Bandgap and band edge positions in compositionally graded ZnCdO

Introducing Cd into ZnO allows for bandgap engineering, potentially with particularly interesting properties to observe in compositionally graded samples. In this work, compositionally graded Zn1-xCdxO samples with 0 <= x <= 0.16 were made using metal organic vapour phase epitaxy. The chemical composition was studied using scanning transmission electron microscopy, while the band structure of the samples was investigated using a combination of cathodoluminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). It is found that the reduction of the bandgap in our samples is caused by changes in the conduction band. The position of the Fermi level relative to the vacuum level, i.e., the workfunction, was also found to change upon addition of Cd, giving an apparent shift in the valence band when evaluated from the XPS valence spectra. Published by AIP Publishing.