Abstract: A process that, without doping of PBN crucibles, produces semi-insulating GaAs having low, or essentially no, dislocation density; and in which the crystal may be in situ annealed after growth. The process is a variant of the Heat Exchanger Method (HEM) disclosed in U.S. Pat. No. 3,898,051. Crack-free, semi-insulating GaAs crystals having low dislocation density are grown from presynthesized undoped GaAs meltstock in sealed quartz (vitreous silica) crucibles, without the need for an encapsulant. One aspect of the invention features seeded growth of <100> orientation crystals having a dislocation density 1-2 orders of magnitude less than that of the seed; in another aspect, crystals having fewer than 500 dislocations/cam.sup.2 in their center column are grown without a seed.

Abstract: A novel apparatus is disclosed for controlling the temperature of the top surface of the capillary die and the adjacent meniscus during growth of a crystalline body. The apparatus includes a tiltable heat shield located so that by appropriately positioning it about its tilt axis it is possible to adjust the temperature distribution about the top end of the capillary die. This temperature control assists in ensuring that a crystalline body grown by means of the capillary die process will have a substantially constant cross-sectional size.