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

To complement the gate scaling of HEMTs and also to reduce access resistance, self-aligned devices with a gate-length of 0.18m 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 0.18m devices exhibited maximum drain current density of 900mA/mm at a gate bias of 0V and a drain bias of 10V. The knee voltage was less than 2V, showing the excellent nature of the ohmic contact. A peak extrinsic transconductance (g_m) of 290mS/mm was measured at V_gs=-2.6V and a drain bias of 8V. A unity gain cutoff frequency, f_T of 92GHz, and unilateral power gain frequency, f _max, were measured on these devices.