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2009
Journal Article
Titel
Observation of Fermi-edge and excitons and exciton-phonon complexes in the optical response of heavily doped n-type wurtzite GaN
Alternative
Nachweis von Exzitonen nahe der Formi-Kante sowie von Exzitonen-Phononen-Komplexen in der Dielektrischen Funktion von hoch dotierten, hexagonalen GaN-Schichten
Abstract
We present the imaginary part of the dielectric function of n-type wurtzite GaN measured by spectroscopic ellipsometry in the spectral range of 3.2-4.5 eV at room temperature for electron concentrations from 1x10(16) to 2.3x10(19) cm(-3). The observed behavior is consistent with the Mott density of about 2x10(18) cm(-3). The comprehensive line-shape analysis demonstrates the importance of excitonic effects over the whole doping range. For low electron concentrations, we observe contributions from discrete excitons, Coulomb enhanced band-to-band (BB) optical transitions, and transitions into exciton-phonon complexes (EPCs). For degenerate GaN, along with the BB transitions, we identify Fermi-edge excitons as well as a significant enhancement of the optical response due to EPCs. States with different numbers of phonons (from one to approximately ten) are active in such optical transitions in heavily doped GaN.
Author(s)