Abnormal Degradation of Gate Leakage Current of Schottky-Type p-GaN Gate HEMTs under Repetitive Surge Current Stress

Gate performance of Schottky-type p-GaN HEMTs is susceptible to degradation after electrical stress. The reported degradation is generally monotonic and recoverable. In this work, we observe abnormal degradation behavior of gate leakage current <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(I_{\mathrm{g}\mathrm{s}\mathrm{s}})$</tex>, which is bidirectional and permanent, of device under repetitive surge current stress with high peak values <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(I_{\text{peak}})$</tex>. This may result in a significant increase in power consumption and poor switching characteristics of device. The above degradation phenomenon is confirmed by recovery experiment. We propose that new donor and acceptor traps generated in the p-GaN gate under high electric field and temperature cause the degradation. The generated acceptor traps at the p-GaN/AIGaN interface or in the AIGaN layer may increase the electron barrier height, leading to the decrease of <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</inf><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gss</inf>at low <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$VGS$</tex>. The generated donor traps at metal/p-GaN Schottky junction may enhance the defect-assisted tunneling (DAT), causing the increase of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I_{\mathrm{g}\mathrm{s}\mathrm{s}}$</tex> at high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_GS$</tex>. After stress, part of the electrons and holes, which are captured by the created traps, will not be released, resulting in irreversible degradation. It is confirmed by further stress tests, recovery experiments, temperature-dependent <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I_{\mathrm{g}\mathrm{s}}$</tex>. measurements, and mix-mode TCAD simulation.