https://doi.org/10.15407/jopt.2018.53.199

Optoelectron. Semicond. Tech. 53, 199-212 (2018)

Ya.M. Olikh, M.D. Tymochko, M.I. Ilashchuk1

RELAXATION FACTORS OF ACOUSTIC CONDUCTIVITY IN CdTe

The acoustic conductivity kinetics was studied to find out mechanisms of acoustic conductivity relaxation σUS(t) in n-type low-ohmic CdTe single crystals (NCl≈1024 m–3) in the temperature range (77…300) К, when ultrasound is turned-on and turned-off. The separate comparison of the single amplitudes stages temperature dependences σUS(t) with the corresponding temperature changes of concentration and mobility, obtained from independent Hall measurements, allowed us to relate the concentration effects with "instantaneous" changes, and mobility – with "long-term" acoustically induced changes σUS(t). The comparison of growth with temperature of velocities inherent to separate mobility components with changes in the σUS(t) amplitudes for respective stages allowed us to part the time frames for exhibition of various mechanisms. Thus, the two scattering components related to "dislocations" and "neutral impurities" and characterized by low velocities of temperature changes, which are close to the speed of the instantaneous component changes, were attributed to the factors that define the instantaneous acoustic-induced changes σUS(t). The scattering component ascribed to "ionized impurities", as the fastest one, is characterized by the largest acoustic-induced growth increase σUS(t) and attributed to factors that determine long-term changes in σUS(t). Possible mechanisms of acoustic-stimulated point-defect complexes structure rebuilding processes in the near dislocation crystal regions have been discussed. In particular, it has been noted that there is a diffusion drag of point defects from the volume of the crystal (sub-block) into the potential wells of near-dislocation clusters by the dynamic acoustically-induced oscillations of dislocations with the amplitude that significantly exceeds the lattice parameter. This process can lead to capturing a significant number of point defects (including the charged ones) into the dislocation traps, which results in the decrease of ionized centers concentration. Keywords: ultrasound, CdTe crystals, point defects, dislocation clusters, Hall effect, scattering mechanisms.