AlGaN/GaN based MOSHFETs with Different Gate Dielectrics and Treatments

AlGaN/GaN based hetero field effect transistors (HFETs) were capped with different dielectrics, characterized, and tested for DC performance. As dielectrics we use SiO 2 and photoelectrochemical (PEC) grown Al x Ga 2-x O 3 . Combination of this two dielectrics show best performance with respect to gate leakage current and controllability of the drain current ID. TheMOSHEFTs work also at positive gate voltages in accumulation, which is also demonstrated in a broad transconductance peak. The PEC oxidation shows low density of interface states D it and the insulating properties depend strongly on the PEC conditions. Pre-treatments before the SiO 2 deposition result in varying threshold voltages |Vth| and it seems that (NH 4 )Sx pre-treatment leaves the surface in best conditions. Comparison of Ti/Al and Ti/Al/Ti/Au as source/drain contacts for AlGaN/GaN HFETs are done and the annealing behavior of Ti/Al/Ti/Au is displayed resulting in contact resistance as low as RC = 2 &mm after annealing at 850°C in N 2 .