Self-aligned AlGaN/GaN high electron mobility transistors with 0.18 µm gate-length

To complement the gate scaling of HEMTs and also to reduce access resistance, self-aligned devices with a gate-length of 0.18 µm have been fabricated on 6H-SiC substrates using a single-step ohmic process. An Mo/Al/Mo/Au-based ohmic contact, requiring annealing temperatures around ∼550°C, was utilised. These 0.18 µm devices exhibited maximum drain current density of 900 mA/mm at a gate bias of 0 V and a drain bias of 10 V. The knee voltage was less than 2 V, showing the excellent nature of the ohmic contact. A peak extrinsic transconductance (gm) of 290 mS/mm was measured at Vgs=−2.6 V and a drain bias of 8 V. A unity gain cutoff frequency, fT of 92 GHz, and unilateral power gain frequency, fmax, were measured on these devices.