Optical Absorption Edge Investigation of CdIn2S4 and β‐In2S3 Compounds

Abstract

AbstractCdIn2S4 and β‐In2S3 crystals are grown by direct melting of stoichiometric mixtures of their components. The absorption coefficients are measured as a function of the wavelength of the incident light between 500 to 750 nm at various temperatures. For both compounds the energy gap Eg is temperature dependent and the absorption edge shifts to lower energy values with increasing temperature. For β‐In2S3 it is found that the absorption edge is mainly due to direct transitions and the temperature dependence of Eg is linear. At room temperature the value Eg = 2.00 eV is measured. In the case of CdIn2S4 there appear indirect transitions for low values of the absorption coefficient while the temperature dependence of the direct energy gap is linear at high temperatures and quadratic at low temperatures. At room temperature the direct gap has the value Eg = 2.21 and the indirect one E = 2.05 eV. A rough estimation of the Debye temperature gives θD = 665 K.