The liquid encapsulated, vertical Bridgman growth process has been carried out for the growth of 3 inch diameter GaAs single crystals. Molten GaAs in a pyrolytic boron nitride curcible is gradually crystallized from seeded bottom to top of the melt by means of pulling down the crucible. In this method, B 2O 3 is used as an encapsulant to suppress decomposition and evaporation of the arsenic from the molten and crystalline GaAs. It was found that B 2O 3 prevents GaAs from directly contracting the crucible wall, thus suppressing grain boundary nucleations and enabling reproducible growth of the single crystals. The 3 inch diameter crystals grown by this method have dislocation densities of the 1 5 to 1 2 level of those grown by the standard LEC method. They are of high purity, undoped semi-insulating, and are suitable for integrated circuit substrates.