PHOTOCONDUCTIVITY AND FUNDAMENTAL ABSORPTION-EDGE FOR GALLIUM SESQUISULFIDE SINGLE-CRYSTALS

Photoelectric properties have been investigated on Ga2S3 single crysta ls prepared from melt. Effect of light intensity, applied voltage and ambient temperature on the spectral distribution of photoconductivity and the life time of carriers have been studied. Form of the spectral characteristics has been found practically independent of the light in tensity and the applied bias voltage, but it shifted to higher values of the photocurrent with increasing light intensity and applied bias v oltage. Photocurrent decreases with the increase of temperature up to 200 K and increases after this temperature. The (E(g) - T) behaviour i s in agreement with behaviour described by the Varshni equation and it s constants found to be alpha = 6,021 x 10(-4) eVK(-1), beta = -167 K and the temperature coefficient dE(g)/ dt= - 5.33 x 10(-4) eVK(-1). Li fe time tau decreases with the increase of light intensity and applied voltage, the life time increases with decreasing the temperature and under 200 K the life time decreases with increasing temperature. Optic al absorption of Ga2S3 single crystals has been investigated in the re gion of the fundamental absorption edge and the near-infrared over the temperature range 77-300 K. The direct band gap of the Ga2S3 single c rystals is found to be 2.45 eV at room temperature. Peak has been obse rved at photon energy equal to 2.38 eV in the absorption spectrum of t he Ga2S3 single crystals at low temperature only.