Micromechanical Uncooled Photon Detectors

Recent advances in micro-electro-mechanical systems (MEMS) have led to the development of uncooled infrared detectors operate as micromechanical thermal detectors or micromechanical quantum detectors. The authors report on a new method for photon detection using electronic (photo-induced) stresses in semiconductor microstructures. Photo-induced stress in semiconductor microstructures, is caused by changes in the charge carrier density in the conduction band and photon detection results from the measurement of the photo-induced bending of semiconductor microstructures. Small changes in position (displacement) of microstructures are routinely measured in atomic force microscopy (AFM) where atomic imaging of surfaces relies on the measurement of small changes (< 10{sup -9} m) in the bending of microcantilevers. Changes in the conduction band charge carrier density can result either from direct photo-generation of free charge carriers (electrons, holes) or from photoelectrons emitted from thin metal film surfaces in contact with a semiconductor microstructure which forms a Schottky barrier. In their studies, they investigated three systems: (1) Si microstructures, (2)InSb microstructures and (3) Si microstructures coated with a thin film of Pt. They found that for Si the photo-induced stress results in a contraction of the crystal lattice due to the presence of excess electron-hole-pairs while for InSb photo-induced stress causes the crystal lattice to expand. They present their results and discuss their findings