Method and apparatus for doping semiconductors
Semiconductor materials such as silicon particles are doped by mixing the semiconductor material with a solution having a dopan and a solvent. The solvent is removed from the wetted surface of the particles of the semiconductor material, thereby yielding particles that are substantially free from the solvent and are uniformly coated with the dopant.
1. A method for doping a semiconductor material, the method comprising:
mixing particles of a semiconductor material with a doping solution comprising a dopant and a solvent to form a mixture; and
heating the mixture to vaporize the solvent, thereby yielding particles of the semiconductor material which are substantially free from solvent and uniformly coated with the dopant.
2. The method of claim 1 wherein the mixture is heated to a temperature of between about 30° C. to about 110° C.
3. The method of claim 1 wherein the particles of the semiconductor material are silicon particles.
4. The method of claim 3 wherein the silicon particles are in the form of pellets.
5. The method of claim 3 wherein the silicon particles are in the form of angular irregularly shaped particles having sizes up to 1 cm in diameter.
6. The method of claim 3 wherein the silicon particles are in the form of spherical particles.
7. The method of claim 1 wherein the dopant is one or more of a p-type dopant.
8. The method of claim 1 wherein the dopant is one or more of a Group III element.
9. The method of claim 1 wherein the dopant is one or more of a n-type dopant.
10. The method of claim 1 wherein the dopant is one or more of a Group V element.
11. The method of claim 1 wherein the solvent has a boiling temperature between about 40° C. and about 110° C.
12. A method for doping a semiconductor material for use in adding a dopant to a semiconductor melt, the method comprising the steps of:
a. applying a doping solution comprising the dopant and a solvent to particles of the semiconductor material to yield a feedstock material coated with the doping solution;
b. mixing the feedstock material to uniformly coat the particles of the semiconductor material with the doping solution; and
c. drying the coated feedstock material to evaporate the solvent, thereby leaving a coat of dopant on the surface of the feedstock material.
13. The method of claim 12 further comprising the step of:
d. melting the dried coated feedstock material to form a mixture of semiconductor material and the dopant.
14. The method of claim 13 wherein the mixture comprises a concentration of dopant sufficient to provide the desired doping level; 0.01 to 20 ohm-cm n-type or p-type material.
15. The method of claim 13 further comprising the step of:
e. feeding the melted mixture into a crucible to grow a crystal ribbon.
16. The method of claim 12 wherein step c comprises applying heat to the coated feedstock material.
17. The method of claim 12 wherein step c comprises applying a vacuum to the coated feedstock material.
18. The method of claim 12 wherein step c comprises blow-drying the feedstock material.
19. The method of claim 12 wherein the particles of the semiconductor material are silicon particles.
20. The method of claim 12 wherein the dopant is one or more of a p-type dopant.
21. The method of claim 12 wherein the dopant is one or more of a Group III element.
22. The method of claim 12 wherein the dopant is one or more of a n-type dopant.
23. The method of claim 12 wherein the dopant is one or more of a Group V element.
24. The method of claim 12 wherein the solvent is a low boiling point alcohol.