We have studied the disappearance of impurity levels in silicon and germanium due to free‐carrier screening of the Coulomb field of the impurity ions. The ground‐state eigenfunctions and eigenvalues have been calculated for electrons described by an ellipsoidal effective‐mass Hamiltonian. A two‐dimensional finite‐element analysis was used to obtain the solutions. Only moderate carrier densities (1019cm−3for silicon and 1018cm−3for germanium) are needed to cause the impurity levels to disappear into the conduction band, the result at high doping densities being simply a degenerate semiconductor.