Optical refractive index gradient measuring method for e.g. dynamic IGBT behaviour

摘要

The method involves using an electrically driven sample (1) in a state where the carrier concentration and temperature are such that a varying refractive index is exhibited. The sample is provided with source (12), gate (13) and drain (14) electrodes. A monochromatic, e.g. infrared, laser beam cluster (3) is generated and directed at the sample. The beam cluster deviation w.r.t. time is measured and recorded.The beam is incident along axis (18) and the deviation of beam (17) w.r.t. the axis is measured. A quadrant diode measures the beam displacement using preamplifiers, impedance converters and difference amplifiers. A digital storage oscilloscope is used to capture the difference amplifier output in the period of interest.