An investigation of electrical and optical properties of sputtered amorphous silicon nitride and germanium thin films

Low temperature preparation of thin amorphous Silicon Nitride and Germanium Films by direct RF sputter deposition was investigated. Influence of various sputtering parameters on film properties was studied. Infrared transmission spectrophotometry was used to evaluate optical properties of the films whereas electrical characteristics of the films were determined from current-voltage measurements of MIS structures. For Silicon Nitride films it was observed that the stoichiometry, as indicated by the IR transmission, dielectric constant and current density versus square root of electric field measurements, was a strong function of the sputtering gas composition and particularly the Ar/N ratio in the sputtering gas. It was established from the current-voltage relationship that the dominant conduction mechanism in these films is of PooleFrenkel type. The current-voltage characteristics of the MIS devices were observed to be independent of the electrode material, device area and the film thickness. It is concluded that the insulating films thus deposited were comparable to those deposited using any other deposition method and is anticipated that due to the low deposition temperatures, sputtering may emerge as a highly potential process for optoelectronic device passivation. Germanium Gamma-ray p-n junction detectors coated with 30 nm thick sputtered amorphous germanium exhibited improved surface stability. Hydrogenated amorphous germanium was also used and the result indicated that this material would have superior passivating properties than amorphous Germanium