ABSTRACT
This chapter discusses the high-resolution cadmium telluride (CdTe) diode detectors and their application to gamma-ray imaging. To use CdTe and cadmium zinc telluride (CdZnTe) for detecting gamma-rays with energy higher than a few hundred kiloelectron volts, the bias voltage necessary to eliminate the low-energy tail at a level to achieve resolution of a few kiloelectron volts must be higher than a few hundred volts. The technique for growing a large single CdTe crystal with good charge transport properties has been established by the traveling heater method (THM). The CdTe diode detectors shows degradation of the spectral properties over time following exposure to high bias voltage, similarly to the so-called polarization phenomenon in semiconductor devices. CdTe devices begin to appear in the field of medical imaging. One interesting application is a semiconductor PET using CdTe detectors. The high-energy resolution of CdTe could provide a narrow energy window for coincidence measurement leading to a high signal-to-noise ratio.
