Small current collapse in AlGaN/GaN HFETs on a‐plane GaN self‐standing substrate

Abstract

AbstractWe measured drain bias stress effects and current collapse in AlGaN/ GaN heterostructure field‐effect transistors (HFETs) on a‐plane and c‐plane GaN substrates. An a‐plane AlGaN/GaN HFET (a‐HFET) shows small current collapse with a threshold voltage (Vth = ‐1.8 V). On the other hand, a c‐plane HFET (c‐HFET) with the same barrier thickness (20 nm) shows a small current collapse, although Vth was negatively large (Vth = ‐4 V).Current collapse in a‐HFET was not large compared with that in conventional c‐HFET on GaN. A c‐HFET on sapphire was also measured. The current collapses in HFETs on sapphire were larger than that in HFETs on a GaN substrate. The current collapses in the thin‐barrier c‐HFET (Vth = ‐1.8 V) were particularly large. Therefore, an a‐plane device is promising for a small or positive Vth with small current collapse. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)