In situ and selective area etching of GaN by tertiarybutylchloride (TBCl)

Abstract

In situ etching (ISE) of gallium nitride (GaN) can enable lateral and vertical junctions through selective area etching (SAE) and regrowth. We report the study of ISE and SAE of GaN using an organometallic precursor, tertiarybutylchloride (TBCl), in a metal-organic chemical vapor deposition reactor. Compared to the conventional etching in hydrogen, the use of TBCl allows in situ etching at a much lower temperature (<850 °C), likely due to a more reactive etchant and a more efficient desorption rate of the etching products. The TBCl etching is near equilibrium and can be significantly changed with the change of the NH3 flow rate. We also report initial results of SAE on SiO2 patterned GaN samples. An important finding is the need to control the desorption of the reaction products in order to achieve smooth surfaces. TBCl etching is crystallographically anisotropic with low etch rates on N-terminated facets. The use of TBCl and possibly other organometallic halogen precursors is expected to enable the design and implementation of III-nitride lateral junction devices that have not been possible.