Optical and electrical properties of gallium-doped Mg(x)Zn(1-x)O.

In this study, the optical and electrical properties of epitaxial single crystal gallium-doped Mg(x)Zn(1-x)O thin films grown on c-plane sapphire substrates by pulsed laser deposition were investigated. In these films, the Ga content was varied from 0.05 to 7 at. % and the Mg content was varied from 5 to 15 at. %. X-ray diffraction showed that the solid solubility limit of Ga in Mg(x)Zn(1-x)O is less than 3 at. %. The absorption spectra were fitted to examine Ga doping effects on bandgap and band tail characteristics. Distinctive trends in fitted bandgap and band tail characteristics were determined in films with Ga content below 3 at. % and Ga content above 3 at. %. The effects of bandgap engineering on optical transparency were evaluated using transmission spectra. Carrier concentration and Hall mobility data were obtained as functions of Ga content and Mg content. The electrical properties were significantly degraded when the Ga content exceeded 3 at. %. Correlations between conduction mechanisms and gallium doping of Mg(x)Zn(1-x)O thin films were described. In addition, the effect of bandgap engineering on the electrical properties of epitaxial single crystal gallium-doped Mg(x)Zn(1-x)O thin films was discussed.