High-temperature enhancement mode operation of n-channel GaN MOSFETs on sapphire substrates

The high-temperature operation of a GaN MOSFET is reported. The MOSFETs were operated up to 250 °C, best reported to date. The MOSFETs showed good dc characteristics with field-effect mobilities of 138 cm2/Vs and 133 cm2/Vs at room temperature and 250 °C, respectively. The field-effect mobility, threshold voltage, and sub-threshold slope did not changed significantly up to 250 °C. Also, we compared the activation annealing condition for n+ layer fabrication. A high-temperature annealing condition of 1300 °C led to a low contact resistance, but caused slight degradation of the field-effect mobility compared with the 1100 °C annealing condition.