Enhanced gmand fTWith High Johnson’s Figure-of-Merit in Thin Barrier AlGaN/GaN HEMTs by TiN-Based Source Contact Ledge

Abstract

A high combination of transconductance ( $\text{g}_{\text {m}}$ ), current gain cutoff frequency ( $\text{f}_{\text T}$ ) 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 (BV $_{\textsf {DS}}$ ) of 151 V, a high current-gain cutoff frequency $\text{f}_{\text T}$ of 69 GHz, and a high power-gain cutoff frequency $\text{f}_{\text {MAX}}$ of 110 GHz. No significant drain current collapse was observed on thin barrier AlGaN/GaN HEMTs with TiN-based source contact ledge. The uniform $\text{f}_{\text T}$ 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 = BV $_{\textsf {GD}}\times \text{f}_{\text T}$ ) is 10.4 THz-V, which is the highest record so far for $0.2\mu \text{m}$ T-gate SiN passivation AlGaN/GaN HEMTs without source field plate.