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Keywords:

  • AlGaN/GaN;
  • HFETs;
  • electrical properties;
  • performance

Abstract

High-voltage microwave AlGaN/GaN HFETs operating under high-power conditions suffer from degraded RF performance and linearity due to a nonlinear resistance effect in the gate-source region. During RF operation, the nonlinear resistance is due to the onset a of space-charge-limited current (SCLC) transport mechanism within the device channel. Under high current injection conditions, SCLC transport can set in and, consequently, the source resistance becomes a function of the injected charge causing a rapid increase and limiting device performance. The threshold for SCL current is dependent on the donor-like states on the AlGaN surface which are responsible for supplying electrons to the channel. To alleviate the effect of nonlinear source resistance we show on an un-gated HFET channel model that the critical current density of space-charge effects and thus the onset of nonlinear source resistance can be shifted above the normal operating current density of the device by modification of the charge on the AlGaN surface. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)