Radiation damage and annealing in GaAs solar cells

Work on radiation damage and annealing of GaAs cells for space power applications is reviewed. The performance of cells before and after irradiation and after thermal annealing is correlated to the nature and density of defect centers identified using deep-level transient spectroscopy techniques. Two important deep levels are present in electron- and proton-irradiated GaAs cells (E_c -0.71 eV and E_v +0.71 eV). The data from periodic and continuous annealing experiments show that GaAs cells are more radiation resistant than silicon and that the damage can be annealed at temperatures as low as 200°C. On the basis of these data, specific annealing schedules that can greatly enhance the end-of-life efficiency of the cells for specific missions can be designed for GaAs solar panels