engleski

Defects induced by irradiation with fast neutrons in n-type germanium

Electrically active defects induced in n-type Sb-doped Ge crystals by irradiation with fast neutrons have been studied by means of conventional deep level transient spectroscopy (DLTS). The neutron-irradiation-induced DLTS spectra are compared with those recorded after irradiations with 4MeV electrons. The evolution of the neutron- and electronradiation- induced defects upon 30-min isochronal annealing in the temperature range 100– 300 1C has been investigated. Although the DLTS spectra from electron- and neutron-irradiated materials show some similarities and there are also signifi cant differences. The neutron irradiation resulted in the appearance of a number of peaks related to electron and hole deep level traps in the DLTS spectra. In the upper half of the gap at least six electron traps were observed with the following activation energies for electron emission (En): 0.08, 0.12, 0.17, 0.22, 0.29 and 0.34 eV. Some of these traps were detected in the electron-irradiated samples. Particularly the trap with En ¼ ; 0.34 eV was the dominant one after electron irradiation and was identifi ed as the second acceptor level of the Sb– vacancy pair. In Ge:Sb samples irradiated with high fl uences of neutrons the trap with En ¼ ; 0.29 eV [E(0.29)] was the dominant electron trap. It is argued that the E(0.29) trap is related mainly to the second acceptor level of Ge divacancy (V2). It is suggested that upon annealing of neutronirradiated samples at temperatures higher than 100 1C mobile divacancies and Sb– V pairs can interact with Sb atoms with the formation of Sb– V2 and Sb2– V complexes, which have acceptor levels in the lower half of the gap.

irradiation ; n-type germanium

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