Temperature dependence of the optical absorption edge in indium phosphide

M. Beaudoin, S. R. Johnson, A. J.G. De Vries, A. Mohades-Kassai, T. Tiedje

Research output: Contribution to journalConference articlepeer-review

6 Scopus citations


Optical bandgap thermometry is a new method for measuring the temperature of semiconductor substrates. In this method, the temperature of the substrate is inferred from the wavelength of the onset of transparency of the substrate which is a measure of its bandgap. Common configurations of this technique are diffuse reflectance and transmittance. In order to calibrate these spectra to substrate temperature and to better understand the temperature dependence of the absorption edge, the transmittance spectra of semi-insulating InP:Fe and n-type InP:S substrates have been measured as a function of temperature in a tube. The width of the absorption edge (Urbach parameter) is found to increase linearly with temperature from 8.7 meV at room temperature to 15.7 meV at 595°C for semi-insulating InP:Fe while it remains independent of temperature at a value of about 21.5 meV for heavily doped (6.5×1018 cm-3) InP:Fe, the temperature dependent part of the width is smaller than predicted by the standard theory where the width of the edge is proportional to the phonon population. The values of the Urbach parameter for InP:Fe are higher than those of semi-insulating GaAs which is attributed to the higher ionicity of InP.

Original languageEnglish (US)
Pages (from-to)367-372
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
StatePublished - Dec 1 1996
Externally publishedYes
EventProceedings of the 1996 MRS Spring Meeting - San Francisco, CA, USA
Duration: Apr 8 1996Apr 12 1996

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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