The fundamental absorption edge of PbGa2S4

Abstract

Optical absorption spectra of PbGa2S4 are measured in the photon energy range from 2.0 to 3.2 eV and for temperatures between 32 and 300 K. PbGa2S4 is found to be an indirect-gap semiconductor with a gap energy of 2.84 eV at room temperature. At slightly higher energies the fundamental edge is followed by a direct gap with an energy of 2.91 eV at 300 K. The results obtained are compared with previous measurements and with experimental data for CdGa2S4 having similar near-edge optical properties.