Abstract
The ionization energy of an electron bound to a donor atom is calculated as a function of the number of electrons in the conduction band and the temperature assuming Thomas-Fermi screening. The results are compared with a previous numerical calculation performed for InSb. We also show that it is possible to induce a Mott transition by applying stress to a degenerately doped many-valley semiconductor, with a resulting change from a metallic to an insulating phase.