CHARGE COLLECTION AND NOISE-ANALYSIS OF HEAVILY IRRADIATED SILICON DETECTORS

Measurements performed on high-resistivity silicon detectors irradiate d with proton and neutron flueuces, up to 3.5 x 10(14) p/cm(2), and 4. 0 x 10(15) n/cm(2) respectively, are presented. The charge collection efficiency (CCE) and the output noise of the devices have been measure d to carry out a detector performance study after irradiation. The CCE is found to slowly decrease for fluences increasing up to approximate ly 1.8 x 10(14) p/cm(2). For higher particle fluences, the device inef ficiency increases rapidly because full depletion could not be reached (up to 75% for the highest flueuce: 4 x 10(15) n/cm(2)). A complete a nalysis of the noise of the irradiated devices has been carried out as suming a simple model which correlates the main noise sources to the f luence and the leakage current. A linear dependence of the square of t he noise amplitude on the fluence has been observed: a value of the le akage current damage constant has been found to be in good agreement w ith the values reported in literature, obtained with current-voltage ( IV) analysis. An extension of the noise analysis is carried out consid ering the detectors irradiated with very high flueuces, up to 4 x 10(1 5) n/cm(2).