Approaches for Optimizing Near Infrared Si Photodetectors Based on Internal Photoemission

Backside illuminated Si Schottky barrier photodetectors facilitating the effect of internal photoemission are a promising candidate to extend the detection range of Si photodetectors in the short-wavelength infrared range. The detectivity – a merit that is usually limited for planar Schottky photodetectors – can be improved by photonic nanostructures like pyramids that offer a path to increase responsivity and reduce dark currents. We took two approaches based on nanopyramids and investigated their potential to improve the detectivity. By partially metalizing the pyramid, a reduction in dark current is expected; through optimizing the structural parameters, the reflection from the device can be diminished. Using an easy-to-access geometrical explanation as well as finite-difference time-domain simulation, we derived basic design rules and the limitation in improvement one can expect from these approaches.