Photoluminescence of n‐InN with low electron concentrations

Abstract

AbstractPhotoluminescence (PL) of n‐InN grown by molecular beam epitaxy with Hall concentrations from 3.6 × 1017 to 1.0 × 1018 cm–3 demonstrates new features as compared with that of the samples of previous generation which are characterized by a higher carrier concentration. The striking dependences of PL spectra on carrier concentration, temperature, and excitation density give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The well resolved structure consisting of three peaks was observed in the PL spectra of these samples in the energy interval from 0.50 to 0.67 eV at liquid helium and nitrogen temperatures. We attributed one of two low‐energy features of the spectra to the recombination of degenerate electrons with the holes trapped by deep acceptors with a binding energy of Eda = 0.050–0.055 eV and the other one is attributable to the LO‐phonon replica of this band. The higher‐energy PL peak is considered as a complex band formed by two mechanisms. The first one is related to the transitions of electrons to the states of shallow acceptors with a binding energy of Esh = 0.005–0.010 eV and/or to the states of Urbach tail populated by photoholes. The second mechanism contributing to this band is the band‐to‐band recombination of free holes and electrons. Relative intensities of two higher‐energy PL peaks were found to be strongly dependent on temperature and excitation power. At room temperature, the band‐to‐band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by the model calculations under the assumptions of the band gap equal to 0.665–0.670 eV at zero temperature and zero carrier concentration and the non‐parabolic conduction band with the effective mass at Γ‐point equal to 0.07 of free electron mass. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)