Photocurrent near-field microscopy of Schottky barriers

We used a combination of internal photoemission and of near-field optical m icroscopy (SNOM) to study the lateral Variations in solid interface propert ies such as energy barriers and electron-hole recombination. Ln particular we investigated the fully formed Pt-GaP, Au-GaAs, Au-SiNx-GaAs and PtSi-Si Schottky barriers. Our approach enabled us to measure large lateral variati ons in the photocurrent with spatial resolution on the nanometric scale. Du e to the ability of SNOM to supply parallel topographic information, we obs erved photocurrent variations from zone to zone that only correlated in a f ew cases with local variations in surface morphology. We assigned the uncor related fluctuations to local variations in the interface stoichiometry, th e presence of interface states induced by the metallic overlayer and to def ect states at the junction. Furthermore, by tuning the photon energy and ap plied bias we were able to measure the surface distribution of the diffusio n length.