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

30 keV 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/sub V/+1.57 eV, N/sub T/=3.9/spl times/10/sup 14/cm/sup -3/), HP2 (E/sub V/+1.19 eV, N/sub T/=2.6/spl times/10/sup 14/cm/sup -3/) and two minority-carrier (electron) traps EP1, EP2 (E/sub C/-0.71 eV, N/sub T/=2.9/spl times/10/sup 15/cm/sup -3/) were observed in p-AlInGaP irradiated with a dose of 1 /spl times/10/sup 12/cm/sup /spl times/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 (V/sub OC/, I/sub SC/, FF, P/sub max/) in the AlInGaP cell with 30 keV proton fluence is evaluated. As the proton fluence increases over 1/spl times/10/sup 10/cm/sup -2/, the Pmax of the cell decreases rapidly due to the degradation in the fill-factor. At the proton fluence of 1/spl times/10/sup 10/cm/sup -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/spl times/10/sup 10/cm/sup -2/. On comparing the V/sub OC/, I/sub SC/ in the AlInGaP cell (0.6 /spl mu/m) and InGaP cell (0.6 /spl mu/m) with proton fluence, AlInGaP shows the higher radiation tolerance than InGaP.