Depth-resolved electronic structure measurements by hard X-ray photoemission combined with X-ray total reflection: Direct probing of surface band bending of polar GaN

We have developed high-throughput depth-resolved electronic structure measurements using hard X-ray photoelectron spectroscopy (HAXPES) combined with X-ray total reflection (TR). By utilizing a steep change of the X-ray attenuation length around the TR condition, we controlled the effective inelastic mean-free-path of photoelectrons from similar to 2 to similar to 12nm in HAXPES. We applied this method to probe the surface band bending of n-type polar GaN and found the different band bending behaviors in the Ga- and N-polar surfaces. This result is related to the surface contaminations and crystal quality near the surfaces of polar GaN. (C) 2018 The Japan Society of Applied Physics.