Temperature dependence of electron mobility in doped n-Ge

In this work we point out experimentally the anomalous behavior of the tota l mobility as a function of temperature for a specified doped n-Ge sample. Three perfect Ge crystals were grown, with As and Ga as donor and acceptor impurities, with suitable concentrations in one of the crystals, in order t o satisfy the condition which is imposed by a theoretical model e.g. 5 x 10 (-2) < N-A/N-D < 0.33 and N-D + N-A > 8 x 10(13) cm(-3) Therefore for this specified crystal the mobility reaches at T = 9 K a maximum, at T = 23 K it reaches a minimum, at T = 25 K it increases according to T-3/2 law, and th en decreases monotonously according to T-3/2 law due to the phonon scatteri ng. In contrast in the other two samples, the mobilities first increase mon otonously and then at 18 K and at 26 K decrease monotonously due to the T-3 /2 law.