Physics-Based Explanation of Kink Dynamics in AlGaAs/GaAs HFETs

The physical origin of the kink and its dynamics are investigated in AlGaAs/GaAs doped-channel heterostructure field-effect transistors (HFETs) both through measurements and two-dimensional (2-D) device simulations. The kink is shown to arise from the interaction of surface deep acceptors with impact-ionization-generated holes, the latter partially discharging the deep levels and therefore leading to conductive-channel widening and to drain-current increase. Under pulsed operation, kink dynamics is governed by hole emission, and capture phenomena, prevailing at low and high drain-source voltages, respectively.