Structural, optical, and electronic properties of MgxZn1-xO (0 ≤ x ≤ 0.38) films pseudomorphically grown on Zn-polar ZnO substrates

Abstract

ZnO is a typical oxide semiconductor with a wide direct band gap of 3.37 eV and offers a variety of possibilities for optical and electronic applications. Alloying with Mg into the Zn site increases the band gap, enabling band engineering. In this study, we have performed comprehensive characterizations of Mg_xZn_1-xO thin films grown on Zn-polar ZnO substrates, which are of particular importance because of the excellent quality compared with those grown on other substrates such as Al₂O₃. We have obtained Mg content dependence of optical constants, two-dimensional carrier density, and valence band and core-level energies. These results indicate that, while the optical property is determined solely by the Mg content in the bulk, local structure, and Mg distribution can have a significant influence on the interface and surface properties.