The growth and comparison of large-diameter vertical Bridgman CdZnTe and CdTe

Abstract

There is currently a need for high yields of large-area CdTe and C d - x Z n x T e substrates for the growth of infrared (IR) detector material. We have recently grown high-quality, 64 mm diameter, vertical Bridgman C d 1− x Z n x T e ( x = 0.04) and CdTe under virtually identical conditions, with an axial thermal gradient of 55°C cm -1 at the ampoule wall, a solidification velocity of 1.0 mm h -1, and a post-solidification cooling rate of 10°C h -1. The growth program was designed to minimize excess stress in the crystals. We have obtained large-area (111)-oriented wafers from each double. We explore the defect structure of these wafers using X-ray rocking curve (XRC) mapping, whole-wafer X-ray synchrotron white beam topography, chemical etch pit analysis, and optical and infrared microscopy. We also utilize Fourier transform infrared (FTIR) transmission mapping to explore the chemical and the optical properties of the materials. We have correlated the structural, chemical, and optical properties with the effects of substituting Zn into CdTe and the corresponding physical and mechanical properties of the ternary CdZnTe. In particular, CdZnTe exhibits a decrease in crystalline defects and an improvement in morphological uniformity, increasing its suitability for use as IR detector substrate material.