Low-angle boundaries in ZnGeP2 single crystals

The structure of low-angle boundaries in ZnGeP2 crystals grown by the vertical Bridgman technique was studied using Borrmann X-ray topography. The slip systems of the dislocations in the boundaries were identified by studying the contrast rosettes generated by the Borrmann effect, in the region near the dislocation core. It was shown that the boundaries are of two types: type I consists of edge dislocations of the {10}110 slip system, and type II of edge and mixed dislocations of the {010}100 slip system. The boundaries of both types, consisting of pure edge dislocations with lines along [001], are symmetrical tilt boundaries with [001] rotation axes. The misorientations generated by the boundaries were estimated to range between 2-20 and 1-40, respectively. Low-angle boundaries are thought to be formed by polygonization of dislocations, caused by thermoelastic stresses.