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 2×1015 cm−2 1 MeV equivalent) on the trapping and 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-trapping time. 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).