Gallium doping dependence of single-crystal n-type Zno grown by metal organic chemical vapor deposition

High-quality single-crystal Ga-doped ZnO films have been epitaxially deposited on (0 0 0 2) sapphire substrate by low-pressure metal organic chemical vapor deposition (MOCVD) technique. The dependence of structural, electrical and optical properties of films on Ga doping concentration was investigated. As grown at the Ga/Zn gas ratio of 3.2 at%, the film shows a narrow linewidth of 0.26° for ZnO (0 0 0 2) peak, high carrier concentration of 2.47×1019 cm−3, and high optical transparency over 90%. The carrier concentration increased sharply and became saturated at higher doping level due to the onset of carrier compensation. The Burstein-Moss blueshift of the absorption edge energy increased as expected with the carrier concentration up to 2.47×1019 cm−3. In addition, doping-induced photoluminescence (PL) emission linewidth broadening and bandgap renormalization (BGR) effects have also been observed. The intensity of PL emission decreased with increasing Ga dopant concentration, which was believed to be a direct consequence of the doping-enhanced nonradiative recombination rates.