Atomic layer etching (ALE) of III-nitrides
Wan Ying Ho, Yi Chao Chow, Zachary J. Biegler, Kai Shek Qwah, Tanay Tak, Ashley Wissel-Garcia, I.-S. Liu, Feng Wu, Shuji Nakamura, James S. Speck
Abstract
Atomic layer etching (ALE) was performed on (Al, In, Ga)N thin films using a cyclic process of alternating Cl2 gas absorption and Ar+ ion bombardment in an inductively coupled plasma etcher system. The etch damage was characterized by comparing photoluminescence of blue single quantum well light-emitting diodes before and after the etch as well as bulk resistivities of etched p-doped layers. It was found that etched surfaces were smooth and highly conformal, retaining the step-terrace features of the as-grown surface, thus realizing ALE. Longer exposures to the dry etching increased the bulk resistivity of etched surfaces layers slightly, with a damaged depth of ∼55 nm. With further optimization and damage recovery, ALE is a promising candidate for controlled etching with atomic accuracy. It was found that Al0.1Ga0.9N acts as an etch barrier for the ALE etch, making it a suitable etch to reveal buried V-defects in III-nitride light emitting diodes.