Application of the barrier method to semiconductor spectrometers for nuclear radiation

High purity semiconductor crystals with low thermal genneration rate such as Si and Ge at 77 K have been operated as radiation spectrometer when sandwiched between two thin insulating barrier layers without any preparation besides etching. The working time of such devices is determined by the ratio of the charge on the capacitor formed by the semiconductor surface, the insulating layers and the metal contacts, to the total charge generation rate in the semiconductor volume (thermal generation and absorption of ionizing radiation). Typical working times of 10 h for Si and 1 h for Ge have been obtained with gamma energy resolution comparable to junction detectors. Periodical recharging of the detectors can be performed with light flashes in very short time so that the dead time of a spectrometer incorporating junctionless crystals is negligible. Operation without the presence of an external electric field is possible due to insulator interface charge trapping and was also performed, showing some advantages.