CdTe and CdZnTe semiconductor gamma detectors equipped with ohmic contacts

Semiconductor gamma detectors, equipped with ohmic contacts, are uniform and fast response devices that are not sensitive to hole trapping. Gamma generated charges flow within the detector bulk towards the ohmic contacts, and induce additional charge flow from the contacts towards them. The additional flow stems from the fundamental principles of Poisson and the continuity equations. Electrons flow from the negative contacts towards the holes and recombine with them, therefore, they overcome hole trapping. The ohmic contact effect transforms the detector into a single carrier device. Good quality ohmic contact detectors are achieved from a crystal grown by standard methods, that initially has too many traps, by adjustment of the Fermi level position within the forbidden band. The device design and its principle of operation are discussed.