Efficient, broadband and wide-angle hot-electron transduction using metal-semiconductor hyperbolic metamaterials

Highlights: • A "stereo" hot-electron device based on hyperbolic metamaterials is presented. • Results show broadband and omnidirectional enhancement in external quantum efficiency. • Results show great potential in energy-efficient, sub-bandgap photodetectors, spectrometers, and plasmonic sensors. • Applicability of hot-electron devices to energy harvesting is evaluated. Hot-electron devices are emerging as promising candidates for the transduction of optical radiation into electrical current, as they enable photodetection and solar/infrared energy harvesting at sub-bandgap wavelengths. Nevertheless, poor photoconversion quantum yields and low bandwidth pose fundamental challenges to fascinating applications of hot-electron optoelectronics. Based on a novel hyperbolic metamaterial (HMM) structure, we theoretically propose a vertically-integrated hot-electron device that can efficiently couple plasmonic excitations into electron flows, with an external quantum efficiency approaching the physical limit. Further, this metamaterial-based device can have a broadband and omnidirectional response at infrared and visible wavelengths. We believe that these findings may shed some light on designing practical devices for energy-efficient photodetection and energy harvesting beyond the bandgap spectral limit.