Radiation hard, double-graded, drift-dominated InP solar cells

Double-graded and drift-dominated InP solar cells have been designed, fabricated and characterized. By grading the doping concentration in both the emitter and the base of the InP solar cell, we create an electric field through the active layer, and thus efficiently collect carriers by drift which results in higher than 80% overall internal quantum efficiency. By adding an InP P/sup ++/ delta doped layer, we eliminate the depletion region between the substrate and the epitaxial layers, thereby reducing the series resistance and improving cell quality. The power remaining factor after 10/sup 15/ electrons/cm/sup 2/ 1 MeV electron irradiation is 93.7%. The results indicate that our design promises to result in a gravimetrically efficient and radiation hard space solar cell.