Drain current (ID) collapse-free i-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs) with and without surface passivation (electron-beam evaporated SiO2) were demonstrated using dc and pulsed (120 Hz) IDs-VDS characteristics up to the drain supply voltage of 40V. The observation of small ID transients and negligibly small hysteresis widths with small white light illumination effects on both passivated and unpassivated i-GaN/AlGaN/GaN HEMTs confirms the suppression of collapse related traps. Three and two thermally activated trap levels were observed in passivated (+0.395, -0.079, and -0.949 eV) and unpassivated (-0.066 and -0.368 eV) AlGaN/GaN HEMTs, respectively. However, I-GaN/AlGaN/GaN HEMTs with and without surface passivation exhibited only one trap level at -0.161 eV. These results show that the addition of thin cap layer i-GaN screens the collapse-related surface states/traps from channel.
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