Thermal annealing of radiation-induced defect centers during recovery of diffused junction and epitaxial InP solar cells

The annealing properties of irradiated diffused junction (DJ) and epitaxial (epi) n⁺p InP solar cells is presented. The cells are characterized through 1 sun, AM0 I-V measurements and deep level transient spectroscopy (DLTS). The DJ cells were annealed up to 500 K, and the epi cells were annealed up to 650 K. Annealing was performed under illumination and in the dark. After irradiation, essentially the same defect spectra were measured in both cell types, and the spectra matched that reported in the literature. The annealing stages of the photovoltaic (PV) parameters are correlated with observed defect reactions. The DJ cells are seen to recover completely due to the removal of almost all of the defect levels. The epi cells, however, showed only partial recovery due to limited defect annealing. In both cases, the H5 defect and the electron trapping centers are seen to strongly affect the cell output. These results help to explain the annealing behavior in the two cell types