It is shown that in doped zero-gap semiconductors like $\alpha -\mathrm{Sn}$, the intraband part of the static screening function is considerably decreased from that of free electrons at large momentum transfer by the $p$-like character of the conduction-band wave function. However, it is also shown that this large screening loss produces a relatively small change in the ionized-impurity-limited mobility.

• Received 26 October 1970

DOI:https://doi.org/10.1103/PhysRevB.4.664