Method and apparatus for controlling composition profile of copper indium gallium chalcogenide layers
View Patent ↗The present invention relates to method and apparatus for preparing thin films of semiconductor films for radiation detector and photovoltaic applications. In one aspect, the present invention is directed to a method of forming a Cu(In,Ga)(S,Se) 2 layer with substantially uniform Ga distribution. In a particular aspect, the method includes depositing a precursor film on the base, the precursor film including Cu, In and Ga, sulfurizing the precursor film thus forming a sulfurized precursor layer with a substantially uniform Ga distribution, and selenizing the sulfurized precursor layer to reduce the sulfur concentration therein and obtain the Cu(In,Ga)(S,Se) 2 layer with substantially uniform Ga distribution. In a further aspect, the method also includes the step of selenizing the precursor film.
1. A method of forming on a base, a Cu(In,Ga)(S,Se) 2 layer with substantially uniform Ga distribution, the method comprising;
depositing a precursor film on the base, the precursor film including Cu, In and Ga,
sulfurizing the precursor film with S thus forming a sulfurized precursor layer with a substantially uniform Ga distribution, wherein the sulfurizing causes reactions between the S and the Ga, thus creating various Ga—S phases that are distributed throughout the precursor film, and
selenizing the sulfurized precursor layer with Se to reduce the sulfur concentration therein by replacing some of the S in the Ga—S phases with Se while maintaining the Ga as distributed throughout the precursor layer from the step of sulfurizing and thereby obtaining the Cu(In,Ga)(S,Se) 2 layer with substantially uniform Ga distribution therein.
2. The method according to claim 1 wherein the step of selenizing replaces most of the S in the sulfurized layer with Se so that the resulting S/(S+Se) molar ratio is less than 0.3.
3. The method according to claim 2 wherein the resulting S/(S+Se) molar ratio is less than 0.1.
4. The method according to claim 2 wherein the step of sulfurizing includes heating the precursor film to a temperature range of 200-600° C. in the presence of S.
5. The method according to claim 4 wherein the heating takes place for a period that ranges from one minute to one hour.
6. The method according to claim 5 wherein the step of sulfurizing results in a complete reaction with S that substantially forms ternary or quarternary compound phases of Cu—In—Ga—S.
7. The method according to claim 5 wherein the step of sulfurizing results in an incomplete reaction with S that forms binary, ternary or quarternary compound phases of S with Cu, In and Ga.
8. The method according to claim 4 wherein the step of selenizing includes heating the sulfurized precursor layer to a temperature range of 400-575° C. in the presence of Se.
9. The method according to claim 8 wherein the heating of the sulfurized precursor layer takes place for a period that ranges from one minute to one hour.
10. The method according to claim 9 wherein the resulting S/(S+Se) molar ratio is less than 0.1.
11. The method according to claim 1 further including a step of reacting after the step of depositing the precursor and before the step of sulfurizing, the step of reacting including reacting the precursor film with Se.
12. The method according to claim 11 wherein the step of reacting includes heating the precursor layer to a temperature range of 200-500° C. in the presence of Se.
13. The method according to claim 12 wherein the heating takes place for a period that ranges from one minute to thirty minutes.
14. The method according to claim 12 wherein the step of sulfurizing includes heating the precursor film to a temperature range of 200-600° C. in the presence of S.
15. The method according to claim 14 wherein the heating takes place for a period that ranges from one minute to one hour.
16. The method according to claim 12 wherein the step of heating results in an incomplete reaction with Se that forms binary, ternary or quarternary compound phases of Se with Cu, In and Ga.
17. The method according to claim 16 wherein the step of sulfurizing results in an incomplete reaction with S that forms binary, ternary or quarternary compound phases of S with Cu, In and Ga.
18. The method according to claim 14 wherein the step of selenizing includes heating the sulfurized precursor layer to a temperature range of 400-575° C. in the presence of Se.
19. The method according to claim 18 wherein the heating of the sulfurized precursor layer takes place for a period that ranges from one minute to one hour.
20. The method according to claim 19 wherein the resulting S/(S+Se) molar ratio is less than 0.1.
21. The method according to claim 1 wherein the precursor film further includes Se.
22. The method according to claim 21 wherein the Se/Cu molar ratio in the precursor layer is less than or equal to 1.6.