An Direct Comparison of Plasmonic and Interband Hot Carrier Generation

Bob Zheng ECE, Rice University, Houston, Texas, USA Laboratory for Nanophotonics, Rice University, Houston, USA Hangqi Zhao ECE, Rice University, Houston, Texas, USA Laboratory for Nanophotonics, Rice University, Houston, USA Alejandro Manjavacas Physics and Astronomy, Rice University, Houston, USA Laboratory for Nanophotonics, Rice University, Houston, USA Michael McClain Chemistry, Rice University, Houston, USA Laboratory for Nanophotonics, Rice University, Houston, USA Peter Nordlander Physics and Astronomy, Rice University, Houston, USA Laboratory for Nanophotonics, Rice University, Houston, USA Naomi Halas ECE, Rice University, Houston, Texas, USA Physics and Astronomy, Rice University, Houston, USA Chemistry, Rice University, Houston, USA Laboratory for Nanophotonics, Rice University, Houston, USA

Hot carrier generation in metallic nanostructures offers a potential route to circumventing thermodynamic efficiencies of traditional light-harvesting devices and structures. However, previous experimental realizations of hot electron devices have shown low photo-conversion efficiencies. Several theoretical works have sought to understand the fundamental processes behind hot carrier generation and explore routes toward increasing the carrier generation efficiency. In this work, we discriminate between hot carrier generation from interband transitions and surface plasmons by comparing photocurrent generation in Schottky and ohmic devices. We show that plasmonic hot carrier generation results in high energy hot carriers while hot carriers from interband transitions result in low energy carriers. We also show that plasmonic hot carrier generation depends on the field intensity enhancement and independent of interband absorption. This work definitively shows that plasmonic hot carrier generation is not explained by heating and shows that injection of hot carriers over an energy barrier explicitly requires surface plasmon decay. Our results also show a surprising deviation from Fowler theory, which indicates that surface plasmons preferentially excite electronic states near the Fermi level. This work paves the way for more efficient hot electron devices and could lead to the development of novel optoelectronic devices.

byz1@rice.edu