Theory of photoexcited and thermionic emission across a two-dimensional graphene-semiconductor Schottky junction

This paper is devoted to photocarrier transport across a two-dimensional graphene-semiconductor Schottky junction. We study linear response to monochromatic light with excitation energy well below the semiconductor band gap. The operation mechanism relies on both photoelectric and thermionic emission from graphene to a two-dimensional semiconductor under continuous illumination and zero bias. Due to the thermalization bottleneck for low-energy carriers in graphene, the photoelectric contribution is found to dominate the photoresponse at near-infrared excitation frequencies and below. The extended thermalization time provides an interesting opportunity to facilitate the interlayer photocarrier transport bypassing the thermalization stage. As a result, the total photoresponsivity rapidly increases with excitation wavelength making graphene-semiconductor junctions attractive for photodetection at the telecommunication frequency.