layer 13, a second In.sub.xGa.sub.1-xAs buffer layer (0.01<x<0.05) 14, and a GaAs epitaxial film 15.

(27) FIG. 2 is a scanning electron microscope (SEM) observation of the surface morphology of the GaAs epitaxial film prepared by the present example, as can be seen there are no pyramid-shaped protrusions on the surface and the surface is very smooth. The GaAs epitaxial film grown by the present method has a higher crystal mass compared to the GaAs obtained by the conventional method, and the width of the half-peak of the X-ray rocking curve is 200 acrsec. Owing to the addition of buffer layer, it is almost impossible to observe pyramid-shaped protrusions caused by the twin crystals on the GaAs surface, and the surface is very smooth with a mean square surface roughness of 1.8 nm.

(28) FIG. 3 is a transmission electron microscope (TEM) observation of surface morphology of the GaAs epitaxial film prepared by the present example. No threading dislocations are observed in the figure which indicates the dislocation density is greatly reduced and the crystal quality is improved.

(29) The first In.sub.xGa.sub.1-xAs (0.05<x<0.10) buffer layer, the GaAs buffer layer, the second In.sub.xGa.sub.1-xAs (0.05<x<0.10) buffer layer and the GaAs epitaxial layer of the GaAs thin film material structure in the present invention all can be prepared by molecular beam epitaxy growth or metal organic vapor deposition technique. The thicknesses of the first and second In.sub.xGa.sub.1-xAs buffer layer are controlled between 220 nm, the growth temperature is controlled between 300450 C. and the V/III value is between 2030, which reduces stresses due to the lattice mismatch by lowering the In.sub.xGa.sub.1-xAs buffer layers, to obtain GaAs thin films having a high crystal quality and smooth surface morphology.

Example 2

(30) A preparation method for a GaAs thin film grown on a Si substrate in this example comprising the following steps:

(31) (1) Cleaning a Si (111) substrate, specifically:

(32) washing the substrate with acetone and the deionized water to remove the organic compounds on the substrate surface; placing the Si substrate in a solution in a ratio of HF:H.sub.2O=1:10 for a ultrasound treatment for 10 minute; then washing the substrate with the deionized water to remove surface oxides and organic compounds; and drying the cleaned substrate with high purity nitrogen.

(33) (2) Preprocessing the Si (111) substrate, specifically:

(34) after cleaning the Si (111) substrate, transferring the substrate into an injection chamber and pre-degassing it for 30 minutes; then transferring it into a transfer room and degassing for 2 hours at a temperature of 400 C.; and transferring the substrate into a growth chamber after the completion of degassing.

(35) 3) Removing the oxide film of Si (111) substrate, specifically:

(36) after the Si (111) substrate entering the growth chamber, increasing the temperature of the substrate to 1050 C. and baking the substrate at a high temperature for 60 minutes to remove the oxide film from the substrate surface.

(37) (4) Growing a first In.sub.xGa.sub.1-xAs buffer layer:

(38) decreasing the substrate temperature to 500 C., and growing an In.sub.xGa.sub.1-xAs buffer layer with a thickness of 20 nm under the conditions of a reaction chamber pressure of 2.510.sup.8 Pa, a V/III value of 30, and a growth rate of 0.5 ML/s, wherein x=0.10.

(39) (5) In situ annealing the first In.sub.xGa.sub.1-xAs buffer layer:

(40) increasing the substrate temperature to 500540 C. for 20 min and the pressure of the reaction chamber being 2.510.sup.8 Pa.

(41) (6) Growing a GaAs buffer layer:

(42) decreasing the temperature of the substrate to 500 C., and growing a GaAs buffer layer with a thickness of 20 nm under the conditions of a reaction chamber pressure of 2.510.sup.8 Pa, a V/III value of 30, and a growth rate of 0.5 ML/s.

(43) (7) In situ annealing the GaAs buffer layer;

(44) increasing the substrate temperature to 540 C. for 20 min and the pressure of the reaction chamber being 2.510.sup.8 Pa.

(45) (8) Growing a second In.sub.xGa.sub.1-xAs buffer layer:

(46) decreasing the substrate temperature to 350500 C. and growing an In.sub.xGa.sub.1-xAs buffer layer with a thickness of 20 nm under the conditions of a reaction chamber pressure of 2.510.sup.8 Pa, a V/III value of 30 and a growth rate of 0.5 ML/s; wherein x=0.05.

(47) (9) In situ annealing the second In.sub.xGa.sub.1-xAs buffer layer:

(48) increasing the substrate temperature to 540 C. and annealing for 20 min, the pressure of reaction chamber 2.510.sup.8 Pa.

(49) (10) Growing the GaAs epitaxial film:

(50) increasing the temperature of the substrate to 580 C., and growing a GaAs epitaxial film with a thickness of 1000 nm under the conditions of a reaction chamber vacuum degree of 2.510.sup.8 Pa, a V/III value of 60, and a growth rate of 1 ML/s.

(51) The GaAs thin film grown on the Si substrate obtained in this example is similar to that of Example 1 and will not be described here.

(52) The above examples are preferred examples of the present invention; however, the examples of the present invention are not limited to the above examples, and any other alteration, modification, substitution, combination and simplification made without departing from the spiritual essence and principle of the present invention are equivalent replacements and fall within the scope of protection of the present invention.