Semiconductor Scintillator for Three-Dimensional Array of Radiation Detectors
Dept. of Electrical and Computer Engineering, SUNY-Stony Brook Stony Brook, NY 11794-2350, U.S.A.
There are two large groups of solid-state radiation detectors that dominate the area of ionizing radiation measurements: scintillation detectors and semiconductor diodes. The scintillators detect high-energy radiation through generation of light, which is subsequently registered by a photodetector that converts light into an electrical signal. Semiconductor diodes employ reverse biased pn junctions where the absorbed radiation creates electrons and holes, which are separated by the junction field thereby producing a direct electrical response. Both groups of detectors are extensively reviewed in the classical treatise by Knoll.1
Most scintillators reported in the literature are implemented in wide-gap insulating materials doped (“activated”) with radiation centers. A classic example of a solid-state scintillator is sodium iodide activated with thallium (NaI:Tl), introduced by Hofstadter2 more than 60 years ago.
The typical band diagram of a solid-state scintillator is shown in Fig. 1. Because of the much longer wavelength of the scintillation associated with the activator energy levels – compared to the interband absorption threshold – the insulating scintillators are very transparent to their own luminescence. However, this advantage comes at a price in the ...