It is demonstrated that the energy band gap in epitaxial layers is changed by biaxial elastic strains which are produced by lattice mismatches in heterostructures. The epitaxial layers used in this work were Gax In1−xP layers grown on (001) GaAs substrates by liquid phase epitaxy. The energy band-gap shifts were determined by comparing the photoluminescence peak energies of the as-grown GaxIn1−xP layers with those from free-standing layers removed from the GaAs substrates. It was experimentally found that the energy band gap shifts linearly with the elastic strain in the layer. Assuming that the lattice mismatch was accommodated only by the elastic distortion, the energy band-gap shifts in Ga0.5In0.5P alloys were also calculated. The calculated results are 6.0 eV or 4.9×10−12 eV/dyn cm−2 per unit strain or stress, respectively, for the [100] and [010] biaxial elastic stress. These values are in quite good agreement with the experimental results.

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Lateral epitaxial growth of GaAs over tungsten gratings of 5-μm wide lines and spaces on (001) GaAs substrates has been performed using metalorganic chemical vapor deposition (MOCVD). The lateral overgrowth is strongly dependent on the grating direction on the (001) plane, as well as on the growth temperature. A vertical field effect transistor with a grating gate of 1.25-μm wide lines and spaces is demonstrated as one application of this MOCVD overgrowth technique. The drain I-V characteristics of the device are similar to those for a triode tube.