Temperature variation of energy gap values in CuGaSnSe4

Measurements of reflectance as a function of temperature from 4 to 300 K have been made on a single crystal sample of CuGaSnSe4 using light polarised (a) perpendicular and (b) parallel to the c axis of the crystal. Values of the energy gaps EA, EB, and EC between the three valence bands and the conduction band have thus been determined as a function of temperature. The variation of these energy gaps with temperature has been fitted to the equation proposed by Manoogian and Leclerc, i.e., E0 − E = UTs + Vθ(coth (θ/2T) − 1). Values of spin–orbit splitting Δso and crystal field splitting Δcf have been determined and the temperature variation of these explained in terms of contributions from d orbitals to the valence band. Values of the various spin–orbit splittings and deformation potentials are discussed.