aDepartment of Electrical and Electronics Engineering, Atilim University, 06836 Ankara, Turkey
bDepartment of Physics, Middle East Technical University, 06531 Ankara, Turkey
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 β = 95.03°. 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 γ = ?3.53 × 10?4 eV/K.