Optical energy-gap variation and deformation potentials in CuInTe2

Abstract

Values of optical energy gap E0 as a function of pressure P up to 3 GPa at room temperature, and as a function of temperature T in the range 10–300 K at atmospheric pressure were obtained by optical-absorption measurements on samples of CuInTe2. It was shown that in this pressure range, E0 varies linearly with P, dE0/dP having a value of 2.2×10−2 eV/GPa. The variation of E0 with T was fitted well by a simple Manoogian–Leclerc equation of the form E0(0) − E0(T) = UT + Vφ (coth φ/2T−1). Both dE0/dP and U can be related to (dE0/dT)2, the lattice dilation contribution to the variation of the energy gap with temperature, and the values obtained in the two cases showed good agreement. The Vφ term can be related to (dE0/dT)1, the energy-gap variation due to electron-phonon interaction. From the values of (dE0/dT)1 and (dE0/dT)2, values were determined for the acoustic deformation potentials of the conduction band Ce and of the valence band Ch.