Band alignment of Zn0.778Cd0.222O/MgO(0 0 1) heterointerface determined by X-ray photoelectron spectroscopy

Ternary Zn0.778Cd0.222O thin film oriented along c-axis has been successfully deposited on cubic MgO(0 0 1) substrate by pulsed laser deposition and no detectable phase separation at this concentration. The band offset properties at the interface of the Zn0.778Cd0.222O/MgO(0 0 1) heterojunction has also been experimentally studied by X-ray photoelectron spectroscopy. The valence-band offset is determined to be 4.67±0.30 eV. The heterojunction shows type-I band configuration with a conduction-band offset of 0.25±0.35 eV by using the experimental bandgaps of 2.91±0.05 eV for Zn0.778Cd0.222O and 7.83 eV for MgO. The value for conduction-band offset (0.25 eV) is lower than that of valence-band offset (4.67 eV), suggesting that transport is mainly dominated by electrons. The accurate determination of the band alignment of Zn0.778Cd0.222O/MgO heterojunction facilitates the design of optical and electronic devices based on Zn0.778Cd0.222O/MgO structure.