Majority-carrier mobility on germanium surfaces

Measurements are reported of the majority-carrier surface mobility at several temperatures and following various etches in a large number of both n- and p-type germanium samples and the results are compared with theoretical calculations based on the diffuse scattering model. The pulsed field-effect technique is used, advantage being taken of the relatively slow thermal release of charge from most of the surface states into the majority-carrier band at reduced temperatures. The results indicate good qualitative agreement with the diffuse scattering model, but some degree of specularity is necessary to account for the data obtained. The less-than-predicted sensitivity to such parameters as impurity concentration and temperature as well as the marked effect of etchants may very well be the results of the overriding influence of surface states and their variation with surface treatment.