К ВОЗМОЖНОСТИ ВЫРАЩИВАНИЯ ОБЪЕМНЫХ КРИСТАЛЛОВ Si—Ge МЕТОДОМ ОСЕВОГО ТЕПЛОВОГО ПОТОКА ВБЛИЗИ ФРОНТА КРИСТАЛЛИЗАЦИИ

A technique for crucibleless growth of single−crystal silicon and its alloys with germanium is developed. For this purpose, the setup of floating zone method was used, which was equipped with additional so−called AHP heater. The heater forms around itself a melt zone that is suspended between the growing crystal, the feeding rod and correspondingly the bottom and the top surfaces of the AHP heater by forces of surface tension. To protect the graphite casing of the heater against the aggressive action of molten silicon, the casing surface was coated with SiC having a special nano−crystalline structure. The system of automation control of the AHP crystallization mode is described. It allows controlling the thermal field near the growing crystal with an accuracy of about 0.05−0.1 K. Numerical computations of heat and mass transfer during the solidification of SixGe1−x alloy with a 2% Si content, as well as shaping of the free Si−Ge melt surface during the crystal pulling were performed. Uniform bulk crystals were obtained. The range of the highest melt layer at which the shaping process remains stable was found to be 10−20 mm. The grown As−doped Si single crystals showed to have strong twining directly caused by presence of the SiC inclusions revealed in the crystal bulk. The possibility to achieve a convex and nearly flat shape of the interface by means of the AHP heater was proved. The layered mechanism of Si crystallization was found to be present during crystal growth on a seed in the [111] direction, with the faceted area under certain conditions occupying almost the entire crystal cross section