Concentration Dependence of Excitation Spectrum of Donors

The concentration dependence of the excitation spectra of donors is investigated theoretically, in the low concentration region of the impurity conduction. A new interpretation of the broadening mechanism of the excitation spectra is presented, according to which the interaction of excited donor states with the so-called D - band formed by the surrounding neutral donors plays an important role. The analysis of the isolated line and the continuous spectrum of the absorption is made separately. The comparison with the experimental result of the absorption spectra for arsenic donors in germanium is made.