Spectroscopic analysis of the epitaxial CaO (111)-GaN (0002) interface

We report an x-ray photoelectron spectroscopy (XPS) study of the CaO/GaN interface. Epitaxial films of CaO (111) were grown on GaN (0002) and analyzed in situ using XPS. We observe Stranski-Krastanov growth, in which CaO coalesces rapidly, then converts to a three-dimensional mode. Data suggest coalescence within the first nanometer of film growth, indicating growth behavior different from published reports of the analogous MgO-GaN system. We find 1.0 +/- 0.2 eV for the valence band offset and a 2.5 +/- 0.2 eV conduction band offset. The results are discussed in terms of their utility in oxide-nitride electronic devices. (c) 2008 American Institute of Physics.