Theoretical and experimental demonstration of high-performance near-infrared thin-film Schottky barrier photodetectors

Abstract

Hot carrier harvesting with a metal-semiconductor Schottky junction, often called as internal photoemission (IPE), has been a promising candidate for semiconductor-based sub-bandgap photodetection in the near-infrared wavelengths for many emerging applications such as imaging, sensing, and photocatalysis. However, there is a distinct limitation that the external quantum efficiency (EQE) of IPE is very low. To overcome this problem, numerous studies have been focused on plasmonic effects to enhance optical absorption in the vicinity of metal/semiconductor interfaces. Despite these efforts, the limitation has not been fully addressed by only improving optical absorption without a complete understanding of the IPE system. Accordingly, comprehensive understanding and quantitative analysis of its complex dynamics are necessary. In this dissertation, we demonstrate a rigorous theoretical model for a simple one-dimensional IPE system that can describe the dynamics of the IPE system and provide quantitative loss mechanism analysis, and we experimentally verify our model using planar thin-film Schottky barrier photodetectors (SBPDs). Our model shows that optical absorption is responsible for only a part of the entire IPE process and other transport mechanisms should be carefully considered in a wholistic manner, indicating the importance of quantitative loss mechanism analysis. Guided by the model, our patternless silicon-based thin-film SBPDs achieve EQEs higher than previously reported nano-patterned SBPDs.