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

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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742172]