Photoelectrochemical etching of P-type semiconductor heterostructures
View Patent ↗A method for photoelectrochemical (PEC) etching of a p-type semiconductor layer simply and efficiently, by providing a driving force for holes to move towards a surface of a p-type cap layer to be etched, wherein the p-type cap layer is on a heterostructure and the heterostructure provides the driving force from an internal bias generated internally in the heterostructure; generating electron-hole pairs in a separate area of the heterostructure than the surface to be etched; and using an etchant solution to etch the surface of the p-type layer.
1. A method for etching a p-type semiconductor layer in a device structure, comprising:
photo-electrochemical (PEC) etching the p-type layer of a p-i-n heterostructure using an internal electric field of the device structure and an electrolyte.
2. The method of claim 1 , wherein the internal electric field drives holes to a surface of the p-type layer being etched.
3. The method of claim 1 , further comprising generating electron-hole pairs in a separate area of the device structure than a surface of the p-type layer being etched, wherein the internal electric field provides a driving force for holes to move towards the surface, rather than a bulk, of the p-type layer.
4. The method of claim 3 , further comprising photo-generating the electron hole pairs with light from a light source, and selecting the light's frequency such that the light is only absorbed in the separate area of the device structure where the internal electric field is located.
5. The method of claim 1 , wherein the internal electric field is generated internally inside the heterostructure.
6. The method of claim 1 , wherein substantially no external bias is applied to the p-type layer in order to etch the p-type layer.
7. The method of claim 1 , wherein the internal electric field is stronger, thereby bringing holes to a surface of the p-type layer faster, as compared to an electric field produced by an external bias applied to the device structure in order to etch the p-type layer.
8. The method of claim 1 , wherein the internal electric field enables etching the p-type layer at a rate at least comparable to an etch rate of an n-type layer.
9. The method of claim 8 , wherein the etch rate is at least 2.8 nm per minute, an external bias is less than 2 Volts, and the etching produces a surface roughness of the p-type layer at least as smooth as a surface roughness of an n-type layer etched under substantially similar conditions.
10. The method of claim 1 , further comprising etching the p-type layer in an electrolyte at room temperature.
11. The method of claim 1 , further comprising etching the p-type layer in an electrolyte at a temperature lower than a temperature used in a chemical wet etch of the p-type layer, or at the temperature lower than a temperature used in an etch of the p-type layer that uses an external bias.
12. The method of claim 1 , further comprising etching the p-type layer to obtain surfaces that are not crystallographic planes.
13. The method of claim 1 , further comprising etching one or more anisotropic trenches in the p-type layer.
14. The method of claim 1 , further comprising etching the p-type layer with bandgap selectivity, defect selectivity, or both bandgap selectivity and defect selectivity.
15. The method of claim 1 , wherein the etching is wet etching.
16. The method of claim 1 , further comprising doping the device structure to create the internal electric field that drives holes to a location of the device structure being etched.
17. The method of claim 1 , further comprising introducing strain into the device structure to create the internal electric field that drives holes to a location of the device structure being etched.