Self-aligned AlGaN/GaN high electron mobility transistors

Self-aligned T-gate AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated on a sapphire substrate using a thin Ti/Al/Ti/Au ohmic layer. To suppress the gate leakage current, the ohmic contact annealing was performed in a furnace. The self-aligned HEMTs with 0.25 (mu)m gate length and 100 (mu)m width exhibit good pinch-off characteristics, a transconductance of 146 mS/mm, an extrinsic unity current gain cutoff frequency of 38 GHz and a maximum oscillation frequency of 130 GHz.