Optical characterization of ZnO and ZnMgO films on a-plane sapphires by molecular beam epitaxy

Recently the growth techniques of single-crystalline ZnO film promote much attention to ZnO-related materials for electronic and optoelectronic applications. ZnO and ZnMgO films were grown by radical-source molecular beam epitaxy, and the epilays on a-plane sapphire substrates had a superior quality in crystallographic, optical and electrical properties. The surface during growth was monitored by a reflection high-energy electron diffraction (RHEED) system. After the growth, these films were characterized by Field emission scanning electronic miroscopy, transmission spectrum, photoluminescence (PL) using 325 rim line of a He-Cd laser, and electrical properties were measured by Hall measurement. The n-type doping with Al was successfully performed up to 5 X 10(19) cm(3). Widening of bandgap energy by increasing Mg composition was observed by transmission spectrum.