Infra-red microscopy of Cd(Zn)Te radiation detectors revealing their internal electric field structure under bias

This paper describes the use of the Pockels electro-optic effect to both visualise and measure the internal electric field present within CdZnTe detectors under normal bias conditions. Use was made of a silicon charge coupled device (CCD), as an image sensor, in conjunction with a 940 nm LED to illuminate a 3×3×5 mm detector crystal with polarised infra-red light. The experiment was arranged so that a ×40 image of the crystal showing a contour plot of electric field intensity could be generated. Further, more precise E-field measurements, were obtained using a 1.2 μm laser diode (LD) and a germanium photodiode detector. Together these experiments indicate substantially non-uniform electric fields within the detector crystals used