Fundamental understanding of radiation-induced defects in n+ p InGaP solar cells

We have carried out detailed thermal annealing investigation of radiation-induced defects in p-InGaP and solar cells after irradiation with 1 MeV electrons and have observed subsequent recovery of the solar cell properties. Correlation with changes in the deep level transient spectroscopy spectra observed in irradiated and annealed n⁺/p InGaP diodes and solar cells shows that the H2 (E_V+0.5D-0.55eV) and H3 (E_V+0.76 eV) defects have a dominant role in governing the minority-carrier lifetime as well as carrier removal. In addition, the concentration of the H2 defect is found to decay significantly as a result of room temperature storage for 40 days, suggesting that InGaP based solar cells will display superior radiation tolerance of InGaP based solar cells in space. Finally, the deep donor like-defect H2 is tentatively identified as phosphorus Frenkel pair.