IDENTIFICATION OF VACANCIES BY THE CORE ELECTRON MOMENTUM DISTRIBUTION - APPLICATION TO INP BASED COMPOUND SEMICONDUCTORS

We show that the Doppler broadening measurement of positron annihilati on radiation can be used to identify vacancies in semiconductors. Anni hilation of the trapped positron with surrounding core electrons revea ls chemical information that becomes visible when the experimental bac kground is reduced by the coincidence technique. The utility of the me thod is demonstrated by several examples, especially in InP based comp ounds. In electron irradiated InP we show that the sublattice of the v acancy can be identified by the magnitude of the core annihilation spe ctrum. The atomic structure of the DX center is studied in AlxGa0.51-x In0.49P (x = 0.36) overlayers. Due to the low magnitude of the measure d core annihilation spectrum, we infer that the DX center consists of a vacancy in the group-III sublattice. As an example of a vacancy-impu rity pair, we demonstrate that the native vacancy defects in heavily Z n-doped InP can be identified as P vacancies decorated by Zn atoms.