Energy-Dependent Proton Damage in Silicon

Non Ionizing Energy Loss (NIEL) in the sensor bulk is a limiting factor for the lifetime of silicon detectors. In this work, the proton-energy dependent bulk-damage is studied in n- and p-type silicon pad diodes. The samples are thin (200 μm thick), and oxygen enriched (bulk material types: MCz, standard or deep-diffused FZ). Irradiations are performed with 23 MeV, 188 MeV and 23 GeV protons; the 1 MeV neutron equivalent fluence assumes selected values in the range [0.1, 3]·10$^{14}$cm$^{−2}$. In reverse bias, Current-Voltage (IV) and Capacitance-Voltage (CV) measurements are performed to electrically characterise the samples; in forward bias, IV and CV measurements point out the transition from lifetime to relaxation-like semiconductor after irradiation. By means of Thermally Stimulated Current (TSC) measurements, 13 bulk defects have been found after proton irradiation. Firstly, TSC spectra are analysed to obtain defect concentrations after defect filling at the conventional temperature T$_{fill}$ = 10 K. Secondly, temperature dependent capture coefficients of bulk defects are explained, accordi (T$_{fill}$ < 130 K). Thirdly, a new method based on the SRH statistics and accounting for cluster-induced shift in activation energy is proposed; it allows to fully characterise bulk defects (in terms of activation energy, concentration and majority capture cross-section) and to distinguish between point- and cluster-like defects. A correlation is noted between the leakage current and the concentration of three deep defects (namely the V$_2$, V$_3$ and H(220K) defects), for all the investigated bulk materials and types, and after all the considered proton energies and fluences. At least five defects are found to be responsible for the space charge, with positive contributions from the E(30K) and B$_i$O$_i$ defects, or negative contributions from three deep acceptors H(116K), H(140K) and H(152K)