Influence of Growth Temperature on the Characteristics of Ga-Doped ZnO Thin Films Deposited by Magnetron Sputtering

概要

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Ga-dope ZnO (ZnO:Ga) thin films with n-type semiconducting behavior were grown on $c$-sapphire substrates by radio frequency magnetron sputtering at various growth temperatures. The room temperature grown ZnO:Ga film showed a slight preferred orientation along the $c$-axis with small domain size and high density of stacking faults. The increase in growth temperature from 300 to 550 °C resulted in the growth of granular shaped epitaxial ZnO:Ga films due to insufficient thermal energy and large lattice mismatch. The films grown at above 550 °C showed a flat surface with the simultaneous improvement of the electrical carrier concentration and carrier mobility ($6.3\times 10^{18}$/cm-3 and 27 cm2 V-1 s-1, respectively). In addition, there was an increase in the grain size and a decrease in the dislocation density in the high temperature grown films. The low-temperature photoluminescence of the ZnO:Ga films grown at ${<}450$ °C showed the redshift in deep-level emission, which was attributed to a transition from Zni to Oi level.
2009-08-25