Direct demonstration of the 'virtual gate' mechanism for current collapse in AlGaN/GaN HFETs

Potential probes to the channel of a long channel AlGaN/GaN HFET are used to directly measure the increase in resistance of the ungated regions at the source and drain that are responsible for current collapse under pulsed conditions. Silicon nitride passivation is shown to be an effective means of preventing the formation of the 'virtual gate' on the ungated surface.