  This article presents studies on low-field electrical conduction in the range
4-to-300 K for a ultrafast material: InGaAs:ErAs grown by molecular beam
epitaxy. The unique properties include nano-scale ErAs crystallines in host
semiconductor, a deep Fermi level, and picosecond ultrafast photocarrier
recombination. As the temperature drops, the conduction mechanisms are in the
sequence of thermal activation, nearest-neighbor hopping, variable-range
hopping, and Anderson localization. In the low-temperature limit,
finite-conductivity metallic behavior, not insulating, was observed. This
unusual conduction behavior is explained with the Abrahams scaling theory.
