Deep-recessed GaN HEMTs using selective etch technology exhibiting high microwave performance without surface passivation

A selective dry etch technology of GaN over AlGaN using BCl₃/SF₆ has been applied to passivation-free deep-recessed GaN HEMTs, significantly reducing the effects of growth and process variations on the device performance, improving reproducibility and manufacturability. The effects of Si delta-doping density on the gate leakage, breakdown voltage and dispersion were investigated. Excellent microwave power performances were achieved without SiN_x passivation. 6 W/mm with PAE of 72% at V_D= 30 V and 11.6 W/mm with PAE of 63% at V_D=50 V were demonstrated at 4 GHz, while 5 W/mm with PAE of 63% at V_D= 28 V and 10.5 W/mm with PAE of 53% at V_D=48 V were obtained at 10 GHz.