MECHANISM FOR THE ANOMALOUS DEGRADATION OF SI SOLAR-CELLS INDUCED BY HIGH-ENERGY PROTON IRRADIATION

High-energy and high-fluence proton irradiation of Si space solar cell s has provoked an anomalous increase in short-circuit current, followe d by its abrupt decrease and cell failure. A model is proposed which e xplains the phenomena by expressing a reduction in the carrier concent ration of the base region, in addition to a decrease of minority-carri er diffusion length. The reduction in carrier concentration due to maj ority-carrier trapping by radiation-induced defects has the effect of (1) broadening the depletion region width and (2) increasing the resis tivity of the base layer. The anomalous change in the quantum efficien cy of the cells under high-fluence (similar to 10(14) cm(-2)) irradiat ion is also explained by considering the generation of a donor-type de fect level with the irradiation.