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Crystal data and indirect optical transitions in Tl2InGaSe4 crystals

Authors: 
Qasrawi, A. F.
Gasanly, N. M.
Journal Name: 
MATERIALS RESEARCH BULLETIN
Volume: 
43
Issue: 
6
Pages From: 
1497
To: 
1501
Date: 
Tuesday, June 3, 2008
Keywords: 
semiconductors; crystal growth; X-ray diffraction; optical properties
Abstract: 
The room temperature crystal data and the optical properties of the Bridgman method grown Tl2InGaSe4 crystals are reported and discussed. The X-ray diffraction technique has revealed that Tl2InGaSe4 is a single phase crystal of monoclinic structure. The unit cell lattice parameters, which were recalculated from the X-ray data, are found to be a = 0.77244 nm, b = 0.64945 nm, c = 0.92205 nm and beta = 95.03 degrees. The temperature dependence of the optical band gap of Tl2InGaSe4 single crystal in the temperature region of 290-500 K has also been investigated. The absorption coefficient was calculated from the transmittance and reflectance data in the incident photon energy range of 1.60-2.10 eV. The absorption edge is observed to shift toward lower energy values as temperature increases. The fundamental absorption edge corresponds to indirect allowed transition energy gap of 1.86 eV that exhibited a temperature coefficient gamma = -3.53 x 10(-4) eV/K. (C) 2007 Elsevier Ltd. All rights reserved.