Effects of charge sharing in 3-D position sensitive CdZnTe gamma-ray spectrometers

Two 3-D position-sensitive semiconductor γ-ray spectrometers operable at room temperature, have been fabricated using 1 cm3 cubic CdZnTe crystals. γ-Ray spectra have been obtained from 11(x)×11(y)×20(z) voxels, each corresponding to ∼0.7×0.7×0.5 mm in the detector volume. Individual spectra from each of the 2420 voxels were corrected for electron trapping, differences in weighting potentials, and the gain variation of the readout circuitry. Energy resolutions of 1.70% (11.3 keV) FWHM and 1.84% (12.2 keV) FWHM were obtained at 662 keV from the combined output of the entire volume for single-pixel events. Charge sharing between neighboring pixels has been observed and the sizes of electron clouds are estimated from these experimental data. An understanding of electron cloud dimensions is important for the design of future detectors using pixellated electrodes.