Semi-Insulated ${\rm Cd}_{1-{\rm x}}{\rm Zn}_{\rm x}{\rm Te}$ Grown by the Vertical Gradient Freeze Method

One of the most fundamental parameters relating to bulk crystal growth of CZT from the melt is the temperature gradient applied at the solid-liquid interface throughout the growth cycle.
${\rm Cd}_{1-{\rm x}}{\rm Zn}_{\rm x}{\rm Te}$
ingots grown by the vertical gradient freeze method, using dynamic temperature gradients are presented. Several complementary experimental methods have been implemented to investigate the material including mapping of resistivity, photosensitivity, infrared transmission, and measuring the low-temperature photoluminescence. Photoconductivity mapping was performed by the contactless method. Correlation of contactless resistivity and photoconductivity maps illustrate that both parameters are anticorrelated in the middle of the ingots, but correlated towards the tail end of the ingot. This observation is explained in terms of an energy shift of the Fermi level that changes the average occupation of a mid-gap level. This reasoning is further supported by photoluminescence data.