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Title: Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method

Abstract

The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectra of Sn-doped In{sub 2}O{sub 3} (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In{sub 2}O{sub 3} single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.

Authors:
;  [1];  [2]
  1. Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208 (United States)
  2. Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States)
Publication Date:
OSTI Identifier:
22584176
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 240; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ABSORPTION SPECTRA; DOPED MATERIALS; EXCITATION; INDIUM OXIDES; MONOCRYSTALS; PHOTOLUMINESCENCE; POLYCRYSTALS; SEMICONDUCTOR MATERIALS; THIN FILMS

Citation Formats

Dolgonos, Alex, Mason, Thomas O., and Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu. Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method. United States: N. p., 2016. Web. doi:10.1016/J.JSSC.2016.05.010.
Dolgonos, Alex, Mason, Thomas O., & Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu. Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method. United States. doi:10.1016/J.JSSC.2016.05.010.
Dolgonos, Alex, Mason, Thomas O., and Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu. Mon . "Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method". United States. doi:10.1016/J.JSSC.2016.05.010.
@article{osti_22584176,
title = {Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method},
author = {Dolgonos, Alex and Mason, Thomas O. and Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu},
abstractNote = {The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectra of Sn-doped In{sub 2}O{sub 3} (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In{sub 2}O{sub 3} single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.},
doi = {10.1016/J.JSSC.2016.05.010},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 240,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}