High RF Performance Enhancement-Mode Thin-Barrier AlGaN/GaN HEMTs on Si Substrate for Low-Voltage Applications
Mengdi Li, Jiejie Zhu, Lingjie Qin, Yuxi Zhou, Bowen Zhang, Mingchen Zhang, Qiang Su, Ziyue Zhao, Qing Zhu, Huizhong Ma, Huantao Duan, Xiaohua Ma, Yue Hao
Abstract
In this work, high-performance enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) on Si substrate for low-voltage RF applications were demonstrated. The thin-barrier AlGaN (7 nm) and CF<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>4</roman></sub>-based gate recess etching were adopted to realize a positive threshold voltage of 0.13 V. Attributing to the SiN strain layer grown by low-pressure chemical vapor deposition (LPCVD), the sheet resistance of the thin-barrier AlGaN/GaN heterostructure was reduced from 410 to 280 Ω/sq. Hence, the fabricated E-mode thin-barrier AlGaN/GaN HEMTs with regrown ohmic contacts and a small source-drain distance of 850 nm exhibit a high maximum output current of ~1.4 A/mm, a low ON-resistance of 0.5 Ω⋅mm, and a low knee voltage of 1.3 V. Pulsed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> measurement shows that a low current collapse at 20 V drain quiescent condition of 2.1% was achieved. The continuous wave power measurement of the E-mode devices at 3.6 GHz shows a very large peak power added efficiency (PAE) over 65% with drain voltage <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>ds</roman></sub> from 6 to 12 V (peak PAE of 67.21% at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>ds</roman></sub> = 6 V), a high maximum output power density (3.18 W/mm at 12 V), and a linear gain (17.4 dB at 6 V and 21.09 dB at 12 V). These excellent results show that the transistor maintains a constant high PAE and linearly increased gain and output power over the drain voltage variation range, which has great potential and advantages for low-voltage applications.