Charge collection efficiency degradation on Si diodes irradiated with high energy protons

The charge collection efficiency (CCE) of several p-type Si diodes has been determined by the Ion Beam Induced Charge (IBIC) technique with 4 MeV protons. In addition, the time evolution of the collected carriers has been recorded as a function of the reverse bias voltage. The diodes were irradiated in our cyclotron with 17 MeV protons and fluences ranging from 3.3 × 1011 to 1.65 × 1013 p/cm2. The high energy irradiation was selected because of the practically constant value of the proton stopping power across the samples, leading to a uniform vacancy profile with depth. It is observed that the CEE decreases linearly with radiation fluence while the leakage current increases with ion dose. From these results, the diffusion length of minority carriers, the damage constant and the damage coefficient of p-type Si diodes have been evaluated.