Minority carrier lifetime of GaAs on silicon

AlGaAs/GaAs double heterostructures for solar cells were grown on heteroepitaxial GaAs/Si layers by metal-organic chemical vapor deposition. These test devices were subsequently characterized by photoluminescence and transmission electron microscopy. The minority carrier lifetimes were found to be limited by recombination at mismatch dislocations. An inverse correlation between dislocation density and minority carrier lifetime was observed. The use of thick (8 mu m) GaAs buffer layers in conjunction with thermal annealing of these structures reduced the dislocation density by about an order of magnitude. The minority carrier lifetime in these buffered heterostructures increased from 0.1 to 2 ns.