Threshold Voltage Hysteresis and Gate Leakage in AlGaN/GaN HEMTs

Temperature-dependent threshold voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {TH}}$ </tex-math></inline-formula>) hysteresis and gate leakage current are characterized in commercial AlGaN/GaN high electron mobility transistors (HEMTs). Significant peaks in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {TH}}$ </tex-math></inline-formula> hysteresis are observed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$220 \; \pm \; 10$ </tex-math></inline-formula> K. Gate leakage current increases with increasing temperature for as-processed devices and devices irradiated with 1.8-MeV protons at <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-state bias, due to Mott hopping. In contrast, gate leakage current for devices irradiated or stressed at <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-bias increases strongly with decreasing temperature below 200 K. The increased gate leakage at low temperatures and large negative bias in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-bias stressed and/or irradiated devices is attributed primarily to trap-assisted tunneling through oxygen impurities (ON) in AlGaN. Dehydrogenation of ON-H impurity centers during stress and/or <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-bias irradiation evidently plays a key role in enhanced cryogenic gate leakage at large negative bias in these devices.