Novel electrode geometry to improve performance of CdZnTe detectors

A novel electrode geometry to improve the sensitivity to single-polarity charge carriers in ionization detectors is presented. The electrode geometry is based on the same principle as Frisch grids in gas detectors. It reduces the sensitivity to one type of charge carrier, making the detector almost unipolar sensing. The effectiveness of the geometry was demonstrated with a CdZnTe crystal. Above X-ray energies of 40 keV, large improvements were achieved in the spectral sensitivity, and the spectral resolution could be increased further by applying a correction for charge trapping. The peak of 137Cs at 661 keV was not visible with a planar electrode, while its FWHM was 16.7% with the novel electrode geometry. The FWHM was 6.1% after correction for hole trapping.