POSITRON BEAM ANALYSIS OF SEMICONDUCTOR-MATERIALS USING A 2-DETECTOR DOPPLER BROADENING COINCIDENCE SYSTEM

Doppler-broadening measurements can be improved by using a second Ge-d etector for the coincidence detection of the second annihilation photo n. The coincidence condition in combination with an energy relation re sults in a reduction of the background by a factor of 100 compared to a single detector system. This background reduction opens up the possi bility of performing accurate measurements of the high momentum part o f Doppler-broadened annihilation spectra. We have used this technique for the analysis of a metal oxide semiconductor system and electron-ir radiated. As- and Sb-doped silicon.