Plasmonic-enhanced light emission from a waveguide-integrated tunnel junction

Abstract

Light emission from inelastic electron tunneling has been demonstrated for 40 years. The ultra-fast response rate and the ultra-compact footprint make it promising for highspeed miniaturized light sources. But the application of the tunnel junction is limited by extremely low external quantum efficiency due to the low proportion of inelastic tunneling electron and wave vector mismatch between surface plasmons and photon emission. Here, we present a plasmonic-enhanced MIS (metal-insulator-semiconductor) junction coupled to a silicon waveguide with a coplanar electrode connected to a nano-antenna. The proposed tunnel junction can be fabricated using existing semiconductor planar processes to achieve controllable barrier thickness and quality for vertical current injection. Finally, an electrically driven light source with a radiation power nearly 8000 times higher than the spontaneous emission power in free space is shown to be achievable with the new structure at an operating wavelength of 1.31 μm. It is 510-fold higher than that of typical planar MIS junctions.