Defect depth profiling of CdZnTe using high-energy diffraction measurements

We utilized monochromatic high energy synchrotron x-rays (100 keV) to perform transmission diffraction measurements on bulk cadmium zinc telluride (Cd_1-xZn_xTe, x to approximately 0.1) crystals used for room temperature radiation detectors. The high-energy measurements assess the crystalline properties throughout the thickness (2-3 mm) of the structures and we determined - in combination with standard high-resolution diffraction measurements - that most defects propagate through the width of the sample. Maps of both composition and crystalline quality were generated using both the high energy and standard diffraction sources and a clear correlation was observed for both composition variation and for mosaic structure. In some cases, up to twenty individual peaks are observed in a rocking curve with a beam size of 100×100 μm² which allows for a determination of the crystallite size. This experiment represents the first time in which transmission high-energy x-ray diffraction techniques have been applied to examine the crystal quality of Cd_1-xZn_xTe used in nuclear radiation detector applications. The technique allows one to measure the bulk structural properties of thick (mm's) crystals and the technique is particularly useful because these crystals are used as bulk devices. Hence, this enables one to perform a proper analysis of the relationship between the structural defects (present in the bulk) and the detector performance.