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Control of Threshold Voltage of AlGaN/GaN HEMTs by Fluoride-Based Plasma Treatment: From Depletion Mode to Enhancement Mode

2006; Institute of Electrical and Electronics Engineers; Volume: 53; Issue: 9 Linguagem: Inglês

10.1109/ted.2006.881054

1557-9646

Yong Cai, Yugang Zhou, Kei May Lau, Kevin J. Chen,

ZnO doping and properties

This paper presents a method with an accurate control of threshold voltages (V th ) of AlGaN/GaN high-electron mobility transistors (HEMTs) using a fluoride-based plasma treatment. Using this method, the V th of AlGaN/GaN HEMTs can be continuously shifted from -4 V in a conventional depletion-mode (D-mode) AlGaN/GaN HEMT to 0.9 V in an enhancement-mode AlGaN/GaN HEMT. It was found that the plasma-induced damages result in a mobility degradation of two-dimensional electron gas. The damages can be repaired and the mobility can be recovered by a post-gate annealing step at 400 degC. At the same time, the shift in V th shows a good thermal stability and is not affected by the post-gate annealing. The enhancement-mode HEMTs show a performance (transconductance, cutoff frequencies) comparable to the D-mode HEMTs. Experimental results confirm that the threshold-voltage shift originates from the incorporation of F ions in the AlGaN barrier. In addition, the fluoride-based plasma treatment was also found to be effective in lowering the gate-leakage current, in both forward and reverse bias regions. A physical model of the threshold voltage is proposed to explain the effects of the fluoride-based plasma treatment on AlGaN/GaN HEMTs