Improved surface plasmon enhanced photodetection at an AuGaAs schottky junction using a novel molecular beam epitaxy grown Otto coupling structure

Measurements of reflectivity and photocurrent as a function of angle of incidence and wavelength have been made for a GaAsAlAsGaAsAu Schottky structure based on an Otto coupling geometry which allows incident p-polarized radiation to couple to the surface plasmon (SP) mode at the AuGaAs interface. At resonance, E fields associated with the SP excitation are concentrated at the GaAsAu Schottky interface itself, enabling strong enhancement of the internal photoemission photocurrent across the Schottky barrier. Enhancement factors of the order of 20 have been achieved. A direct comparison between the resonant effects of exciting the SP at the GaAsAu Schottky junction itself and at the outer Au-air interface has been made. A simple model for the photocurrent in the device indicates that the excited photocarriers created in the gold film have a very short scattering length ϐ ≈ 10 nm, which emphasizes the importance of exciting the SP at the Schottky interface.