The effect of base dopant level and thickness on the radiation response of Ga0.47In0.53As solar cells

The dependence of the radiation response of Ga_0.47In _0.53As solar cells on the thickness of the cell base was investigated. The major conclusion of the Ga_0.47In_0.53 As radiation testing done to date is that the degradation of open circuit voltage (V_∝) is the controlling factor. This seems to be due to the low base dopant level of the cells which have been studied, and the suggestion is that an increase in the dopant level will decrease the sensitivity of V_∝. However, an increase in the dopant level may increase the sensitivity of the short circuit current density (J_sc) to irradiation, so in contrast to V_∝, a cell with a radiation hard J_sc is lightly doped and thin. Nevertheless, previous results have shown that a 5μm thick Ga_0.47In_0.53As base doped to 2 × 10¹⁶ cm^-3 shows significantly more resistance in V_∝ than observed presently with no change in the sensitivity of J_sc. Thus, the optimum design for a radiation hard Ga_0.47In_0.53As solar cell seems to be a 3-4μm thick base with a dopant concentration of > 2 × 10¹⁶ cm^-3