Low-frequency noise and current-transient measurements were applied to analyze the degradation of nearly latticematched InAlN/AlN/GaN heterostructure field-effect transistors caused by electrical stress. Almost identical devices on the same wafer were stresses 7 hr. at a fixed DC drain bias of V_DS=20 V and different gate biases. We noted up to 32 dB/Hz higher low-frequency noise for stressed devices over the entire frequency range of 1 Hz- 100 kHz. The measurements showed the minimum degradation at a gate-controlled two-dimensional electron gas density of 9.4x10¹² cm^-2. This result is in good agreement with the reported stress effect on drain-current degradation and current-gain-cutoff-frequency measurements, and consistent with the ultrafast decay of hot-phonons due to the phonon-plasmon coupling. Moreover, the current transient (gate-lag) measurements were also performed on pristine and highly degraded devices up to 5 ms pulse durations. Drain current is almost totally lost in degraded HFETs as opposed to a very small drop for pristine devices and no recovery observed for both indicating that generation of deep traps in GaN buffer.

Date Published: 27 February 2012
PDF: 7 pages
Proc. SPIE 8262, Gallium Nitride Materials and Devices VII, 82621W (27 February 2012); doi: 10.1117/12.908501

Published in SPIE Proceedings Vol. 8262:
Gallium Nitride Materials and Devices VII
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon, Editor(s)