Neutron-induced defects in high-purity germanium

Abstract

Fast neutron-induced defects have been studied in high-purity n- and p-type germanium using capacitance techniques. Capacitance versus voltage has been applied to monitor the total defect introduction rate. The defects introduced by low-temperature (10 K) and room-temperature irradiations, as well as the native defects present in the As-grown materials, are characterized by deep level transient spectroscopy. The restrictions of these techniques when applied to a material having a low-free-carrier concentration are pointed out. The previous knowledge of the annealing behavior and introduction rates of defects created by electron irradiation allowed some information about the microscopic origin of the point defects observed to be obtained. The dominant defects induced by the irradiation are vacancy or divacancy related. The study of the stable traps at low temperature provides a reasonable understanding of the primary defects and their annealing behavior up to room temperature. The characteristics of the secondary defects created after low-temperature irradiation and annealing are compared with those created directly by room-temperature irradiation. The origin of the Ev+0.07 eV level present in dislocation-free high-purity germanium is also discussed.