Defect observation of AlInGaP irradiated with 30keV protons for multi-junction space solar cells

30keV proton irradiation effects on AlInGaP cells and diodes as a new top cell for high efficiency III-V multijunction (MJ) space solar cells are presented here for the first time. New defects such as two majority-carrier (hole) traps HP1 (E_v+1.57eV, N_T=3.9×10 ¹⁴cm^-3), HP2 (E_v+1.19eV, N_T=2. 6×10¹⁴cm^-3) and two minority-carrier (electron) traps EP1, EP2 (E_c-0.71eV, N_T=2.9×10 ¹⁵cm^-3) were observed in p-AlInGaP irradiated with a dose of 1×10¹²cm^-2 by DLTS measurements. In as-grown samples, the E1 trap appears in both of majority- and minority-carrier DLTS scans, and is attributed to the DX center. The change of remaining factor (Voc, Isc, FF, Pmax) in the AlInGaP cell with 30keV proton fluence is evaluated. As the proton fluence increases over 1 × 10¹⁰cm"2, the Pmax of the cell decreases rapidly due to the degradation in the fillfactor. At the proton fluence of 1×10¹⁰cm^-2, the short-circuit current rises above the initial value interestingly due to the depletion layer broadening with the majority-carrier removal, and is degraded gradually over 1×10¹⁰cm^-2. On comparing the Voc, Isc in the AlInGaP cell (0.6μm) and InGaP cell (0.6μm) with proton fluence, AllnGaP shows the higher radiation tolerance than InGaP.