Point defects in GaP single crystals investigated by mechanical damping

The dependence of mechanical damping of LEC (liquid encapsulated Czochralski) crystals of GaP: S was measured in the temperature range 300… 600 K and at frequencies near 70 and 140 kHz, respectively. In samples of different stoichiometry two peaks could be observed: Peak A at 350 K and peak B at 450 K. Peak A is attributed to the relaxation of point defects near the surface, peak B is probably due to Ga vacancies.