Enhanced gm and fT With High Johnson’s Figure-of-Merit in Thin Barrier AlGaN/GaN HEMTs by TiN-Based Source Contact Ledge

A high combination of transconductance(g_m), current gain cutoff frequency (f_T) and three terminal breakdown voltage was achieved using thin barrier AlGaN/GaN HEMTs and TiN-based source contact ledge. The sheet resistance is effectively reduced, whereas the peak extrinsic trans-conductance is improved by 24% from 334 to 415 mS/mm. The thin barrier AlGaN/GaN HEMTs with TiN-based source ledge exhibit a maximum drain current of 1096 mA/mm, a three-terminal off-state breakdown voltage (BVDS) of 151 V, a high current-gain cutoff frequency f_T of 69 GHz, and a high power-gain cutoff frequency f_MAX of 110 GHz. No significant drain current collapse was observed on thin barrier AlGaN/GaN HEMTs with TiN-based source contact ledge. The uniform fT characteristic over a wide range of bias condition is achieved by using the TiN-based source contact ledge devices. The calculated Johnson's figures of merit (J-FOM = BVGD×f_T) is 10.4 THz-V, which is the highest record so far for 0.2μm T-gate SiN passivation AlGaN/GaN HEMTs without source field plate.