Electron and proton damage coefficients for heteroepitaxial InP solar cells

Indium phosphide solar cells are known to be significantly more radiation resistant than either gallium arsenide or silicon. Their growth by heteroepitaxy offers additional advantages over growth by homoepitaxy. InP cells have been grown on lower cost substrates and if heteroepitaxial cells are to be used in space power applications, their behavior under electron and proton irradiations has to be understood. This work presents the new calculated results for 1 MeV electron and 0.2 to 10 MeV proton irradiations on the performance of the n⁺p heteroepitaxial InP cells. The heteroepitaxial InP solar cell efficiency degradation has been explained by the decrease in the base diffusion length. The effect of carrier removal has been considered in the calculations. The electron and proton diffusion length damage coefficient K_L has been calculated as a function of fluence. The proton damage coefficient remains almost constant with fluence for 0.5, 3, and 10 MeV energies, but increases for the 0.2 MeV. The 1 MeV electron damage coefficient decreases with fluence. These results suggest that the electron and proton damage mechanisms are different