X-Ray Photoemission Investigation of the Beryllium Oxide Band Alignment with Magnesium Oxide and Estimates for Other Insulating and Conducting Oxides

Abstract

Beryllium oxide (BeO) is a wurtzite structured, large bandgap (E g > 8 eV) material of significant interest as an alloying agent and cladding dielectric in various wide band gap oxide based optoelectronic devices. The success of such devices is highly reliant on bandgap and band alignment engineering to achieve sufficient charge carrier and optical confinement for device operation. In this regard, we have utilized x-ray photoemission spectroscopy (XPS) to determine the valence band offset (VBO) between atomic layer deposited (ALD) BeO and a magnesium oxide (MgO) substrate with (001) orientation. The BeO VBO with MgO (001) was determined to be 0.1 ± 0.15 eV. Applying the rules of commutativity and transitivity for band alignment, we additionally predict the BeO VBO with other wide bandgap conductive oxides such as ZnO, Ga2O3, and InGaZnO4, to be 1.15 ± 0.3 eV, 0.3 ± 0.2 eV, and 0.9 ± 0.2 eV, respectively. Utilizing the reported bandgaps for ALD BeO and the conductive oxides, we find a Type I band alignment with CBOs > 1 eV in all cases. BeO is therefore a promising dielectric for oxide based optoelectronic and high-frequency, -power, and -temperature device applications