Low interface noise of p-GaN gate normally-off HEMT with microwave ohmic annealing process

In this work, a high-performance AlGaN/GaN normally-off p-gallium nitride (GaN) gate high electron mobility transistor (HEMT) was fabricated through low-temperature microwave annealing (MWA) in an ohmic metal alloy process. Compared with the conventional high-temperature rapid thermal annealing (RTA) process, MWA results in simultaneously superior ohmic contact and wafer sheet resistance because of the superior surface morphology of ohmic metal alloys. Moreover, Mg out-diffusion can be prevented through low-temperature MWA processes. The MWA p-GaN gate HEMT exhibited a maximum drain current density (I_Dmax) of 363 mA/mm with a threshold voltage (V_TH) of +1.6 V, a low subthreshold swing slope of 85 mV/dec, and a static on-resistance (R_ON) of 10.2 Ω·mm. The low frequency noise (LFN) and pulsed I–V indicated suppression of Mg out-diffusion, which could have induced extra traps in the device channel had it not been suppressed.