Transport studies of carbon-rich a-SiC_x:H film through admittance and deep-level transient spectroscopy measurements

Abstract

An intrinsic, carbon-rich a-SiC _x :H thin film, prepared by the plasma-enhanced chemical vapour deposition (PECVD) technique, has been studied mainly by AC admittance and small-pulse deep-level transient spectroscopy (DLTS) measurements on an Al/a-SiC _x :H/p-Si metal–insulator–semiconductor (MIS) structure. The effects of measurement temperature, voltage and small-signal AC modulation frequency on the MIS capacitor are qualitatively and quantitatively described. The kinetics of charge injection from the silicon substrate into the a-SiC _x :H film, as a function of temperature and voltage bias stresses, are reported. Nearest-neighbour and variable-range hopping mechanisms are considered. An activation energy of ∼ 0.09 eV, and a density of states (DOS) of about 10¹⁹ cm⁻³/eV were found. The value of the DOS is in agreement with the effective interface DOS of above 10¹² cm⁻²/eV assessed by both capacitance and DLTS measurements. The frequency (or temperature) dependence of the MIS capacitor over the whole DC voltage range is considered in detail. Single- and double-step carrier exchange mechanisms between the a-SiC _x :H film and the silicon substrate, in the accumulation and depletion voltage regimes, respectively, are proposed.

Acknowledgements

This work was carried out with the financial support of both the State Planning Organization (BAP:01-05-DPT 2002 K 12 0540-15) and Turkish Scientific and Technical Research Council (TUBITAK-BAYG-BDP).