Migration of Te inclusions in CdZnTe single crystals under the temperature gradient annealing

The migration of Te inclusions in CdZnTe single crystals has been investigated under temperature gradient fields in saturated Cd/Zn vapor. The migration velocity of Te inclusion upwards temperature gradient is calculated in consideration of the ordinary and thermal diffusion during annealing. The critical annealing conditions for eliminating Te inclusions are supposed based on the calculations. However, the necessary annealing conditions (annealing temperature and time) are always much larger than the suggested ones. The obtained annealing results can be summarized into three categories based on the elimination efficiency η of Te inclusions. Excluding the influence of insufficient annealing conditions, η always tends to be larger than 70% but with a restricted average value around 85%. Further discussions indicate that the interface kinetics, such as the size and void effects, have great influence on η and the migration behaviors of Te inclusions. The size effect likely results in longer annealing time, while the void effect leads to the density of Te inclusions (or voids) with diameter of 5-25 μm increase after long-time annealing.