Structural and chemical studies of novel 1-eV band gap solar cell materials lattice-matched to GaAs

Novel 1-eV band gap materials, of interest for high-efficiency, multijunction solar cells, grown by metal-organic vapour-phase epitaxy on GaAs substrates, have been studied. Ga_1-xIn_xN_yAs_1-y layers grown at 650°C, using dimethylhydrazine as a nitrogen source, contained a high density of ‘comet’-like defects that generated threading dislocations. GaN_yAs_1-y layers grown at 550°C using hydrazine were found to become nanocrystalline or amorphous at high hydrazine/III flow ratios. Epitaxial growth of zinc-blende B_xGa_1-x-yIn_yAs with up to 3%-5% boron has been achieved. For higher boron concentrations, the layers became polycrystalline or amorphous.