Scanning Tunneling Microscopy/Scanning Tunneling Spectroscopy Observation of III–V Compound Semiconductor Nanostructures

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Abstract
InAs submonolayer samples grown on the vicinal (100) GaAs substrates and the self-organized quantum wire structures formed in the (GaP)2(InP)2 short-period superlattices (SLs) on the nominally (100) GaAs substrates by gas-source molecular beam epitaxy (GS-MBE) are studied by scanning tunneling microscopy (STM) and spectroscopy (STS). In the former nanostructures, the STM images show alternating bright stripes (InAs area) and dark stripes (GaAs area), and the bright stripe width increases with the amount of In supplied during growth. A difference is also observed in the I–V curve; the slope dI/ dV is different between the bright and dark areas and shows the same value in each area, although the onset voltage for the current rise is the same in all areas independent of InAs and GaAs areas. In the latter nanostructures, the STM images show alternating bright and dark stripes corresponding to the self-organized wire structures. In this case the onset voltage for the current rise as well as the slope dI/ dV varies depending on the lateral alloy composition modulation in the wire structures.