Edge and corner effects on spectra of segmented CdZnTe detectors

We present a theoretical and experimental study on the effect of detector edges on the performance of coarsely segmented CdZnTe pad detectors. We performed an analytical calculation of the weighting potential of a finite-size detector and studied the induced charge profile on central, edge, and corner pads. The calculation involves a closed-form solution of the three-dimensional Laplace equation inside a rectangular detector. The edge effects are introduced via the boundary conditions at the detector edges. The results are that the spectra in edge and corner pads are inherently inferior with respect to the central pads. We compare our calculations to experimental results and show that they are both qualitatively and quantitatively consistent. We demonstrate that pad uniformity can be achieved by tuning of electron trapping and also by introducing a novel electrode configuration that generates almost uniform spectra from the entire detector.