Mobility of Electrons in Compensated Semiconductors. I. Experiment

Abstract

Ionized-impurity scattering mobilities were obtained from Hall-mobility measurements for a series of n-type germanium samples between 10 and 40°K. The specimens were prepared by transmutation doping, and contain a constant concentration of minority impurities ($N_{\mathrm{Ga}}=2.9\mathrm{}\times {10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$), while the compensation ratio $K=\frac{N_{\mathrm{minor}}}{N_{\mathrm{major}}}$ varies from 0.27 to 0.95. At the low temperatures considered, the number of electrons in the conduction band is very small, and the number of ionized impurities is essentially the same in all samples, $N_I\cong 2N_{\mathrm{Ga}}$. Under these conditions, the screening of scattering centers is due to ionized impurities rather than to electrons, and it is possible to study the dependence of this effect on the concentration of majority impurities.