Evolution of defect complexes in silicon single crystals with heavy fluence 10 MeV proton irradiation

We have investigated the defect structure of 10 MeV proton irradiated Czochralski-grown Si single crystals and space solar cells with boron-doped p-Si base layer using deep level transient spectroscopy measurements to characterize both vacancy interstitials and their complex-type defects and to monitor their evolution upon annealing at temperatures $\text{⩽500\hspace{0.05em}°}\mathrm{C}.$ We have observed quite different annealing behavior of the deep levels for conduction-type converted samples (n-type) irradiated at ${\text{1×10}}^{14}$ ${\mathrm{p/cm}}^{\mathrm{2}}$ as compared to an intermediate dose of ${\text{3×10}}^{13}$ ${\mathrm{p/cm}}^{\mathrm{2}}.$ The observed concentrations of the minority carrier level at $E_C\text{−0.20}$ eV and the new electron level at $E_C\text{−0.71}$ eV that can be seen in type converted samples, have been found to be enough to account for the carrier removal effects. The present study also throws light on the fact that heavy proton irradiation not only changes the structure of the device (from p to n type) but also makes the defect structure complex as compared to the simple defect structure in low dose samples. Isochronal thermal annealing after heavy irradiation provides interesting insight into defect interactions. In particular, the new observed prominent electron level ${\mathrm{(E}}_C\text{−0.71}$ eV) in type converted cells exhibits a mutual thermal transformation with hole level ${\mathrm{(E}}_V\text{+0.36}$ eV) upon annealing.