Valence band offset of n-ZnO/p-MgxNi1−xO heterojunction measured by x-ray photoelectron spectroscopy

Abstract

The valence band offset (VBO) of a n-ZnO/p-MgxNi1−xO heterojunction grown by pulsed laser deposition was investigated by x-ray photoelectron spectroscopy. From the directly measured VBO of 1.64 ± 0.05 eV, a −2.26 ± 0.05 eV conduction band offset was derived. This indicates that the ZnO/MgxNi1−xO heterojunction has a type-II (staggered) band alignment. The conduction band minimum (CBM) of the n-ZnO/p-MgxNi1−xO heterojunction shifts to higher energy with Mg doping relative to the n-ZnO/p-NiO heterojunction. Thus, the position of the CBM can be controlled by the Mg concentration.