Ar+-irradiation-induced damage in hydride vapor-phase epitaxy GaN films

The authors have investigated the electrical characteristics of hydride vapor-phase epitaxy GaN films exposed to Ar+ irradiation, employing Schottky barrier diodes. The Ar+ irradiation tends to largely increase the effective carrier concentration in the near surface region of GaN up to ∼25 nm, due to the generation of donor-type N vacancy defects, compared to the original value before the irradiation. More interestingly, acceptor-type deep-level defects are found to be formed at ∼2.1, ∼2.9, and ∼3.2 eV below the conduction band in the subsequently deeper region, in which Ga vacancies introduced by the Ar+ irradiation are considered to be in-diffused and immediately combined with hydrogen. These N vacancies and hydrogenated Ga vacancies formed are dominantly responsible for changing the depth profiles of the effective carrier concentration via the carrier generation, the carrier trapping, and/or carrier compensation.