CDZNTE SEMICONDUCTOR PARALLEL STRIP FRISCH GRID RADIATION DETECTORS

CdZnTe wide band gap compound semiconducting material offers promise a s a room temperature operated gamma ray spectrometer. Position-depende nt free charge carrier losses during transport can prevent efficient c harge carrier extraction from semiconductor detectors and severely red uce energy resolution. Hole trapping losses in CdZnTe radiation detect ors are far worse than electron trapping losses and resolution degrada tion in CdZnTe detectors results primarily from severe hole trapping d uring transport. Coplanar radiation detectors improve energy resolutio n by sensing the induced charge primarily from the motion of electrons . Demonstrated is an alternative approach to single free charge carrie r sensing, in which a parallel strip Frisch grid is fabricated on eith er side of a parallelepiped block. The detectors are three terminal de vices, but require only one preamplifier for the output signal. The pr ototype devices demonstrate a considerable increase in energy resoluti on when operated in the true Frisch grid mode rather than the planar m ode, with a demonstrated room temperature energy resolution for 662 ke V gamma rays of 5.91% at FWHM for a 10mm x 2mm x 10mm device. Presentl y, high surface leakage currents prevent large voltages from being app lied to the devices, which ultimately reduces their maximum achievable energy resolution. Further improvements are expected with the realiza tion of reduced surface leakage currents.