Abstract: Gallium is zone refined in a stationary, vertical, double annulus refiner. Impure gallium is contained between walls of a first annulus that are made of a material that does not impart impurities to the gallium. At least one of the walls is made of a flexible material. A cooling fluid is circulated through a second annulus enveloping the first annulus. The gallium is zone refined by moving through the gallium ingot one or more molten zones formed by radio frequency waves from at least one reciprocating radio frequency heating induction coil. After the necessary number of passes, the ingot is cropped without introducing contaminants and refined gallium with purities between 79 and 89 is recovered. LEC single crystal GaAs made with the so refined gallium has very uniform electrical characteristics.

Abstract: Cd and Te are purified by multiple-pass zone refining in the presence of a small amount of an added gettering substance chosen from Cd, Te and CdTe. In the purification of Cd, Te, or CdTe is added, the amount of Te or of Te in CdTe being less than the amount of Te in the Cd-rich eutectic composition between Cd and Te. In the purification of Te, Cd or CdTe is added, the amount of Cd or of Cd in CdTe being less than the amount of Cd in the Te-rich eutectic composition between Cd and Te. The Cd and Te so purified have an improved purity as witnessed by SSMS analyses, the increased ductility of the Cd and a much higher yield of the number of slices of CdHgTe produced with the refined Cd and Te meeting the specifications for carrier concentration and mobility.

Abstract: Gallium arsenide single crystals are grown under an encapsulant of boron oxide which contains a predetermined amount of water in the range of 200 to 1000 ppm. The GaAs crystals so produced are stable in that the resistivity of the GaAs upon heat treatment remains substantially constant. The GaAs single crystals as produced may be subjected to a bulk anneal to further improve the stability.

Abstract: Aluminum arsenide crystals, wherein gallium has been substituted for a minor portion of aluminum and which may be represented by the general formula Al.sub.1-x Ga.sub.x As wherein x has values in the range of 0.02 to 0.30, are annealed at a temperature of at least 700.degree. C in presence of arsenic vapor whereby the stability of the crystals against attack by moisture is improved.