Variation of electric shielding on virtual Frisch-grid detectors

Because of the low mobility of holes, CdZnTe (CZT) detectors operate as electron-transport-only type devices whose particular geometrical parameters and contacts configurations are specially chosen to minimize the contribution of uncollected holes into the output signal amplitudes (induction effect). Several detector configurations have been proposed to address this problem. One of them employs a large geometrical aspect ratio, parallelepiped-shaped crystal with two planar contacts on the top and bottom surfaces (anode and cathode) and an additional shielding electrode placed on a crystal’s side to create the virtual Frisch-grid effect. We studied the effect of the shielding electrode length, as well as its location, on the responses of 6×6×15 mm3 virtual Frisch-grid detectors. We found that the length of the shielding electrode placed next to the anode can be reduced to 5 mm with no adverse effects on the device performance. Meanwhile, this allows for charge loss correction by reading the cathode signals.