Cadmium-zinc-telluride, multiple-electrode detectors achieve good energy resolution with high sensitivity at room-temperature

Room-temperature semiconductor gamma-ray detectors have exhibited charge loss due to incomplete collection of hole charge, resulting in spectra with significant low-energy tailing, and good energy resolution has typically been achieved only with very small detectors. Researchers at Digirad Corporation have developed an innovative method for eliminating the effects of hole trapping in radiation detectors made from compound semiconductors, such as CdTe or CdZnTe. The technique involves placing one or more additional electrodes on or near the surface of the detector, biased for optimum charge collection at the signal electrode. The additional electrode(s) focuses signal charge to the signal-collecting electrode and shields that electrode from charge trapped in the detector volume. This results in excellent photopeak efficiency because essentially all of the absorbed photons are counted in the single spectral peak. Working devices have been manufactured in a variety of configurations including imaging arrays. The configuration of the new device and present understanding of the basic principles of operation are described.