Characterisation of deep electron states in LEC grown GaAs material

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Abstract
Deep electron states in undoped GaAs grown by the liquid-encapsulated Czochralski (LEC) method using a pyrolitic boron nitride (PBN) crucible were investigated by DLTS and Hall measurements. Six electron traps with activation energies ranging from 0.14 to 0.82 eV were detected. One of these traps, with an energy of 0.27 eV (EL6), was reduced in concentrations by more than an order of magnitude by an 800 degrees C heat treatment for 1 h. Temperature-dependent Hall measurement on as-grown material indicated that the 0.27 eV state plays an important role in the decrease of the resistivity of undoped crystals that have a low concentration of carbon impurity. The effect of gamma irradiation on the annealing properties of the traps was also demonstrated.