CdZnTe semiconductor parallel strip Frisch grid radiation detectors

CdZnTe wide band gap compound semiconducting material offers promise as a room temperature operated gamma ray spectrometer. Position-dependent free charge carrier losses during transport can prevent efficient charge carrier extraction from semiconductor detectors and severely reduce energy resolution. Hole trapping losses in CdZnTe radiation detectors are far worse than electron trapping losses and resolution degradation in CdZnTe detectors results primarily from severe hole trapping during transport. Coplanar radiation detectors improve energy resolution by sensing the induced charge primarily from the motion of electrons. Demonstrated is an alternative approach to single free charge carrier sensing, in which a parallel strip Frisch grid is fabricated on either side of a parallelepiped block. The detectors are three terminal devices, but require only one preamplifier for the output signal. The prototype devices demonstrate a considerable increase in energy resolution when operated in the true Frisch grid mode rather than the planar mode, with a demonstrated room temperature energy resolution for 662 keV gamma rays of 5.91% at FWHM for a 10 mm/spl times/2 mm/spl times/10 mm device. Presently, high surface leakage currents prevent large voltages from being applied to the devices, which ultimately reduces their maximum achievable energy resolution. Further improvements are expected with the realization of reduced surface leakage currents.

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