High-Performance Enhancement-mode AlGaN/GaN high electron mobility transistors combined with TiN-based Source Contact Ledge and Two-Step Fluorine Treatment

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> ) 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 (@ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\text {GS}} =3$ </tex-math></inline-formula> V), a threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\text {th}}$ </tex-math></inline-formula> ) of 0.6 V, a high current-gain cutoff frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{\text {T}}$ </tex-math></inline-formula> of 61 GHz, and a high power-gain cutoff frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{\text {MAX}}$ </tex-math></inline-formula> 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 = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{BV}_{\text {DS}}\times {f}_{T}$ </tex-math></inline-formula> ) is 11.2 THz-V, the highest so far for GaN-based HEMTs. The calculated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {BV}_{\text {DS}} \times {f}_{\text {MAX}}$ </tex-math></inline-formula> value is 23.8 THz-V, indicating significantly improved the speed and power performance of the E-mode GaN-based HEMT.