The results of growth of semi-insulating GaAs crystals with diameters of 100-150 mm and lengths up to 200 mm from the melt with starting charges up to 25 kg by the low-temperature gradient Vapour Pressure Controlled Czochralski method (VCz) are given and compared with the state of art of LEC growth. The methodical process optimization was assisted by global numerical simulations. A slightly convex interface morphology has been found to be the most suitable for moderate EPD of ~104 cm-2 in 150-mm crystals whilst simultaneously depressing the probability of dislocation bunchings. The carbon concentration was controlled down to values below 1014 cm-3. Electrical properties, including the EL2° content, are discussed. The first results of GaAs VCz crystals grown without B2O3 encapsulant are given. A reduced boron concentration but enhanced carbon and vacancy concentrations have been observed.

Keywords: GaAs, VCz, Dislocation density, Electrical properties