Paramagnetic states in μc-SiC:H thin films prepared by Hot-Wire CVD at low temperatures

The relationship between the structure, electrical conductivity and paramagnetic states in microcrystalline hydrogenated silicon carbide (μc-SiC:H) prepared by HWCVD is investigated. The study includes undoped and Al-doped (p-type) μc-SiC:H of different crystalline volume fraction (I _C^IR). High densities of paramagnetic states are observed in undoped material over a wide range of crystallinity whereas the conductivity increases by 10 orders of magnitude up to 10^-2 S/cm as the material becomes more crystalline. This dramatic increase of the conductivity attributed to unintentional n-type doping has a clear effect on the ESR spectrum which changes from a broad featureless resonance in the low crystallinity material to a sharp line with a pair of distinct satellites in highly crystalline n-type μc-SiC:H. Aldoping results in compensation and then effective p-type doping in μ c-SiC:H at higher doping concentration. Aldoping seems to hinder the crystalline growth in p-type μc-SiC:H. For I_C ^IR ≤ 20% the spin resonance signature is a broad (peak-to-peak linewidth ΔHpp ≈ 30 G) featureless slightly asymmetric line at g ≈ 2.01. The nature and behavior of the ESR spectra in different types of μc-SiC:H are investigated with respect to the Fermi level position and crystalline volume fraction.