The generation lifetime damage factor and its variance in silicon

The generation damage factor and its variance for silicon are determined for proton energies of 12, 22, and 63 MeV, and for fission neutrons. Measurement of the variance is made for the first time using 61504 pixels of a charge-injection device. The variance is an intrinsic characteristic of damage due in part to differences in numbers and magnitudes of atomic recoils produced in each pixel. Calculations of the variance due to the recoil spectrum show that the magnitude of the relative variance is determined by Coulombic recoils. In fact, the experimental relative variance is almost two orders of magnitude less for fission-neutron-induced dark current increases than for the proton case. The relative variance was found to decrease as the proton energy was increased. The calculation shows that this trend is caused by the inelastic contribution to the relative variance of the recoil spectrum.>