Noise reduction in CdZnTe coplanar-grid detectors

Abstract

Noise measurements on CdZnTe detectors show that the main sources of detector-related noise are shot noise due to bulk leakage current and 1/f noise due to the detector surfaces. The magnitude of surface leakage current appears to have little or no effect on the detector noise. Measurements on guard-ring devices fabricated using gold-evaporated contacts show that the contacts behave as Schottky barriers, and the bulk current at typical operating voltages is likely dependent on the contact properties rather than directly on the material's bulk resistivity. This also suggests that the level of shot noise is affected by the detector contacts and not necessarily by the material's bulk resistivity. A significant reduction in the noise of coplanar-grid detectors has been obtained using a modified contact fabrication process.