High-Performance Enhancement-Mode AlGaN/GaN High Electron Mobility Transistors Combined With TiN-Based Source Contact Ledge and Two-Step Fluorine Treatment

High performance enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) were achieved by using the TiN-based source contact ledge and two-step fluorine treatment. Due to the effective reduction of the source resistance by TiN-based source contact ledge, the peak extrinsic trans-conductance improved by 21.2% from 340 to 412 mS/mm. In addition, due to the enhancement of the back barrier by the two-step fluorine treatment, the three-terminal OFF-state breakdown voltage (BV
_DS
) improved by 11.5% from 162 to 183 V. The proposed E-mode AlGaN/GaN HEMTs exhibit a maximum drain current of 845 mA/mm (@
${V} _{\text {GS}} =3$
V), a threshold voltage (
${V} _{\text {th}}$
) of 0.6 V, a high current-gain cutoff frequency
${f} _{\text {T}}$
of 61 GHz, and a high power-gain cutoff frequency
${f} _{\text {MAX}}$
of 130 GHz. Approximately 5% current collapse occurs at a drain quiescent bias of 30 V. The calculated Johnson’s figure of merit (J-FOM =
$\text{BV}_{\text {DS}}\times {f}_{T}$
) is 11.2 THz-V, the highest so far for GaN-based HEMTs. The calculated
$\text {BV}_{\text {DS}} \times {f}_{\text {MAX}}$
value is 23.8 THz-V, indicating significantly improved the speed and power performance of the E-mode GaN-based HEMT.