Field-dependent carrier trapping induced kink effect in AlGaN/GaN high electron mobility transistors

An anomalous kink effect featuring an abrupt recovery of drain current following current collapse is observed in the room-temperature output characteristics of AlGaN/GaN high electron mobility transistors. The kink is largely caused by trapping electrons from the gate leakage current by deep levels within the AlGaN barrier at high drain bias, resulting in a positive shift in threshold voltage and a reduction in reverse gate leakage current. The release of the trapped electrons is likely due to impact ionization of traps by hot electrons, which starts to play a role at relatively lower drain bias. Both sub-bandgap illumination and temperature rise could reduce the kink. (C) 2011 American Institute of Physics. [doi:10.1063/1.3584861]