The Physics of Reliability for High Voltage AlGaN/GaN HFET's

High voltage HFET's fabricated from nitride semiconductors utilizing the AlGaN/GaN heterojunction demonstrate excellent RF performance with RF output power greater than an order of magnitude higher than available from GaAs and InP based devices. However, the nitride devices demonstrate a reliability problem where the dc current and RF output power continually decrease as a function of time. The reliability problem is related to the conduction characteristics of the gate electrode and an electron tunneling mechanism where electrons leak from the gate to the surface of the semiconductor. In this work the physics responsible for this behavior are investigated and described