Amplitude dependent damping in HgI 2 wide band gap semiconductor

Abstract

Amplitude dependent damping in crystals is considered as one of the methods of mechanical spectroscopy for investigating different mechanisms of dislocation microplasticity. A short review of the amplitude dependent damping studies in semiconductors is presented. A new acousto–optic experimental technique for studying a dislocation point defect interaction developed over the last several years is described. Experimental data of photoacoustic investigations of HgI 2 single crystals obtained in a wide amplitude range at frequencies of longitudinal vibrations of about 100 kHz are reviewed. More recent results are presented as well. Besides, acousto–electric and acousto–optic (for a band of photoluminescence spectrum) effects which result from a high amplitude ultrasonic treatment (HAUT) with the amplitudes from the amplitude dependent damping range illustrate the possibilities of the technique. A model of an electron or hole trapping center which transforms in a dislocation pinning point during the sample illumination is assumed to be the most convenient to explain the experimental data. Under the influence of HAUT, one can destroy (due to dislocation depinning) the center which consists of the dislocation, point defect (it is, surely, a lattice, iodine or mercury, vacancy or interstitial) and the trapped electron or hole. A binding energy between the dislocation and the photosensitive pinning point defect has been estimated by displacement under the HAUT of specific points in the luminescence excitation spectrum. A possible practical use of HAUT for a restoration of performance of γ-ray HgI 2 detectors is briefly discussed.