Growth striations and dislocations in highly doped semiconductor single crystals

Microsegregation and structural inhomogeneities in highly doped GaSb(Si) and InAs(Ga) single crystals grown under various heat and mass transfer conditions were analyzed using X-ray topography, high-resolution X-ray diffractometry, digital image processing and spectral analysis of signals. It was shown that a decrease in the convective flow intensity during crystal growth by the vertical Bridgman method with axisymmetric upper heat supply eliminates microsegregation growth striations and improves homogeneity of crystals on a micro-scale in comparison with the Czochralski method. Some specific features in X-ray topography images of growth striations caused by a high silicon concentration and dopant state deviation from an ideal substation solid solution were revealed in GaSb(Si). It is established that elastic stresses arising at large compositional variations in growth striations can relax by means of misfit dislocations formation. The magnitude of compositional fluctuations in InAs(Ga) was quantitatively estimated using conditions of misfit dislocation formation in such layered-inhomogeneous crystals.