Analysis of frequency- and temperature-dependent interface states in PtSi/p-Si Schottky diodes

To yield quantitative information about their interface states, PtSi/p-Si Schottky structures have been studied using conductance and capacitance measurements over a wide range of frequencies (1 kHz to 1 MHz) and at several temperatures (80-140 K). The increase in capacitance at lower frequencies is seen as a signature of interface states, the densities of which are evaluated to be of the order of ∼10¹² eV^-1 cm^-2. The presence of interface states is also evidenced as a peak in the conductance-frequency characteristics that increases in magnitude with decreasing temperatures. The variations of interface conductance are best described by an analytical equation derived assuming an energy-dependent cross-section of these interface states. The conductance data is subsequently used to extract the relaxation times of interface states and their energy distribution with respect to the top of the valence band. Relaxation times, in particular, while temperature dependent with an average value of ∼4 μs, show a noticeably weak dependence on bias.