Laser Induced Transient Current Pulse Shape Formation in (CdZn)Te Detectors

Abstract

The transient-current technique belongs to those methods routinely used for the determination of the characteristics of semiconductor radiation detectors. In this paper we study laser-induced transient current waveforms (CWFs) measured on planar CdZnTe detector down to applied electric field 170 V/cm. We analyze how the passing of the signal through the real electronic circuit influences the appearance of CWF. Detector equivalent circuit and evidence of the parasitic induction component in the CWF shape are demonstrated. Transfer function of the electronic setup is measured and employed to retrieve the original CWF shape by using different mathematical deconvolution procedures. The pulse shape restoration results in an amendment of evaluated space charge density by up to 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for CWFs shorter than 20 ns. Both restored CWFs and transient charge waveforms are used in the charge collection efficiency calculation and fitted with standard Hecht equation.