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Keywords:

  • AlGaN/GaN;
  • HEMT;
  • multi-mesa-channel (MMC);
  • current collapse

Abstract

Transport properties and off-stress-induced current collapse characteristics of the multi-mesa-channel (MMC) AlGaN/GaN HEMTs were investigated. The surrounding field effect in the MMC structure led to a shallower threshold voltage and a smaller subthreshold slope compared to those of the conventional planar HEMT. After applying off-state bias stress, the planar HEMT showed remarkable current collapse, including significant increase in on-resistance increasing the drain stress bias. On the other hand, for the MMC HEMT, we observed less change in on-resistance (RON) even after the application of high drain bias stress. This shows that the MMC structure has resistance to the off-stress-induced current collapse. In the case of a mesa-top width (Wtop) of less than 100 nm, the channel resistance of the MMC HEMT is estimated to be about one order of magnitude higher than the increase in access resistance induced by the off-state stress. It is thus likely that the operation of the MMC HEMT is rather insensitive to change in access resistance. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)