Thermal stability of rhenium Schottky contacts on n-type AlxGa1−xN

The impact of rapid thermal annealing on the electrical and materials characteristics of Re Schottky contacts on n-type GaN and AlxGa1−xN (x=0.10 and 0.26) was investigated. Effective barrier heights were obtained from current–voltage and modified Norde measurements on diodes annealed at up to 800 °C. For AlxGa1−xN with x>0, Schottky barrier heights were found to increase upon annealing from the as-deposited state, but decreased sharply after annealing at 600 °C. Modified Norde measurements indicate that this degradation could be explained by the existence of a shunt conduction path with an associated barrier height below 0.46 V, possibly a consequence of an inhomogeneous interface after annealing at temperatures above 600 °C. A new defect lying at 0.34 eV below the conduction band edge was also detected by deep level transient spectroscopy after contact degradation.