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 (mu c-SiC:H) prepared by HWCVD is investigated. The study includes undoped and Al-doped (p-type) mu c-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 mu c-SiC:H. Al-doping results in compensation and then effective p-type doping in mu c-SiC:H at higher doping concentration. Al-doping seems to hinder the crystalline growth in p-type mu c-SiC:H. For I-C(IR) <= 20% the spin resonance signature is a broad (peak-to-peak linewidth Delta H-pp approximate to 30 G) featureless slightly asymmetric line at g approximate to 2.01. The nature and behavior of the ESR spectra in different types of mu c-SiC:H are investigated with respect to the Fermi level position and crystalline volume fraction. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim