INTERNAL-FRICTION AND SYMMETRY OF INTRINSIC POINT-DEFECTS IN GAAS

To study the structure and symmetry of intrinsic point defects in GaAs, internal-friction measurements on n-type single crystals of different doping levels were performed in the range 80-440 K for a frequency of about 105 kHz. Actually, we detected damping peaks due to relaxation of point defects which are shown to be of <110> orthorhombic symmetry. The present analysis of the peak spectra supports an explanation in terms of midgap defect reorientations where charge-state effects seem to play a central role. The determination of the kinetic parameters of the relaxations yields activation energies of 0.6-0.8 eV for the nu-13 and 0.85-1 eV for the nu-12 reorientation. Remarkably large tau-0(-1) values of 10(18) sec-1 are found for the latter. They are attributed to activation entropies of the order 10k.