Modeling of deep traps in diamond detectors by means of β particles-induced conductivity measurements

A quantitative model of radiation-induced carrier transient conductivity has been used to explain the influence of very high neutron irradiation (up to 21015 cm2 1MeV equivalent) on the trappingand recombination mechanisms of Chemical Vapor Deposited polycrystalline diamond devices, prepared for particle tracking. The model fits very well room temperature measurements of radiation-induced conductivity at different levels of thermal de-trapping, i.e. with different amounts of charged deep traps. The analysis in this paper depicts three types of traps, close to the band-edge, characterized by different values of capture cross-sections, and a broad recombination center. The traps form a continuous distribution, with a constant density of states per unit energy in the investigated energy range (0.2 eV). The density of states is determined from the current behavior vs. thermal de-trappingtime. The structure of the deep recombination centers is unaffected by neutron irradiation. On the other hand, the concentration values of the traps with lower cross-sections increase after irradiation. A saturation effect is observed which has been previously reported [M. Bruzzi et al., Diamond Relat. Mater. 10 (2001) 601] by use of Thermally Stimulated Current spectroscopy (TSC).