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ABSTRACT: The local density of states (LDOS) of InAs/GaSb long period superlattices was investigated on the cleaved (110) surface at atomic resolution by low-temperature scanning tunneling microscopy and low-temperature scanning tunneling spectroscopy (LT-STS). We present definitive features showing the broken-gap energy band profiles (the overlap of the conduction band of the InAs and the valence band of the GaSb in energy) in the LT-STS spectra complemented by distinct, atomically resolved topographic images. Furthermore, vivid standing waves in LDOS corresponding to the single quantum well-like subband confined in the InAs layer were observed.
Journal of Applied Physics 04/2007; 101(8):081705-081705-4. · 2.17 Impact Factor
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ABSTRACT: Low-temperature scanning tunneling spectroscopy under ultra-high vacuum was employed to investigate the two-dimensional electron system at the epitaxial surface of Sidoped In0.53Ga0.47As/In0.52Al0.48As(111)A quantum-well structures. The electron density in the near-surface region of the quantum well could be controlled through modulation doping. Spectra of the electronic local density of states in the conduction band showed a clear step-like energy dependence that reveals the subband states. In spectra acquired at some areas of nanometer size, peaks were observed near subband minima, indicating the existence of bound states.
Journal of Physics Conference Series 04/2007; 61(1):926.
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ABSTRACT: We measure the spatial distribution of the local density of states (LDOS) at cleaved surfaces of InAs/GaSb isolated quantum wells and double quantum wells (DQWs) by low-temperature scanning tunneling spectroscopy. Distinct standing wave patterns of LDOS corresponding to subbands are observed. These LDOS patterns and subband energies agree remarkably well with simple calculations with tip-induced band bending. Furthermore, for the DQWs, coupling of electronic states between the quantum wells is also clearly observed.
Physical Review Letters 04/2007; 98(13):136802. · 7.37 Impact Factor
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ABSTRACT: The local density of states at cleaved cross-sectional surfaces of InAs/GaSb superlattices were investigated by low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) with atomic resolution. Broken-gap energy band profiles (the overlap of the conduction band of InAs and the valence band of GaSb) were clearly seen in the LT-STS spectra as a function of growth direction. Clear images of electron standing waves confined in the superlattice were also obtained. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (c) 02/2006; 3(3):643 - 646.
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ABSTRACT: The local density of states (LDOS) within tetrahedral InAs structures, formed at the surface of InAs/GaAs(111)A, has been characterized using low-temperature scanning tunneling microscopy. The LDOS of the lowest four zero-dimensional (0D) discrete levels have been imaged in structures with a comparable size to the electron wavelength. The LDOS inside the structures is observed to be higher than that of the surrounding area at intervals of the level separation. This feature indicates the singularity of the LDOS close to the 0D resonant levels.
Physical Review Letters 12/2001; 87(19):196804. · 7.37 Impact Factor
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ABSTRACT: The local density of states (LDOS) at the epitaxially grown InAs surface on a GaAs(111) A substrate were characterized using low-temperature scanning tunneling microscopy. Using dI/dV signal mapping, LDOS standing waves were clearly imaged at point defects and within nanostructures. Measurement of the wavelength as a function of bias voltage showed a nonparabolic dispersion relation for the conduction band. The observed wave features originate from the Friedel oscillations of the two-dimensional electron gas in the semiconductor surface accumulation layer.
Physical Review Letters 05/2001; 86(15):3384-7. · 7.37 Impact Factor
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ABSTRACT: Heteroepitaxy of high-quality InSb films was performed directly on GaAs surfaces by using molecular beam epitaxy. Despite the 14.6% lattice mismatch, two-dimensionally grown InSb on GaAs(111)A substrates were obtained from the initial stage, but not on (001) substrates. A conductive layer was formed from the early stage of the growth on the (111)A surface, and the mobilities and carrier concentrations of InSb on (111)A substrates suggested a low defect density due to confinement of the dislocations to the interface. © 2000 American Institute of Physics.
Applied Physics Letters 01/2000; 76(5):589-591. · 3.84 Impact Factor
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ABSTRACT: We successfully grew an atomically smooth 14.6% lattice-mismatched InSb layer on GaAs substrates under the Frank-van der Merwe (F-vdM) mode from the beginning of molecular beam epitaxy (MBE) by eliminating excess Sb adsorption. It is confirmed that the use of a (111)A substrate and an In template layer has an advantage in the enhancement of layer-by-layer InSb growth on a GaAs substrate. Characterization with scanning tunneling microscopy (STM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) clarified that we achieved a 1 nm height difference per 1 μm<sup>2</sup> area, which is comparable to that of a homoepitaxially grown GaAs surface
Indium Phosphide and Related Materials, 1998 International Conference on; 06/1998
