OPTICAL AND ELECTRICAL PROPERTIES OF AMORPHOUS (GeS2)100-xGax THIN FILMS

Results from the study of basic optical and electrical parameters of semiconducting (GeS2)100-xGax (x=0, 4, 8, 12 at.%) amorphous layers have been summarized. The investigation of the optical absorption has shown that the introduction of Ga leads to a shift in the absorption edge towards lower energies in comparison with GeS2. The spectral distribution of the refractive index n, accounting the influence of photoexposure, has been specified. The optical energy gap Egopt has been determined from the Tauc plot αhν=B(Egopt-hν)2. The electrical energy gap Egel has been obtained from the thermal dependence of the conductivity. Both the values of Eg decrease with increasing Ga content. From the current-voltage characteristics, the effective electron mass m in the conduction band, the electron work function χ at the Al/Ge-S-Ga interface and the relative dielectric permitivity ε have been determined. The experimental data are in agreement with Christov’s theory for injected electron currents into dielectric or semiconducting materials. The observed regularities are related to some structural peculiarities in the Ge-S-Ga system studied