Radiation effects in Ga0.47In0.53As devices

The effects of irradiating Ga_0.47In_0.53As solar cells and p-i-n photodiodes with 1-MeV electrons were measured using deep level transient spectroscopy (DLTS) and both dark and illuminated (1 sun, air mass zero (AM0)) I-V measurements. Fits of the dark I-V data to the two-term diode equation before irradiation were satisfactory, yielding an estimated bandgap energy of 0.79 eV. The DLTS detected two radiation-induced defect levels, one shallow (0.10 eV) and one near mid-gap (0.29 eV). Temperature coefficients of the Ga_0.47In _0.53As photovoltaic parameters follow the same general behavior as for other solar cell materials (e.g., Si and GaAs). However, a sharp decrease in the short circuit current is observed above ≈375 K. This temperature is reduced by irradiation. Isochronal thermal annealing induced recovery in the photovoltaic parameters at ≈400 K, coinciding with an annealing stage of the near mid-gap defect level