Control of structure, conduction behavior, and band gap of Zn1−xMgxO films by nitrogen partial pressure ratio of sputtering gases

Abstract

Zn 1 − x Mg x O films were grown by radio-frequency reactive magnetron sputtering using mixture of nitrogen and argon as sputtering gases. It was found that Mg concentration, structures, electrical properties, and band gaps of the films can be tuned by changing nitrogen partial pressure ratio of the sputtering gases. The Zn1−xMgxO film consists of wurtzite phase at the ratios from 0% to 50%, mixture of wurtzite and cubic phases at the ratios of 78% to 83%, and cubic phase at 100%. The Mg concentration increased linearly with increasing the ratio. The band gap increases from 3.64eV at x=0.172to4.02eV at x=0.44 for the wurtzite Zn1−xMgxO and reaches 6.30eV for cubic Zn1−xMgxO with x=0.84. All the as-grown Zn1−xMgxO films show high resistivity at room temperature, but transform into p-type conduction after annealing at 600°C for 30min under 10−4Pa, except for the film grown at the ratio of zero.