Trapping effect evaluation of gateless AlGaN/GaN heterojunction field-effect transistors using transmission-line-model method

An electric-field-dependent trapping effect was observed in our AlGaN/GaN transmission-line-model (TLM) structure. Therefore, we adopted a “gradual voltage stress” scheme to induce a similar trapping effect, that is, a similar sheet resistance variation (ΔRSH) for all intervals of our AlGaN/GaN TLM structure. By measuring the TLM structure under “gradual voltage stress” (stressed TLM measurement), we investigated the trapping effects in gateless AlGaN/GaN heterojunction field-effect transistors. 10 nm of Al2O3 passivation film substantially decreased the voltage-stress-induced ΔRSH, suggesting surface traps were involved. The feasibility and reproducibility of the stressed TLM measurement method was confirmed with repeated passivation.