Influence of defects on the absorption edge of InN thin films: The band gap value

J. S. Thakur, Y. V. Danylyuk, D. Haddad, V. M. Naik, R. Naik, and G. W. Auner
Phys. Rev. B 76, 035309 – Published 9 July 2007

Abstract

We investigate the optical-absorption spectra of InN thin films whose electron density varies from 1017to1021cm3. The low-density films are grown by molecular-beam-epitaxy deposition while highly degenerate films are grown by plasma-source molecular-beam epitaxy. The optical-absorption edge is found to increase from 0.61to1.90eV as the carrier density of the films is increased from low to high density. Since films are polycrystalline and contain various types of defects, we discuss the band gap values by studying the influence of electron degeneracy, electron-electron, electron-ionized impurities, and electron-LO-phonon interaction self-energies on the spectral absorption coefficients of these films. The quasiparticle self-energies of the valence and conduction bands are calculated using dielectric screening within the random-phase approximation. Using one-particle Green’s function analysis, we self-consistently determine the chemical potential for films by coupling equations for the chemical potential and the single-particle scattering rate calculated within the effective-mass approximation for the electron scatterings from ionized impurities and LO phonons. By subtracting the influence of self-energies and chemical potential from the optical-absorption edge energy, we estimate the intrinsic band gap values for the films. We also determine the variations in the calculated band gap values due to the variations in the electron effective mass and static dielectric constant. For the lowest-density film, the estimated band gap energy is 0.59eV, while for the highest-density film, it varies from 0.60to0.68eV depending on the values of electron effective mass and dielectric constant.

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  • Received 3 May 2006

DOI:https://doi.org/10.1103/PhysRevB.76.035309

©2007 American Physical Society

Authors & Affiliations

J. S. Thakur1,*, Y. V. Danylyuk1, D. Haddad2, V. M. Naik3, R. Naik2, and G. W. Auner1

  • 1Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202, USA
  • 2Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201, USA
  • 3Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA

  • *jagdish@wayne.edu

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Vol. 76, Iss. 3 — 15 July 2007

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