The radiation response of heteroepitaxial p+n InP/Si solar cells

The 1 MeV electron irradiation-induced degradation of both heteroepitaxial and homoepitaxial p/n InP solar cells grown by MOCVD is presented. The heteroepitaxial cells were grown on Si substrates (InP/Si). The cells were characterized through current-voltage (IV) and deep level transient spectroscopy (DLTS) measurements. After irradiation, essentially the same electron trap spectrum was measured in the two cell types. Several new hole traps were detected, and significant differences between the homo- and hetero-epitaxial cells were observed. The PV response of both cells types was measured as a function of fluence. The homoepitaxial (InP/InP) data was fit to the standard degradation curve, and the results are used to predict the radiation response of the InP/Si cells. The response of a 16% beginning of life (BOL) InP/Si cell is also predicted and shown to out perform GaAs/Ge cells for fluences above 5×10¹⁴ cm^-2