Temporal changes of output signals from CdTe radiation detector measured by optical laser pulses

To investigate temporal change of the output signal from the CdTe detectors, optical laser pulses was used for carrier generation. Electrical responses from the CdTe detectors were detected as a function of generated carrier density and applied bias voltage. Temporal change of the internal electric field at defined position in the CdTe detector can be directly observed by the laser pulse measurements. Laser pulses were irradiated to the center of the cleaved side surface of the CdTe detectors. Time traces of output voltage amplified by charge-sensitive preamplifier were measured by oscilloscope as a function of time after applying bias voltage. The pulse height was decreased and the rise-up time was increased as a function of the time. Rate of these changes were increase with decreasing the applied bias voltage and with increasing incident laser power, which corresponds to carrier density generated in the detector. It is concerned that the distribution of the depletion layer are modified and the electric field at the center of the detector are decreased with the time under bias voltage by the polarization phenomena.