Deeply-scaled self-aligned-gate GaN DH-HEMTs with ultrahigh cutoff frequency

We report record DC and RF performance in deeply-scaled self-aligned gate (SAG) GaN-HEMTs operating in both depletion-mode (D-mode) and enhancement-mode (E-mode). Through aggressive lateral scaling of the gate length (L_g) and the source-drain distance (L_sd) using a novel self-aligned gate technology and engineering of a thin top barrier layer, 20-nm gate AlN/GaN/AlGaN double-heterojunction (DH) HEMTs operating in D-mode (and E-mode) exhibited record DC and RF characteristics with high yield and uniformity; R_on = 0.29 (0.33) Ω·mm, I_dmax = 2.7 (2.6) A/mm, a peak extrinsic g_m = 1.04 (1.63) S/mm, threshold voltage uniformity σ (V_th) = 44 (63) mV over a 3-inch wafer area, and a simultaneous f_T/f_max = 310/364 (343/236) GHz. Delay time analysis clarified that an unique dependence of f_T on V_ds resulted from suppressed drain delay and enhanced electron velocity due to the lateral source-drain (S-D) scaling.