Abstract
Amorphous silicon based solar cells and photodetectors in TCO/p(a-SiC:H)/i(a-Si:H)/n(a-Si:H)/Al heterostructure were made by UHV-PECVD techniques using silane (SiH4) and methane (CH4) gas. A negative capacitance (NC) value was observed and attributed to a time delay between capture and injection of minority carriers at the interfaces between undoped and doped layers at high frequency. In some devices, the ideality factor (n) is higher than 2 due to tunnelling at junction interface which plays a major role. The room temperature (294 K) dark I-V result has been used during the fitting process for the proposed capacitance model. The electrical equivalent circuit model was used to simulate the dynamic behaviour of p-i-n photodetector, taking into account the presence of inductive effect with the addition of the C-d and R-d parallel circuit.