We present a systematic experimental investigation of the photoluminescence of heavily doped, compensated Si:P,B. The spectra broaden as the doping levels are increased, as expected. The spectral weights of the no-phonon peak and the phonon-assisted transitions vary with compensation and with excitation intensity. In contrast with the simple superposition of high-level and low-level spectra found for uncompensated material, increasing the input power for heavily doped, compensated Si produces a strong, continuous shift in energy of the entire spectrum in an essentially rigid way. A logarithmic power dependence found for the two most heavily doped samples is consistent with an exponential band tail. Deviations from this behavior are found for two samples with lower concentration and compensation. We suggest that these deviations may signal the onset of a minimum in the density of states that occurs when the acceptor (donor) band begins to separate from the host valence (conduction) band as the dopant concentration is reduced.

• Received 4 October 1993

DOI:https://doi.org/10.1103/PhysRevB.49.1677