Material properties and room-temperature nuclear detector response of wide bandgap semiconductors

Several semiconductor materials for room-temperature X-ray and gamma-ray detectors, including HgI2, Cd1-xZnxTe (CZT), GaAs, and PbI2 have been studied at Sandia National Laboratories, California. A comparison of the spectral response of these detectors will be given and related to material properties, such as charge carrier drift length, crystal purity, structural perfection, acid material stoichiometry, as well as to the crystal growth techniques and device fabrication processes published elsewhere. Room-temperature detector spectral responses for each of these materials are presented, for photon energies in the range of 5.9 to 662 keV. CZT and HgI2 detectors demonstrate excellent energy resolution over the entire energy range, while PbI2 detectors exhibit reasonable response only up to about 30 keV. Some of the semi-insulating GaAs detectors fabricated from vertical gradient freeze materials show good spectral resolution for lower energies up to similar to 60 keV, whereas other SI-GaAs detectors studied at Sandia function only as counters. Finally, some predictions on the future materials development of these wide bandgap semiconductors for room-temperature radiation detector applications will be discussed.