The chemical states of As 3d in highly doped ZnO grown by Molecular Beam Epitaxy and annealed in different atmospheres

Abstract

Arsenic doped ZnO films were grown by plasma assisted molecular beam epitaxy and post-growth annealed at 700°C in oxygen, nitrogen or argon atmosphere. The high resolution X-ray photoelectron spectroscopy (XPS) studies of the ZnO:As films revealed that the As3d core level spectra is formed by three components located at about 41eV, 44.5eV and 45.5eV below the Fermi level which we ascribe to AsO, AsZn‐2VZn and AsZn, respectively. The relative intensity of the three XPS contributions strongly depends on an annealing atmosphere, but in any case none of the contributions clearly dominates, which is a fingerprint of complicated nature of arsenic states in ZnO. This conclusion is also confirmed by the temperature dependent photoluminescence (PL) studies. Differences in the dominant PL peak positions and in their relative intensities are present and suggest different acceptor states in the examined samples.