At pulse laser pumping, stimulated emissions are observed in ZnxMg1-xO epilayers. Among them, spectral blue shifts are
dependent on the Mg substitution concentration; and the highest lasing photon energy (in ZnO series materials even
reported) of 3.51 eV is observed. Furthermore, experimental results also show that by high concentration Mg
substitution, a red shift of the electron-hole plasma stimulated emission is reduced and its efficiency doesn't decrease
with the Mg substitution concentration. These results imply that the lasing frequency of ZnO series materials can be
modified by substitution. Secondly, lasing with low threshold in a closed micro-cavity filling with high scattering and
irregular structure gain medium is observed. Furthermore, the usual laser physics and random laser can't explain the
sharp bandwidth of lasing in sub-micron ZnO micro-crystals; a new concept of lasing needs to be proposed, which is
important to the develop in physics of carrier and lasing.
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 nm 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 × 1019 cm-3. Widening of bandgap energy by increasing Mg composition was observed by transmission spectrum.