Semiconductors are well known as efficient materials for optical energy conversion but are limited by their bandgap, below which they do not absorb light. Hot carrier generation in a metal contact can reduce the bandgap limitation to the Schottky barrier height at the metal-semiconductor interface because of carrier injection into the base semiconductor. However, for efficient photodetection the metal must be highly absorptive at long wavelengths and ultra-thin in order for the hot carriers to reach the Schottky interface with enough energy to traverse the barrier. This has been achieved using costly lithography processes to create plasmonic resonances in the metal that non-radiatively decay into hot carriers. However, we demonstrate a cost effective, lithography free method of obtaining high sub-bandgap absorption and subsequent photocurrent generation in an ultra-thin film back contact to silicon by choosing metals with optical properties that satisfy a zeroth order Fabry-Perot resonance condition.

Hot carrier photodetectors using inorganic semiconductors with nanometer-scale metallic optical coatings

254th National Meeting (2017)

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