Effect of random potential fluctuations on electron transport inn-type InSb

A number of previous investigators have concluded that the low-temperature transport properties of n-type InSb can only be understood by assuming the existence of an impurity band which is separated from the conduction band by a finite binding energy. However, we show that the experimental results are fully consistent with a one-band interpretation as long as the effects of potential fluctuations due to random inhomogeneities in the impurity concentration are considered. Single-site electron mobilities are compared with a large body of experimental data from the literature covering the temperature range 1.3 to 80 K. Experiment and theory are found to agree well as long as the magnitude of the fluctuations {γ} is small compared to the thermal energy of the electrons E₀. However, when {γ}{}E₀ in compensated samples at low temperatures, the experimental mobilities fall far below the results of the single-site theory (which ignores the fluctuations). This behavior is consistent with that observed for one-band conduction in other semiconductors. Also considered are effects of the potential fluctuations in the alternative case where an impurity band is assumed to be present.