Morphology and electronic states of chemically treated CdZnTe surfaces

Abstract

The morphology and electronic structure of chemically treated CdZnTe surfaces has been studied using atomic force microscopy and scanning tunneling microscopy/spectroscopy. Studies have been performed on wet chemically etched and passivated surfaces. Etching in bromine methanol solutions effectively removes surface damage after polishing and produces a hillock like structure. A number of surface electronic states are introduced, both donor-like and acceptor-like, and are attributed to various surface defects. Because of the amorphous nature of the surface, these states have tails that extend into the band gap and produces a very narrow surface band. Charge hopping across the narrow band gap is proposed to explain the high surface conductivity. Surfaces passivated in hydrogen peroxide show increased roughness and using atomic force microscopy, the evolution of the formation of an oxide layer has been observed. Additional acceptor-like surface states of higher energy are introduced and the surface band gap is found to increase, reducing the surface conductivity.