Properties of semiconducting rhenium silicide thin films grown epitaxially on silicon (111)

The optical and transport properties of rhenium silicide thin films epitaxially grown on Si(111) have been studied. On the one hand, the analysis of the optical spectrum above the band gap energy confirms the semiconducting character of the samples. Moreover, the absorption coefficient prefactor measured for films of various thicknesses in the range of 50–475 Å depend on the thickness itself, possibly reflecting a two-dimensional quantization of states related to the existence of a quantum well due to the band offsets at the heterojunction. On the other hand, electrical measurements on high resistivity silicon substrates are explained by the existence of an impurity band. The concentration of electrically active impurities decreases by one order of magnitude when the sample is annealed at 850°C under a hydrogen partial pressure.