TRANSMISSION ELECTRON-MICROSCOPY STUDIES OF GAAS ALGAAS HETEROSTRUCTURES REGROWN ON PATTERNED SUBSTRATES/

The structure of GaAs quantum wires embedded in Al0.33Ga0.67As and the interfaces between the wires and the matrix were investigated by tran smission electron microscopy (TEM) in diffraction-contrast and high-re solution (HREM) modes. The quantum wires were regrown by molecular bea m epitaxy (MBE) On patterned Al0.33Ga0.67As buffer layers on GaAs subs trates. Depending on the orientation of the quantum wires within the ( 100) surface of the substrate, different characteristic facets develop during MBE regrowth of the mesa-etched samples. The surface structure for [011]- and [0 (1) over bar 1]-oriented wires is dominated by (111 ) and (311) facets. The (111) planar defects like stacking faults and twins are frequently observed in the case of (111) facet growth. Mainl y (110) facet formation is found for [001]- and [010]-oriented wires; planar defects are not detected in this case.