Self-energy shifts in heavily doped, polar semiconductors

We present theoretical results for the self-energy shifts due to the interactions in a heavily doped, polar semiconductor. For the purpose of numerical demonstration we apply the results to n-type CdS. The density of states for both the majority and minority carriers are calculated in the region near the band edges. The polar coupling modifies the self-energy shifts, and new structures appear in the density of states, both above and below the Fermi level. At least some traces of these structures should be observed in experiments. Furthermore, the doping-induced band-gap narrowing is determined and we compare the obtained results with those from the much simpler so-called ${\epsilon }_0$ approximation.