Compositional modulation in AlxGa1−xAs epilayers grown by molecular beam epitaxy on the (111) facets of grooves in a nonplanar substrate
We report the first observation of a lateral junction formed in an alloy due to an abrupt transition from segregated to random AlGaAs alloy compositions. Al0.25Ga0.75As epilayers were grown by molecular beam epitaxy on [011-bar] oriented grooves in a nonplanar (100) GaAs substrate. A quasi-periodic modulation of the aluminum concentration occurs spontaneously in material grown on the (111) facets of the groove, with a period of 50–70 Å along the  direction. The compositional modulation is associated with a reduction of the band gap by 130 meV, with respect to the random alloy. While segregation of the AlGaAs alloy has been seen previously, this is the first observation of segregation of AlGaAs grown on a (111) surface. The compositional modulation terminates abruptly at the boundaries of the (111) facet, forming abrupt lateral junctions in the AlGaAs layers grown on a groove.
Additional InformationCopyright © 1989 American Institute of Physics. Received 20 March 1989; accepted 18 April 1989. This work was supported by the Office of Naval Research. The transmission electron microscopy was supported by the National Science Foundation-Materials Research Group grant number DMR 8811795. The authors would like to thank Professor Amnon Yariv for supplying the molecular beam epitaxy growths used in these experiments.
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