Electrical transport mechanisms in p(+)a-SiC:H/n c-Si heterojunctions: Dark J-V-T characteristics

In the present paper we show results of dark current-voltage measurements performed on p(+) a-SiC:H/n c-Si heterojunction diodes at various temperatures (100-400K). We investigated the voltage derivative of these J-V curves in order to the distinguish possible current transport mechanisms. It was found that for low temperatures (<300K), the current is determined by recombination of carriers in the crystalline silicon, whereas at high temperature (>300K), by a tunnelling mechanism. At room temperature, both mechanisms contribute to the current. By using an equivalent circuit model and detailed numerical simulations we have interpreted our experimental characteristics. The simulations done at room temperature, show that at low forward bias voltage the current is controlled by recombination in the crystalline silicon and that at high forward bias voltage by a combination of multi-step tunnelling and a-SiC:H series resistance. For interface state densities equal to or higher than 10(12) cm(-2), the recombination was found to be dominated by the states at the amorphous-crystalline silicon interface.