Annealing of irradiated epitaxial InP solar cells

Publisher Website
Google Scholar
Abstract
The annealing behavior of electron, proton, and alpha particle irradiated, epitaxial n+p InP solar cells has been characterized using several techniques. Current–voltage measurements were made under simulated 1 sun, AM0 solar illumination and in the dark. The radiation-induced defect spectra were monitored using deep level transient spectroscopy and the base carrier concentration profiles were determined through capacitance–voltage measurements. The irradiated cells were annealed at temperatures ranging from 300 up to 500 K. Some cells were annealed while under illumination at short circuit while others were annealed in the dark. These experiments produced essentially the same results independent of illumination and independent of the irradiating particle. An annealing stage was observed between 400 and 500 K, in which the radiation-induced defects labeled H3 and H4 were removed and the carrier concentration recovered slightly. Concurrently there was a small reduction in the junction recombination current and a slight increase in the photovoltaic (PV) output of the cell; however, most of the radiation-induced defects did not anneal, and the overall PV recovery was very small. A full analysis of the annealing data is given, and a model for the radiation response and annealing behavior of the cells is presented. The results are compared to those reported previously for irradiated, diffused junction InP solar cells. Although the radiation-induced degradation mechanisms appear to be essentially the same in the two cell types, the recovery of the PV output is found to be quite different. This difference in cell recovery is explained in terms of the defect annealing characteristics in the individual cell types.