Effect of electron irradiation dose on the performance of avalanche photodiode electron detectors

Avalanche photodiodes (APDs) are efficient detectors for electrons with energies below 100 keV. The damaging effects of 8 keV electron beam irradiation on the dark current and the output signal of the APD detector were investigated in this study. The APD dark current increases after electron doses exceeding 1.4 x 1013 cm(-2). Preirradiation by high doses of 8 keV electrons further causes a deformation of the pulse height distribution of the APD output in the subsequent detection of low-flux electrons. This effect is particularly prominent when the energy of the detected electrons is lower than that of the damaging electrons. By comparing the experimental data with results of a simulation based on an electron trapping model, we conclude that the degradation of the APD performance is attributable to an enhancement of secondary-electron trapping at irradiation induced defects. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3056053]