Exploration of single-event effects under defocused laser irradiation: Analysis of charge collection in bipolar devices

Pulsed lasers are employed to simulate Single Event Effects (SEEs) on Earth, with their feasibility empirically validated. In practical applications, it is necessary to correlate laser test results with high-energy particle measurements to accurately predict spatial SEE rates. Most of the current methods rely on charge collection RPP models or nested RPP models for laser-energy particle correlation. These models have not yet accounted for the effect of ionization trace differences. In this paper, ionization traces with different radial dimensions are obtained at different depths inside a bipolar device operational amplifier LM324 by adjusting the defocusing amount of the laser. This study compares charge collection generated by the laser with different characteristic ionization traces and analyzes experimental error factors and the charge collection mechanism. The results indicate that the radial size of the ionization traces inside the device is the main factor affecting the charge collection. Larger radial size of ionization traces on the surface area of the device results in greater charge collection, while smaller radial size of ionization traces in the depletion area and the substrate layer leads to increased charge collection. Additionally, efforts should be made to minimize the effects of movement accuracy errors and off-axis angle errors on the quantitative characterization of the test.