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Undoped (ND) semi-insulating (SI) liquid encapsulated Czochralski (LEG) GaAs crystals were investigated by photocurrent and temperature-dependent Hall measurements. It is indicated that strong nonuniformities in the distributions of impurities and defects can occur for the NDSILEC GaAs crystal grown under a condition with strong constitutional supercooling. In such case, the deep level that dominates Fermi level is spacial location dependent, and the GaAs crystal becomes a composite consisting of a large number of elementary domains with different conductivities. The sub-bandgap photocurrent response and the carrier transport properties for this kind of composite are quite different from those for homogeneous NDSILEC GaAs.
It is indicated that strong nonuniformities in the distributions of impurities and defects can occur for the NDSILEC GaAs crystal grown. under a condition with strong constitutional supercooling. In such case, the deep level that dominates Fermi level is spacial location dependent, and the GaAs crystal becomes a composite consisting of a large number of elementary domains with different conductivities. The sub-bandgap photocurrent response and the carrier transport properties for this kind of composite are quite different from those for homogeneous NDSILEC GaAs.