Study on the photoelectric hot electrons generation and transport with metallic-semiconductor photonic crystals

Abstract

Photoelectric hot carrier generation in metal-semiconductor junctions allows for optical-to- electrical energy conversion at photon energies below the bandgap of the semiconductor. Which opens new opportunities in optical sensors and energy conversion devices. In this thesis research, the wafer-scale metallic-semiconductor photonic crystal (MSPhC) has been designed for photoelectric hot electrons collection. The periodic nano-cavities structure of MSPhC supports various optical modes that can resonate with light in broad wavelength region. Optical simulation and experimental results of MSPhC have been demonstrated. The simulation results shows MSPhC can achieve up to 70% absorption in the solar radiation range, with ultra-thin metal film. Experimentally, MSPhC has fabricated via 6" Si wafer scalable microfabrication techniques. A broadband sub-bandgap hot electron response with a full width at half maximum (FWHM) of 235 nm centered at 590 nm is observed. Photoresponse enhancement factor of 12.28 at 639 nm compared to a flat chip is also measured. Applications of these results could lead to low-cost and robust photoelectrochemical device such as full-spectrum solar water splitting.