Nonequilibrium acoustic phonons in ZnTe at liquid-helium temperatures: Effect of impurities and structural defects on the phonon mean free path

ZnTe crystallites isolated from a druse of coarse-grained polycrystalline ZnTe, prepared by chemical vapor synthesis at a temperature of ～650°C, were studied using x-ray diffractometry, luminescence, and the heat pulse technique. The crystallites are stacked in {110}-oriented macroscopic layers with a common twin system. The {111} twin planes separated at a distance of 50–100 μm are perpendicular to the (110) growth layers. Acoustic phonon propagation was studied using the heat pulse technique. A comparison of the responses to the arrival of differently polarized phonons in a given sample with the responses obtained on high-purity coarse-grained ZnTe with randomly distributed twin systems with a separation of 5–10 μm and on twin-free single-crystal ZnTe suggests that twins radically affect the scattering of acoustic phonons. The mean free paths of LA, FTA, and STA phonons were determined by comparing the experimental responses with Monte Carlo calculations.