Photon induced negative capacitance in metal oxide semiconductor structures

Design and fabrication of photon induced, negative capacitance in a Metal Oxide Semiconductor (MOS) capacitor is presented, where a non-ferroelectric material serves as the gate dielectric. The underlying device physics involves states at the semiconductor-oxide interface, coupled with the injection of photo-generated electrons. This forces the otherwise increasing surface potential to decrease in response to an increase in the gate voltage; and causes the total capacitance in depletion mode to be greater than the geometrical capacitance at room temperature. We find the occurrence and value of the negative capacitance to depend on the interface trap density, and light intensity.