Over the last decade, CdZnTe (CZT) has become the most promising material for hard X-ray detectors, and now its application ranges from medical industry, home land security to astronomy. In astronomy, the Burst Alert Telescope (BAT) at Swift, launched at Nov 2004, is the first space mission employing a large array (0.5 m²) of CdZnTe detectors. An ESA mission, INTEGRAL, also uses an array of CdTe detectors, which are a close cousin of CdZnTe detector.

CdZnTe detector becomes popular in hard X-ray astronomy for multiple reasons. Its high atomic number elements efficiently stop X-rays at reasonable thickness. Many metallization techniques such as pixellization and coplanar grid have been developed to provide good energy resolution (~1-2 keV), substantially superior to that of conventional scintillators and even approaching Ge spectrometers for some applications. In particular, pixellization allows excellent positional sensitivity, which is essential for many imaging applications. Operability at room temperature also makes CdZnTe detector very attractive.

Despite all the progress of CdZnTe development in the past, the detector technology required for ProtoEXIST and EXIST is very challenging due to their ambitious scientific goals. Our efforts at CfA along with our collaborators focus on developing CdZnTe detectors necessary for the future generation of wide-field hard X-ray survey telescopes.