Leakage current reduction of metal-semiconductor-metal photodetectors by using a thin interfacial silicon dioxide layer

In this report, we show that a thin interfacial silicon dioxide layer placed between the Schottky metal and the silicon substrate reduces the leakage current of a metal-semiconductor-metal photodetector. We find the optimal interfacial oxide layer to be about 3 or 4 nm thick and is made by dry furnace oxidation of the silicon substrate at 800 degrees C, taken from a 0.18 mu m CMOS process normally used to make the gate oxide. As compared to a metal-semiconductor-metal detector without this oxide layer, we measure a factor 5 reduction in leakage current density to 18 mu A/cm(2) at 5 V, a weaker increase in dark current with bias, and a factor 3 improvement in photoresponsivity to 0.35 A/W at 635 nm wavelength. Additionally, we compare Schottky barrier height, effective Richardson constant, and capacitance measurements between photodetectors made with and without this interfacial oxide.