Positron Annihilation Spectroscopy on Nitride-Based Semiconductors

Abstract

Positron annihilation is a nondestructive tool for investigating vacancy-type defects in materials. Detectable defects are monovacancies to vacancy clusters, and there is no restriction of sample temperature or conductivity. Using this technique, we studied native defects in (AlInGa)N grown by metalorganic vapor phase epitaxy and plasma-assisted molecular beam epitaxy. For InxGa1-xN, the defect concentration increased with increasing In composition x and reached a maximum at x = 0.44–0.56. The major defect species was identified as cation vacancies coupled with multiple nitrogen vacancies. For AlxGa1-xN, the vacancy-type defects started to be introduced at above x = 0.54 and their concentration increased with increasing x. The observed behavior of point defects was discussed in terms of the transition of the growth mode.