DIRECT OBSERVATION AND MEASUREMENTS OF NEUTRON-INDUCED DEEP LEVELS RESPONSIBLE FOR N-EFF CHANGES IN HIGH-RESISTIVITY SILICON DETECTORS USING TCT

Neutron-irradiation-induced deep levels responsible for changes of the space charge concentration N-eff in high-resistivity silicon detector s have been revealed directly using the Transient Current Technique (T CT). It has been observed by TCT that the absolute value and sign of N -eff experience changes due to the trapping of non-equilibrium free ca rriers generated near the surface (about 5 mu m depth into the silicon ) by short wavelength laser pulses in fully depleted detectors. Electr on trapping causes N-eff to change towards negative direction (dr more acceptor-like space charges) and hole trapping causes N-eff to change towards positive direction (or more donor-like space charges). The sp ecific temperatures associated with these N-eff changes are the freeze -out temperatures for free carrier emission from the corresponding dee p levels. The carrier capture cross sections of various deep levels ha ve been measured directly using TCT with different free carrier inject ion schemes.