Oxygen annealing impact on β-Ga2O3 MOSFETs: Improved pinch-off characteristic and output power density

• Published in: Applied physics letters 2020-09, Vol.117 (13)
• Main Authors: Lv, Yuanjie, Liu, Hongyu, Wang, Yuangang, Fu, Xingchang, Ma, Chunlei, Song, Xubo, Zhou, Xingye, Zhang, Yanni, Dong, Pengfei, Du, Hanghai, Liang, Shixiong, Han, Tingting, Zhang, Jincheng, Feng, Zhihong, Zhou, Hong, Cai, Shujun, Hao, Yue
• Format: Article
• Language: English
• Subjects: Annealing; Applied physics; Buffer layers; Continuous radiation; Depletion; Direct current; Field effect transistors; Gallium oxides; MOSFETs; Radio frequency; Radio signals; Semiconductor devices; Transconductance
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0021242

In this Letter, we present direct current (DC), small signal radio frequency (RF), and large signals with pulsed and continuous wave (CW) studies and characterization on oxygen annealed (OA) β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) with significantly improved CW output power density (Pout) when compared to other β-Ga2O3 RF devices. The OA process is found to be useful in compensating and neutralizing the donors in the unintentionally doped (UID) buffer layer and, hence, suppressing a second depletion effect in this UID layer. The device demonstrates a peak DC drain current of 200 mA/mm, a transconductance of 11 mS/mm, and an on/off ratio of 109. Small-signal RF characterization indicates a cut-off frequency and maximum oscillation frequency (fT/fmax) of 1.8 GHz and 4.2 GHz, respectively. The device also shows an output power (Pout)/peak power added efficiency (PAE)/gain of 0.4 W/mm/10%/3.2 dB and 0.43 W/mm/12%/3.6 dB for CW and pulsed signals, respectively, at an operation frequency of 1 GHz.