VERTICAL BRIDGMAN GROWTH AND CHARACTERIZATION OF LARGE-DIAMETER SINGLE-CRYSTAL CDTE

We report on the growth of 64 mm diameter single crystals of CdTe using a large-bore, high-thermal mass, multizone vertical Bridgman furnace. Ampoules are carefully prepared so that the probability of melt adhesion or spurious nucleation is reduced. The longitudinal thermal gradient imposed on the solidifying boule is less than 10-degrees-C cm-1, and the hot and cold zone temperatures have been adjusted to reduce the interface curvature and the thermal stress on the growing crystal and the solidified portion of the boule. Post-solidification processing of the boule, including in-situ annealing and cooling rate, is designed to reduce the size of precipitates as well as residual strain. Wafers taken from the crystals have been structurally and chemically characterized. We have been able to establish a correlation between features identified on high-quality surfaces of CdTe using synchrotron white beam topography (SWBT) and Nakagawa-etch-pit micrographs. We propose that SWBT can be utilized as an alternative to destructive etch pit analysis to characterize the {111}A surface defect structure, as well as to image the Nakagawa-inert {111}B surface or other surfaces of interest.