Self-induced photoionization of traps in buffer-free AlGaN/GaN HEMTs

Detrapping mechanisms and their dependence on applied bias have been studied in buffer-free AlGaN/GaN HEMTs on SiC. It is shown that the detrapping time constant decreases by orders of magnitude when the device is biased in semi-on conditions, or if the gate Schottky junction is forward biased with source and drain at ground. Despite completely different mechanisms are involved concerning charge transport and light emission, both bias conditions induce emission of high-energy photons (E>2 eV) which can photoionize traps, thus enhancing the recovery process. Data shown here suggest that a realistic description of GaN device behaviour can only be achieved by including optical effects in device modeling.