Future Trends in Microelectronics: From Nanophotonics to Sensors to Energy

Three-Dimensional Position-Sensitive Wide Bandgap Semiconductor Gamma-Ray Imaging Detectors

Zhong He

Nuclear Engineering and Radiological Sciences Department The University of Michigan, Ann Arbor, MI 48109-2104, U.S.A.

1.   Introduction

Among the three major types of gamma-ray detectors – based on scintillators, gases or semiconductors – semiconductor detectors can offer the best energy resolution as well as the high detection efficiency of a solid state detector. High-purity germanium (HPGe) detectors have been the gold standard for high-resolution gamma-ray spectroscopy since the mid 1970’s,¹ but they must be operated at cryogenic temperatures of around 77 K (about –196 °C) due to germanium’s small bandgap of ~0.7 eV. The requirement of cryogenic cooling has made the deployment of HPGe detectors difficult for many applications. Although mechanically cooled HPGe detectors have become available in recent years, there has been strong interest in finding alternative detector technologies to minimize power consumption, instrument weight and risks associated with failures of cooling and vacuum systems of HPGe detectors.

Wide bandgap semiconductors with high atomic numbers and densities are desired for both efficient gamma-ray detection and the convenience of room-temperature operation. Several wide bandgap semiconductors, such as CdTe, CdZnTe, Hgl₂ and TIBr have attracted the most attention. However, charge-carrier trapping within the detector material, in particular the trapping of ...