CfA EXIST Web Site

CfA EXIST Web Site CZT Detector Development

Cadmium Zinc Telluride (CZT) is a high Z, large bandgap, semiconductor which shows excellent promise as a hard X-ray detector. The material has good electron transport properties, and the spectroscopic performance surpasses that of regular scintillators. By adding othogonal strip electrodes on two faces, or an array of pixel electrodes on one face, a single wafer can be segmented into a position sensitive detector for use in an imaging telescope.

At Harvard-Smithsonian Center for Astrophysics, we are developing pixellated CZT detectors for our next balloon-borne coded aperture telescope, EXITE3, and possibly for EXIST. We are currently optimizing the pixel electrode dimensions, and studying to see whether the addition of steering electrodes around the pixels improves charge collection.

We are also studying the effectiveness of blocking contacts on CZT. By creating a P-I-N contacts on CZT, we can reduce the amount of leakage current and improve the spectroscopic resolution.

We carried a small CZT experiment on the last EXITE2 science flight in Spring of 1997. The experiment was designed to record the background spectrum in the CZT, in a configuration similar to what would be expected in a large field-of-view telescope. On our next EXITE2 flight, we will carry two tiled 16 pixel detectors which will be read out by a single 32 channel preamplifier ASIC.