Pulse-shape analysis in Cd0.9Zn0.1Te0.98Se0.02 room-temperature radiation detectors

Abstract

The effect of trapping of charge carriers on the shape of the charge pulses from room temperature nuclear detectors, based on a recently discovered quaternary semiconductor Cd0.9Zn0.1Te0.98Se0.02 (CZTS), has been studied. We present a charge-trapping model that explains the pulse shapes for its entire duration from radiation detectors containing multiple defect types. A piecewise continuous model, based on the movement of a large number of charge carriers rather than a single charge, has been proposed to explain the pulse shapes from planar room temperature nuclear detectors. An experimental method based on the model has been described to extract charge-trapping information. This model can be applied to similar semiconductor detectors with electrically active trap centers, in general, to extract information like pre-trapping drift times. Charge pulses from a CZTS planar detector, exposed to 5486 keV alpha particles emitted by a 241Am source, were acquired using a digitizer, and the pulse shapes were explained based on the proposed model. The pre-trapping drift times for electrons as well as holes in CZTS were calculated and studied as a function of operating bias voltage, and a contrast between their bias dependent behaviors was noticed, indicating the behavioral difference of electron and hole traps.