Structure defects and phase transition in tellurium-doped ZnSe crystals

ZnSe crystals grown from the melt by Bridgman method are characterized by t he presence of such microstructure defects as pores and solid-phase inclusi ons, grain boundaries and packing defects of twinning type. Microstructural and X-ray analysis of the grown crystals has shown that optical non-unifor mity is mainly due to coherent twinned interlayers related to the phase tra nsition wurtzite (W) --> sphalerite (S) on cooling which is incomplete over (0 0 0 1)W parallel to(1 1 1)S planes. The tellurium dopant affects favora bly the optical uniformity and degree of structural perfection of ZnSe(Te) crystals. This is due primarily to the sphalerite structure being completel y stabilized during the growth process and the absence of twinning type pac king defects (PD). Concentration of tellurium is determined which is suffic ient to make complete the W --> S phase transition. (C) 1999 Elsevier Scien ce B.V. All rights reserved.