Fabrication of electrically contacted plasmonic Schottky nanoantennas on silicon

Abstract

We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physical model for the internal photoemission of hot carriers, photons coupled onto the Au nanoantennas excite resonant plasmons, which decay into energetic “hot” holes emitted over the Schottky barrier at the Au/p-Si interface, resulting in a photocurrent. In our device, the active Schottky area consists of Au/p-Si contact and is very small, whereas the probing pad for external electrical interconnection is larger but consists of Au/Ti/p-Si contact having a comparatively higher Schottky barrier, thus producing negligible photo and dark currents. We describe fabrication that involves an electron-beam lithography step overlaid with photolithography. This highly compact component is very promising for applications in high-density Si photonics.