The fabrication of recessed gate GaN MODFET's

MODFET's were fabricated on GaN/Al_0.27Ga_0.73N heterostructure, with and without a gate recess etch. ECR etching was utilized for the gate recess and did not introduce any noticeable damage. After the recess etch, the peak g_m improved from 23mS/mm to 47mS/mm. At the gate lengths of 0.25μm, f_t of 11GHz and f_max of 21GHz were measured for non-recessed gates. For 0.4μm recessed gates, f_t of 14GHz and f_max of 42.5GHz were achieved. Through the subsequent annealing alter the proton bombardment, a severe degradation of the electrical isolation was observed, showing more than factor of 600 reduction of resistance with 450°C 15sec anneal.