Recombination centers in electron irradiated Si and GaAs.

Using the current-voltage characteristics of an abrupt Si n(+)p junction, we show how the minority carrier lifetime, the capture cross sections for electrons and holes, and the energy level of the corresponding recombination center can be determined independently, thus allowing to characterize completely this center. This technique is illustrated by studying the main recombination center in p-type Czochralski grown Si and epitaxial n-type doped GaAs layers. It is then applied to characterize the recombination centers introduced by electron irradiation at various temperatures in Si and GaAs solar cells. In electron irradiated Si cells, we find that the main recombination center introduced by irradiation at 90 K is the vacancy. It becomes the divacancy for higher irradiation temperatures. In irradiated GaAs the recombination center, presumably associated with the As vacancy, does not change with the temperature of irradiation in the range 80 - 300 K.