High-Efficiency Millimeter-Wave Enhancement-Mode Ultrathin-Barrier AlGaN/GaN Fin-HEMT for Low-Voltage Terminal Applications
Yuwei Zhou, Minhan Mi, Can Gong, Pengfei Wang, Xinyi Wen, Yilin Chen, Jielong Liu, Mei Yang, Meng Zhang, Qing Zhu, Xiaohua Ma, Yue Hao
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.