Probing the effect of point defects on the leakage blocking capability of Al_(0.1)Ga_(0.9)N/Si structures using a monoenergetic positron beam

摘要

Vacancy-type defects in Al_(0.1)Ga_(0.9)N were probed using a monoenergetic positron beam. Al_(0.1)Ga_(0.9)N layers with different carbon doping concentrations ([C]=5 × 10~(17)-8 × 10~(19) cm~(-3)) were grown on Si substrates by metalorganic vapor phase epitaxy. The major defect species in Al_(0.1)Ga_(0.9)N was determined to be a cation vacancy (or cation vacancies) coupled with nitrogen vacancies and/or with carbon atoms at nitrogen sites (C_Ns). The charge state of the vacancies was positive because of the electron transfer from the defects to C_N-related acceptors. The defect charge state was changed from positive to neutral when the sample was illuminated with photon energy above 1.8 eV, and this energy range agreed with the yellow and blue luminescence. For the sample with high [C], the charge transition of the vacancies under illumination was found to be suppressed, which was attributed to the trapping of emitted electrons by C_N-related acceptors. With increasing [C], the breakdown voltage under the reverse bias condition increased. This was explained by the trapping of the injected electrons by the positively charged vacancies and C_N-related acceptors.