Probing the effect of point defects on the leakage blocking capability of Al0.1Ga0.9N/Si structures using a monoenergetic positron beam

• Published in: Journal of applied physics 2016-12, Vol.120 (21)
• Main Authors: Uedono, Akira, Zhao, Ming, Simoen, Eddy
• Format: Article
• Language: English
• Subjects: Applied physics; Carbon; Cations; Electron transfer; Electrons; Epitaxial growth; Metalorganic chemical vapor deposition; Point defects; Positron beams; Silicon substrates; Trapping; Vacancies
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4970984

Vacancy-type defects in Al0.1Ga0.9N were probed using a monoenergetic positron beam. Al0.1Ga0.9N layers with different carbon doping concentrations ([C] = 5 × 1017−8 × 1019 cm−3) were grown on Si substrates by metalorganic vapor phase epitaxy. The major defect species in Al0.1Ga0.9N was determined to be a cation vacancy (or cation vacancies) coupled with nitrogen vacancies and/or with carbon atoms at nitrogen sites (CNs). The charge state of the vacancies was positive because of the electron transfer from the defects to CN-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 CN-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 CN-related acceptors.