Creation of current collapse in GaN HEMTs due to short-term DC bias stress

Summary form only given. Gallium nitride HEMTs have recently received significant attention for microwave high-power solid state applications, and have demonstrated record output power densities. Significant work is still required, however, for GaN HEMTs to become a viable technology. One area of current investigation is that of device stability. In the work reported here, we studied the effect of short term bias on the DC characteristics of several GaN HEMT wafers. A current collapse effect was found to be induced in some, but not all, of the devices after stress, apparently caused by the generation of trapping centers. This effect was observed for material grown by both MOCVD and MBE; and for a limited number of devices, it appears that silicon nitride passivation can suppress this effect.