Detection of infrared photons using the electronic stress in metal-semiconductor cantilever interfaces

We report on a new method for detecting photons using the stress caused by photoelectrons emitted from a metal film surface in contact with a semiconductor microstructure which forms a Schottky barrier. The detection of photons results from measuring the photo-induced bending of the Schottky barrier microstructure due to electronic stress produced by photoelectrons diffusing into the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due to electronic stress. In this work we studied the photon response of 500 nm thick Si microcantilevers coated with a 30 nm layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interface which diffuse into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to contract in length but not the Pt layer, the bimaterial microcantilever bends. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength lambda = 1550 nm. (C) 2000 Elsevier Science B.V. All rights reserved.