Using variable threshold displacement energy for degradation fitting of particle irradiated multi-junction space solar cells

The degradation of Ga
_0.5
In
_0.5
P/GaAs/Ge triple junction 3G28, 3G30 and isotype 3G28 Ga
_0.5
In
_0.5
P and GaAs cells is analysed and the characteristic degradation curves are determined. The well established displacement damage method was applied in combination with a variable T
_d
as a fitting parameter. The validity of the NIEL data analysis was verified by the reproduction of a T
_d
of 21 eV for GaAs. The same method that has been published recently yields 36 eV for Ga
_0.5
In
_0.5
P single junction cells. The analytically calculated NIEL for GaAs and Ga
_0.5
In
_0.5
P with these respective threshold displacement energies overlap, which is the reason why both NIELs can be used for degradation fitting of the triple junction cell.