EFFECTS OF TOTAL LIQUID ENCAPSULATION ON THE CHARACTERISTICS OF GAAS SINGLE-CRYSTALS GROWN BY THE VERTICAL GRADIENT FREEZE TECHNIQUE

Total liquid encapsulation with B2O3 has been used to grow 50 mm diameter GaAs single crystals in PBN crucibles in a vertical gradient freeze configuration. The B2O3 layer efficiently prevents direct contact between the crucible and the GaAs charge and reproducible growth of single crystals can be achieved. The effect of B2O3 water content on the structural and electrical characteristics of the crystals was investigated. Water vapor can be trapped between the crystal and the crucible affecting the surface morphology of the crystals. The water content of the B2O3 encapsulant was found to affect the electrical properties of the crystals in a manner similar to what is observed for growth of GaAs crystals by the liquid encapsulated czochralski technique. Crystals grown encapsulated with dry B2O3 have been ion-implanted with silicon. The implant activations are comparable to those obtained on LEC grown crystals. Total liquid encapsulation in vertical gradient freeze can be used to produce device quality substrates.