Near band-gap photoluminescence of InN due to Mahan excitons

The luminescence spectrum of degenerately n-type doped hexagonal InN extends to energies significantly higher than the renormalized band edge of the material. The line shape cannot be explained by simple band-filling. Reflectivity spectra reveal at low temperatures a strongly enhanced intensity at the Fermi energy which we ascribe to a Fermi edge singularity of the electrons interacting with holes to form so-called Mahan excitons. High k-values of the holes recombining with Fermi edge electrons are provided by localization at acceptors. A weak binding energy for a Mahan exciton is expected due to screening of the electron liquid in the conduction band. The concept of Mahan excitons allows us to understand the observed near band gap photoluminescence spectra. [GRAPHICS] . (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim