Localized and Delocalized Characters in Optical Spectra of Interacting Donors in Semiconductors

Abstract

Optical absorption spectra in low and intermediate concentrations of donor impurities are calculated by taking account of the excitonic interaction between a hole localized on a donor and a D - ion. In calculating absorption spectra, the self-consistent Born approximation is adopted. in order to treat both diagonal and off-diagonal disorder due to random distribution of donors, which appears in the excitonic and transfer terms of D - states in the final state Hamiltonian, respectively. The interplay between excitonic and transfer effects in absorption spectra is investigated. It is shown that the broadening behavior of peaks in high energy region is due to transfer effect between donor excited states and delocalized exciton states while the broad tail in low energy region corresponds to the inhomogeneous broadening of the transitions to localized exciton states.