High-Efficiency Millimeter-Wave Enhancement-Mode Ultrathin-Barrier AlGaN/GaN Fin-HEMT for Low-Voltage Terminal Applications

Abstract

In this work, high-efficiency millimeter-wave enhancement-mode (E-mode) Fin-high electron mobility transistor (HEMT) is fabricated to satisfy low-voltage terminal applications, whose fabrication process is performed on the in situ SiN passivated ultrathin-barrier AlGaN/GaN heterojunction and features N2O plasma oxidation treatment on the fins. Specifically, the fabricated E-mode Fin-HEMT exhibits a positive threshold voltage of 0.3 V, at the cost of decreased maximum output current density of 483 mA/mm and lowered peak extrinsic transconductance of 277 mS/mm. Comfortingly, a reduced knee voltage of 1.5 V together with suppressed OFF-state leakage current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6\times 10^{-{6}}$ </tex-math></inline-formula> mA/mm is also obtained for Fin-HEMT. Besides, an OFF-state breakdown voltage of 38 V is achieved, which is sufficiently high to meet the low-voltage RF device’s need for breakdown voltage. Pulsed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> measurement shows that a negligible current collapse (CC) is achieved for Fin-HEMT. Additionally, Fin-HEMT demonstrates a good stability by stress reliability test. Subsequently, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{T}/{f}_{\text {MAX}}$ </tex-math></inline-formula> value of 40/86 GHz is obtained for Fin-HEMT at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {DS}}$ </tex-math></inline-formula> of 6 V by small signal measurement. Eventually, the millimeter-wave low-voltage load pull measurement shows that the fabricated E-mode Fin-HEMT is able to deliver a decent power added efficiency (PAE) of 55% at 30 GHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {DS}}$ </tex-math></inline-formula> of 6 V, revealing the great potential of the fin configuration combined with ultrathin-barrier AlGaN/GaN heterojunction passivated by in situ SiN and N2O plasma oxidation treatment in high-efficiency millimeter-wave low-voltage terminal applications.