Optical and Photoelectrical Properties of Reactive RF-Sputtered Amorphous Nitrogen-Doped SiC Thin Films

Abstract

Amorphous nitrogen-doped silicon carbide thin films were deposited by RF magnetron sputtering from a SiC target in an Ar/N2 atmosphere, and their structural, optical, and photoelectrical properties were investigated. The successful presence of nitrogen in the SiC-based film was confirmed by EDS analysis. Raman spectroscopy revealed a broad and asymmetric feature centered at approximately 1500 cm−1 , characteristic of a highly disordered carbon-related structure and consistent with the amorphous nature of the film. The deconvolution of the Raman spectrum into the D and G bands yielded an intensity ratio of ID/IG ≈ 0.91, further indicating a substantial degree of structural disorder within the carbon-related bonding environment. The optical response was analyzed using a Tauc–Lorentz model and a band-fluctuations approach. A film thickness of ∼ 230 nm, an optical band gap of Eg = 1.70 eV, and an Urbach energy of 0.23 eV were obtained, evidencing a broad absorption tail associated with substantial structural and electronic disorder. Current–voltage measurements performed using Al contacts showed a strongly asymmetric electrical response between positive and negative bias. Under illumination, the current increased markedly at positive bias, reaching a photo-to-dark current percentage photoresponse of ∼3600%, indicating a pronounced photoresponse and promising potential for optoelectronic applications. The pronounced bias dependence and photoresponse also are consistent with photocarrier generation and transport involving the a-SiC layer and the p-Si/a-SiC interface. These results demonstrate that sputtered a-SiC thin films exhibit strongly tunable photoelectrical transport associated with structural disorder, localized states, and heterointerfacial effects.

Keywords: SiC dopado; Sputtering; Propiedades Optoelectronicas