Self-compensation induced high-resistivity in MgZnO

The degradation of conductivity with increased Mg content for Mg_xZn_1−xO wide bandgap materials has always been a fundamental application-motivated research issue. Herein, the study of self-compensating defects in Mg_xZn_1−xO:F (0  ⩽  x  ⩽  0.29) thin films was performed to reveal their influence on increased resistivity. Our observations solidly evidence that the degradation of conductivity is mainly owing to the increased concentration of Zn vacancy (V _Zn)-related compensating defects in Mg_xZn_1−xO alloys. The formation enthalpy of intrinsic V _Zn defects decreases as Mg content (x) increases. Thus, the compensation ratio increases from 0.23 at x  =  0 to 0.47 at x  =  0.29, resulting in deteriorated conductivity in Mg_xZn_1−xO alloys. Cathodoluminescence (CL) spectra further confirm higher V _Zn concentrations with increased Mg content. The electron transport is demonstrated to be dominated by an ionized scattering mechanism. Formation of $F_{\text{O}}^{+}$–$V_{\text{Zn}}^{2-}$ complexes could reduce the concentration of ionized scattering centers and thus increase mobility. These results clarify the reason of increasingly high resistivity in Mg_xZn_1−xO, which is a long-sought-after physics problem in this area, and provide crucial information on controlling the conductivity of Mg_xZn_1−xO alloys. (paper)