Atomic diffusion and interface electronic structure at In0.49Ga0.51P/GaAs heterojunctions

We have performed cross-sectional cathodoluminescence spectroscopy and secondary ion mass spectrometry measurements of lattice-matched, SiOx-capped In0.49Ga0.51P/GaAs double heterostructures (DHs) in order to investigate the relation between chemical interactions and localized electronic states at the epitaxial heterojunction. We measure atomic diffusion of over 100 nm resulting from anneals ranging from 650 to 850 degrees C. A 20 meV increase in the near-band-edge (NBE) emission energy of InGaP is observed after the highest temperature anneals. This increase is consistent with an increase in the Ga concentration of the ternary layer as a result of diffusion from neighboring GaAs layers. Additionally, we observe InGaP/GaAs interface-localized features at similar to 1.49 and similar to 1.37 eV. The intensity of these emissions relative to the band-edge emission of the underlying layer depends sensitively on the anneal temperature and corresponding diffusion. These results reveal a correlation between cross diffusion and defect emission at InGaP/GaAs interfaces. They clarify the nature of the cross diffusion and reactions that occur at these interfaces in SiOx-capped structures, and those may be expected to occur during interface growth or processing at elevated temperatures. It is demonstrated that these chemical effects can have a significant impact on the electronic structure of lattice-matched III-V heterostructures. (C) 2008 American Vacuum Society.