The study of irradiated nuclear detectors based on silicon epitaxial layers

The dE/dx nuclear detectors based on epitaxial silicon layer were studied after irradiation with 7 MeV electron beam using the Alpha Particle Sensitivity (APS) method.This technique may represent an attractive method to evaluate the modifications of charge collection characteristics of a specific irradiated surface layer. The alpha particles are used as an electric charge generator at different depths in the sample. The average penetration depth can be adjusted in the range 0 - 25 μm using a variable distance between the 241 Am alpha source and the detector. The reflecting interface between the epitaxial layer and the Si substrate (n/n+) offers the possibility to evaluate not only the electric charge generated in the depleted layer of the p+/n junction but also those carriers collected by diffusion from the neutral region. The presence of the two peaks in the spectrum was used to measure the depth of the space charge region of the unbiased junction and in the same time the behaviour of charge collection efficiency versus the irradiation dose. (Author)