Proton radiation hardness of GaInAsP alloys for space solar cell applications

Abstract

AbstractRecent technology development in space mission design has raised a demand for space solar cells with a higher level of radiation tolerance as compared with state‐of‐the‐art, commercially available products. Therefore, new material systems are being investigated. Recently, we highlighted the superior radiation tolerance of GaInAsP solar cells to 1 MeV electron irradiation as compared with standard GaAs solar cells. A high InP fraction within this semiconductor compound was found to foster the regeneration rate of electron‐induced defects when the solar cells were annealed at 60°C under AM0 illumination, which are typical space‐operating conditions. In light of considering this material system in future radiation‐hard designs, the degradation of GaInAsP solar cells subjected to proton irradiation also needs to be investigated. Here, we report on the degradation and regeneration of GaInAsP solar cells lattice‐matched to InP substrates after 1 MeV proton irradiation. A detailed description of the radiation damage is achieved by solar cell numerical modeling combined with deep‐level transient spectroscopy analysis. The irradiation‐induced defects are quantified, and their evolution during annealing is monitored. The results are compared with the degradation data of similar solar cells obtained after 1 MeV electron irradiation. A slower regeneration rate of the proton‐induced defects is found in comparison with the electron‐induced defects. This difference is ultimately attributed to a different topology of the radiation damage caused by proton irradiation.