Photosensing by Edge Schottky Barrier Height Modulation Induced by Lateral Diffusion Current in MOS(p) Photodiode

Metal-oxide-semiconductor (MOS) photodiode was examined under illumination of 30, 50, and 70 mW/cm². By measuring devices with different oxide thicknesses, we found that the light current increases as the oxide thickness increases. We suggest that the light current is caused by edge Schottky barrier height modulation of holes induced by photogenerated lateral electron diffusion current and the saturated light current is perimeter dependent. The pinned oxide electric field for current saturation can reach 1.404 MV/cm at the edge of device and the sensitivity of MOS photodiode with oxide thickness of 1.9 nm is up to 20360 under irradiance of 70 mW/cm².