An investigation was made of the steady-state Hall mobility and carrier concentration behavior of n-type liquid-encapsulated Czochralski crystals. The measured dependences demonstrated peculiarities, in certain regions, which could not be explained in terms of an homogeneous semiconductor model. It was demonstrated that the observed effects were caused by the complex influence of deep levels in the band-gap and of defect inhomogeneities which were related to the cellular structure of dislocations. The effect of inhomogeneities was intensified under compensation conditions in which Fermi level appeared between the EL2 level and the negative-U double O-related donor level, Ec-0.43eV. The effect of non-uniformities could be modified significantly by changing the excitation conditions. Numerical modelling which was based upon effective medium theory qualitatively confirmed the influence of mesoscopic inhomogeneities, with differing effective activation energies, which were associated with the cellular distribution of the EL2 defect and the O-related donor, EL3. Differing activation energies of the cells and their walls could sometimes cause an intensified effect of inhomogeneities with increasing temperature. The results implied that the appearance of additional scattering which was associated with a change in defect structure should be taken into account.

Influence of defect inhomogeneities on the Hall mobility and concentration in undoped GaAs V.Kažukauskas: Journal of Applied Physics, 1998, 84[4], 2053-61