GROWTH AND CHARACTERIZATION OF GAAS/AL/GAAS HETEROSTRUCTURES

Theoretical and experimental aspects of the growth of GaAs/Al/GaAs heterostructures have been investigated. In these heterostructures the GaAs on top of the buried metal layer is grown by migration-enhanced epitaxy (MEE) at low temperatures (200 and 400 °C) to provide a kinetic barrier to the outdiffusion of Al during superlayer growth. The crystallinity and orientation of the Al film itself deposited on (100) GaAs at ∼0 °C was studied by transmission electron diffraction, dark-field imaging, and x-ray diffraction measurements. It is found that the Al growth is polycrystalline with a grain size ∼60 Å and the preferred growth orientation is (111), which may be textured in plane but oriented out of plane. The quality of the GaAs superlayer grown on top of Al by MEE is very sensitive to the growth temperature. The layer grown at 400 °C has good structural and optical quality, but is accompanied by considerable outdiffusion of Al at the Al-GaAs heterointerface. At 200 °C, where the interface has good structural integrity, the superlayer exhibits twinning and no luminescence is observed.