Band alignment and interfacial structure of ZnO/Ge heterojunction investigated by photoelectron spectroscopy

Studies on band-offset and band-alignment of heterojunction of highly c-axis oriented ZnO thin films grown on n-Ge (111) by pulsed laser deposition show a type-II band alignment with the valence band offset (Delta E-V) of 3.1 +/- 0.2 eV. The valence band spectra of this heterojunction show band onsets corresponding to Ge, interfacial GeOx, and ZnO layers. This observation also enabled us to determine Delta E-V of ZnO/GeOx heterojunction to be 1.4 +/- 0.2 eV. These studies provide further insight into the band alignment of ZnO/GeOx/Ge system wherein the observed large value of DEV of ZnO/Ge can be used for heterojunction based optoelectronic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767524]