Defect densities in tetrahedrally bonded amorphous carbon deduced by junction capacitance techniques

Junction capacitance measurements performed on tetrahedrally bonded amorphous carbon (ta-C)/crystalline-Si (c-Si) heterostructures are used to deduce the defect density in thin ta-C films. Using the drive level capacitance profiling technique, we determine a homogeneous defect density of 6±1.5×1017 cm−3 in the undoped (p-type) ta-C films and one order of magnitude larger in the nitrogen-doped (n-type) films. Admittance measurements reveal defect states at the ta-C/c-Si interface with a density exceeding 2×1012 cm−2.