Self-aligned-gate GaN-HEMTs with heavily-doped n+-GaN ohmic contacts to 2DEG

Abstract

We report record DC and RF performance obtained in deeply-scaled self-aligned-gate GaN-HEMTs with heavily-doped n⁺-GaN ohmic contacts to two-dimensional electron-gas (2DEG). High density-of-states of three-dimensional (3D) n⁺-GaN source near the gate mitigates “source-starvation,” resulting in a dramatic increase in a maximum drain current (I_dmax) and a transconductance (g_m). 20-nm-gate D-mode HEMTs with a 40-nm gate-source (and gate-drain) distance exhibited a record-low R_on of 0.23 Ω·mm, a record-high I_dmax of >4 A/mm, and a broad g_m curve of >1 S/mm over a wide range of I_ds from 0.5 to 3.5 A/mm. Furthermore, 20-nm-gate E-mode HEMTs with an increased L_sw of 70 nm demonstrated a simultaneous f_T/f_max of 342/518 GHz with an off-state breakdown voltage of 14V.