Fabrication of AlGaN/GaN HEMT using TMAH pre-treatment and analysis of electrical characteristics by proton irradiation

In this study, we analyzed the effects of proton irradiation and surface pre-treatment on gallium nitride (GaN)-based high electron mobility transistors (HEMTs) and evaluated their reliability against proton irradiation. The variation in DC performance of the AlGaN/GaN HEMT was analyzed by irradiating a proton energy of 15 MeV at proton fluence of 5 × 10¹³ cm⁻². During the pre-treatment process, the active region and mesa isolation region (Sample 1) and mesa isolation region (Sample 2) were treated with trimethylammonium (TMAH) solution, respectively. And the variation in transfer characteristics of before and after proton irradiation were compared. In terms of transfer characteristics of before and after proton irradiation, the drain current decreased after proton irradiation due to increase the sheet resistance and contact resistance. Also, acceptor-like and donor-like vacancies were generated on the AlGaN/GaN surface due to proton irradiation, inducing the displacement damage effect. In particular, the variation in on current (I_on) increased by 7.26 percentage point (%p) when TMAH treatment in the Sample 2 compared to when TMAH treatment in the Sample 1 after proton irradiation. The damage caused by dry etching and plasma-enhanced chemical vapor deposition (PECVD) plasma enhanced the proton irradiation effect because the AlGaN/GaN surface was not completely treated by the TMAH solution due to SiN deposition. These results demonstrate that the radiation hardness of GaN-based HEMTs is affected by the AlGaN/GaN surface quality and pre-treatment using TMAH solution is necessary to increase the resistance to proton irradiation.