ANALYSIS OF SURFACE-PLASMON POLARITON ENHANCEMENT IN PHOTODETECTION BY AL-GAAS SCHOTTKY DIODES

The surface plasmon polariton mediated photoresponse from Al-GaAs diod es is examined in a prism-air gap-diode configuration as a function of both the wavelength of the incident light and thickness of the Al ele ctrode. The experimental data shows a pronounced dip in reflectance as a function of internal angle of incidence in the prism, due to the ex citation of the surface plasmon polariton at the Al-air interface, and a corresponding peak in device photosignal. Careful modelling of refl ectance and quantum efficiency data shows that the bulk of the signal is generated by light which is re-radiated from this surface mode into the semiconductor substrate where it is absorbed by the creation of e lectron-hole pairs in the depletion region. This holds for all the wav elengths used here (all are shorter than the GaAs absorption edge) and across the thickness range of the Al electrodes (20-50 nm). Quantum e fficiencies in the range 0.5-22% and enhancement factors of typically 7.5 were recorded in this investigation.