Positron beam analysis of semiconductor materials using a two-detector Doppler broadening coincidence system

Doppler-broadening measurements can be improved by using a second Ge-detector for the coincidence detection of the second annihilation photon. The coincidence condition in combination with an energy relation results in a reduction of the background by a factor of 100 compared to a single detector system. This background reduction opens up the possibility of performing accurate measurements of the high momentum part of Doppler-broadened annihilation spectra. We have used this technique for the analysis of a metal oxide semiconductor system and electron-irradiated, As- and Sb-doped silicon.