Reassessment of ionized impurity scattering and compensation in GaAs and InP including correlation scattering

The pressure dependence of the electron Hall mobility has been measured in a wide variety of InP and GaAs samples. The results, analyzed by a number of techniques, indicate that, in general, very good agreement can be obtained between theory and experiment for pure material at temperatures where ionized impurity scattering is unimportant. When heavily doped samples of liquid-phase epitaxy (LPE) GaAs and vapor-phase epitaxy (VPE) InP were measured it was not possible to predict the experimental pressure dependence of the mobility using the Brooks-Herring theory of scattering from ionized impurities. The possibility of inaccuracies in analysis have been reduced by using an iterative solution of the Boltzmann equation, phase shift calculations, and also Moore's analysis [Phys. Rev. 160, 618 (1967)] for dressing and multi-ion corrections. However, these proved to be inadequate and we obtain the best agreement with experiment using the theory of Yanchev et al. [J. Phys. C 12, L765 (1979)] for scattering from a correlated distribution of impurities. The important effects of impurity correlation have been substantiated by studying samples of GaAs grown by molecular-beam epitaxy (MBE) and bulk GaAs subjected to neutron transmutation doping. The inability of impurities to correlate in such material is demonstrated by the close agreement between Brooks-Herring theory and experiment for these samples. When correlation scattering is taken into account, it becomes possible to explain the observed mobilities in heavily doped materials without having to always postulate autocompensation, as has been done by other authors.