Evaluation of hole traps in 10-MeV proton-irradiated p-type silicon from Hall-effect measurements

Using the temperature dependence of the hole concentration p(T) obtained from Hall-effect measurements, we attempt to uniquely determine the densities and energy levels of hole traps in 10-MeV proton-irradiated p-type silicon. Since the function p(T) exp(Eref/kT)/kT has a peak at the temperature corresponding to each hole trap level, the trap densities and energy levels can be determined uniquely and accurately. Here, k is the Boltzmann's constant, T is the absolute temperature and Eref is a newly introduced parameter which shifts the peak temperature of the function within the measurement temperature range. Three types of hole trap levels (about 0.09 eV, 0.13 eV and 0.19 eV above the top (EV) of the valence band) are observed, and these hole trap densities increase with increasing 10-MeV-proton fluence. The hole traps at EV+0.09eV and EV+0.19 eV have been reported and their origins have been discussed. However, the hole trap at EV+0.13 eV has not yet been reported. The quantitative relationship between the decrease in hole concentration and the increase in densities of certain traps due to proton irradiation has been clarified for the first time.