Analysis of radiation damage to Si solar cells under high-fluence electron irradiation

Radiation testing of Si n+-p-p+ space solar cells has revealed an anomalous increase in short-circuit current Isc, followed by an abrupt decrease and cell failure, induced by high-fluence (>1016 cm-2) electron irradiation. A model which can be used to explain these phenomena by expressing the change in majority-carrier concentration p of the base region as a function of the electron fluence has been proposed in addition to the well-known model in which Isc is decreased due to minority-carrier lifetime reduction with irradiation. The reduction in p due to majority-carrier trapping by radiation-induced defects has two effects; one is broadening of the depletion layer which contributes to the increase in the generated photocurrent and that in the recombination-generation current in the depletion layer, and the second is an increase in the resistivity of the base layer resulting in an abrupt decrease of Isc and failure of the solar cells. (author)