Modeling the effects of surface plasmon resonance on hot electron collection in a metallic-semiconductor photonic crystal device

Abstract

Metallic-semiconductor Schottky hot carrier devices have been found as a promising solution to harvest photon with energy below the bandgap of semiconductor, which is of crucial importance for realizing efficient solar energy conversion. In recent years, extensive efforts have been devoted to utilizing surface plasmon resonance to improve light absorption by creating strong light-metal interaction, which generates hot electrons through nonradiative decay. However, how surface plasmon enhances the efficiency of hot electron collection is still debatable. This thesis studies the effects of surface plasmon resonance on hot electron collection in a metallic-semiconductor photonic crystal (MSPhC) designed by our group for efficient photoelectron-chemical energy conversion. In contrast to a broadband light absorption at the range from 400 nm to 800 nm, the sub-bandgap photoresponse shows a single peak centered at 590 nm, which is identified as the surface plasmon resonant wavelength of this device. We develop a theoretical model of hot electron generation, transport and injection in this device incorporating the effects of anisotropic hot electron momentum distribution caused by surface plasmon resonance. Near resonant wavelength, surface plasmon dominates the electric field in the thin Au layer, which generates hot electrons with high enough momentum preferentially normal to the Schottky interface. Through analyzing the energy, momentum and spatial distribution of generated hot electrons, we develop a model to estimate the internal quantum efficiency (IQE) of this device. The anisotropic hot electron momentum distribution largely enhances IQE and photoresponse near the resonant wavelength. Compared with the widely used Fowler's theory of Schottky internal photoemission, our model can better predict IQE of surface plasmon assisted hot electron collection. Combined with large scale photonic design tools, this quantum-level model could be applied for tuning and enhancing photoresponse of Schottky hot carrier devices.