The composition dependence of the optical properties of InN-rich InGaN grown by MBE

Abstract

ABSTRACTStudy of the relationship between the composition and optical energies of InxGa1-xN has generated much interest and intrigue over the last decade and beyond. In this paper we describe data from InxGa1-xN epilayers covering the full range of composition (0 < × < 1), grown by both Metal-Organic Vapour Phase Epitaxy (MOVPE) and Molecular Beam Epitaxy (MBE). In particular we concentrate on a set of state-of-the-art InN rich MBE layers (0.6 < × < 1.0). Wavelength dispersive X-ray microanalysis is employed for accurate measurement of the InN fraction and of the group III : group V ratio. The InN rich layers are shown to be highly stoichiometric. The composition results are correlated with luminescence spectra, which show peaks covering the range 1.3 to 0.7 eV. Inclusion of our data from sets of MOVPE and MBE epilayers with InN fractions up to 0.4, measured using identical techniques, allows the composition dependence of the luminescence peak energy to be plotted across the entire composition range. A quadratic fit gives good agreement with both the low-InN MOVPE and high-InN MBE samples but not for the intermediate region. Possible reasons for this are discussed.