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Keywords:

  • GaN;
  • AlGaN/GaN;
  • HFET;
  • nonpolar;
  • a-plane;
  • current collapse

Abstract

We 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)