Frequency dependence of AC conductance of non-irradiated and neutron irradiated silicon detectors.

The admittance-Y (real and imaginary) as a function of frequency (omega) and temperature (T) of silicon detectors, non-irradiated and neutron irradiated, were studied An electric circuit model of Y(omega) was calculated. The experimentally measured data for real part of admittance G as a function of omega have shown a quadratic dependence G similar to omega(2), for temperatures T greater than or equal to 40K. This experimental dependence was the same as resulted from the calculations based on the electric circuit model for the region of values T where G was proportional to the resistivity of the silicon detector (rho). For temperatures T<40K, the A.C. conductance G similar to omega(a) (n<2). It was shown that the value of omega, where this dependence appears, decreases with decreasing T. Due tot he increase of mobility of free carriers at low temperatures where G similar to rho (50 less than or equal to T less than or equal to 270K), the value of G decreased with decreasing T ( G similar to T-a, a 2.3 for 170 less than or equal to T less than or equal to 270 K and a=1.8 for 50 less than or equal to T less than or equal to 150K). At T less than or equal to 20K due to the process of freeze-out of free carriers, the value G remains practically independent on omega and on further decrease of T. Measurements on neutron irradiated samples at Phi > 10(13) n/cm(2), have shown important changes in the dependence of G as a function of omega and T.