Optical beam-induced currents

Optical Beam-Induced Current (OBIC) is a semiconductor analysis technique that employs a scanning laser beam to induce a current flow within a semiconductor sample which may be collected and analyzed to generate images that represent the sample's properties. It is a useful imaging technique for detecting or locating various defects or anomalies on a semiconductor sample. Conventional OBIC scans an ultrafast laser beam over the surface of the sample, exciting some electrons into the conduction band through what is known as 'single-photon absorption'. As its name implies, single-photon absorption involves just a single photon to excite the electron into conduction. This can only occur if that single photon carries enough energy to overcome the band gap of the semiconductor (1.2 eV for Si) and provide the electron with enough energy to make it jump into the conduction band.