Defects in GaAs solar cells with InAs quantum dots created by proton irradiation

GaAs pn-junction diodes with embedded InAs quantum dots (QDs) are irradiated with protons and the generated deep level traps are investigated using Deep Level Transient Spectroscopy (DLTS). The results are compared to GaAs pn-junction diodes without QDs in order to identify the origin of the deep level traps. The fluence dependence of trap density is investigated, and it is shown that majority carrier (electron) traps induced by irradiation increase in proportion to the fluence whereas the EL2 trap, which appears before irradiation, is not affected by irradiation. In addition, 0.14 eV minority carrier (hole) traps in the QD layer are found by using forward biased injection technique and it is shown that this unique trap is unaffected by irradiation. Electron and hole emission from QD levels are also discussed.