On the density-of-states function in heavily doped compound semiconductors

We study the energy spectrum of the conduction electrons and the corresponding density-of-states (DOS) in heavily doped compound semiconductors forming band-tails. It is found, taking Hg1 -xCdxTe as an example, that the complex nature of the energy spectrum, the oscillatory DOS for negative values of the energy and the formation of a new forbidden zone is due to interaction of the impurity atoms in the tail with the spin-orbit splitting constant of the valence band. No oscillations in the DOS are found for heavily doped two-band Kane type and parabolic energy bands, respectively. The well-known results have also been obtained from our generalized derivation under certain limiting conditions. (C) 2001 Elsevier Science B.V. All rights reserved.