(Invited) Point Defect Characterization of Group-III Nitrides by Using Monoenergetic Positron Beams

Abstract

Positron annihilation is a powerful technique for evaluating point defects in semiconductors. Using this technique, one can detect vacancy-type defects in subsurface regions with high-sensitivity. We have used monoenergetic positron beams to probe native vacancies in InGaN grown on sapphire and GaN substrates by metalorganic vapor phase epitaxy. It was found that vacancy-type defects were introduced with increasing InN composition, and the major defect species was identified as complexes between a cation vacancy and a nitrogen vacancy. The concentration of the defects was found to be suppressed by Mg doping, suggesting that Mg is an excellent suppressor of cation vacancies in InGaN. The crystal quality of the InGaN films was greatly improved using the GaN substrate, but point defects, especially vacancy-type defects were found to present in the film.