Noise in CdZnTe detectors

Noise in CdZnTe devices with different electrode configurations was investi gated. Measurements on devices with guard-ring electrode structures showed that surface leakage current does not produce any significant noise. The pa rallel white noise component of the devices appeared to be generated by the bulk current alone, even though the surface current was substantially high er. This implies that reducing the surface leakage current of a CdZnTe dete ctor may not necessarily result in a significant improvement in noise perfo rmance. The noise generated by the bulk current is also observed to be belo w full shot noise. This partial suppression of shot noise may be the result of Coulomb interaction between carriers or carrier trapping. Devices with coplanar strip electrodes were observed to produce a 1/f noise term at the preamplifier output. Higher levels of this 1/f noise were observed with dec reasing gap widths between electrodes. The level of this 1/f noise appeared to be independent of bias voltage and leakage current but was substantiall y reduced after certain surface treatments.