GaN/VO2 heteroepitaxial p-n junctions: Band offset and minority carrier dynamics

Abstract

We report on experimental realization of p-n heterojunctions based on p-type GaN, and an n-type correlated oxide, VO2. The band offsets are evaluated by current-voltage and capacitance-voltage measurements at various temperatures. A band diagram based on the conventional band bending picture is proposed to explain the evolution of the apparent barrier height from electrical measurements and it suggests that the work function of VO2 decreases by ∼0.2 eV when it goes through the insulator to metal transtion, in qualitative agreement with Kelvin force microscopy measurements reported in literature. The frequency-dependent capacitance measurements allow us to differentiate the miniority carrier effect from the interface states and series resistance contributions, and estimate the minority carrier lifetime in insulating phase of VO2 to be of the order of few microseconds. The nitride-oxide based p-n heterojunctions provide a new dimension to study correlated-electron systems and could be of relevance to emerging electronic devices that exploit collective phenomena.