Effects of RF and DC stress on AlGaN/GaN MODFETs: a low-frequency noise-based investigation

The impact of radio frequency (RF) and DC stress on passivated and unpassivated AlGaN/GaN modulation-doped field effect transistors (MODFETs) is investigated by means of DC and low-frequency noise (LFN) measurements. Unpassivated devices endure significant changes in the output resistance, gate, and drain noise current level after RF and DC stress. RF and DC stress of unpassivated devices leads to different degradation time constant and gate noise current. Besides, a positive shift in the pinch-off voltage is found to take place only after RF stress. In contrast to unpassivated devices, passivated devices do not show any considerable variation in the output resistance and gate, and drain noise current characteristics upon RF or DC stress. However, a positive shift in the pinch-off voltage upon RF stress is observed for both types of devices.