Absorption of p-polarised light by the metal electrode of metal-semiconductor Schottky barrier photodetectors is considerably enhanced through the excitation of surface plasmon polaritons (SPPs) at the metal-air interface. Using a prism-air gap-sample arrangement SPPs have been excited at the Al-air interface of Al-GaAs diodes, giving rise to acorresponding enhancement in device photoresponse. By adjusting the air gap dimension the coupling efficiency between incoming light and SPPs may be varied and, for large air gaps (> 1 gm), it is shown that a number of reflectance dips occur (as a function of internal angle of incidence in the prism) due to excitation of leaky guided wave modes; there are accompanying peaks in the photosignal. The potential use of SPP enhanced Schottky diodes as sensitive chemical sensors is discussed in the context of results, both experimental and computer modelled, relating to surface contamination of silver films.
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