Temperature-dependent Al/GaAs(110) interface formation and adatom energy references

Anderson, Susan; Aldao, C. M.; Waddill, G. D.; Severtson, Steve J; Weaver, J. H.

doi:10.1103/physrevb.40.8305

Cited by 22 publications

(4 citation statements)

References 35 publications

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“…A key to understanding the electronic properties of the interface is the determination of the atomic structures at the various stages of growth. Although cluster formation and exchange reactions at metal-semiconductor interfaces have been confirmed [1][2][3][4][5][6], such determination has not yet been carried out for any interface. GaAsO 10) is one of most widely studied semiconductor surfaces.…”

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confidence: 99%

Atomic structure of Al-GaAs(110) interfaces

Bernholc

1992

Phys. Rev. Lett.

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Atomic structures of Al on GaAsO 10) are studied by ab initio molecular dynamics for coverages of j to 1 monolayer (ML). A single chemisorbed Al atom resides at the center of a triangle of one Ga and two As atoms. Al dimers have very long bond lengths and bind due to substrate-mediated interactions. Epitaxial growth of 1 ML of Al is less stable than the formation of islands. Preformed clusters bond strongly to the substrate, which shows that the absence of Fermi-level pinning in samples grown by cluster deposition is due to suppression of reactivity rather than lack of interactions.

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confidence: 99%

Atomic structure of Al-GaAs(110) interfaces

Bernholc

1992

Phys. Rev. Lett.

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“…Metals deposited directly on similarly doped substrates showed clear evidence of SPV effects in the temperature dependence of the barrier and shunting of the SPV at a metal coverage 10 Å. 77,78 In the case of cluster deposited metals, the PES barrier height was found to be independent of temperature and showed no shunt effect step in the PES barrier height up to the maximum ͑effective͒ metal coverage of 34 Å, three times that required for the case of directly deposited metals. 73,79 Although the lack of a temperature-dependent barrier contradicts the assumption of an SPV effect the unusual pinning point at E c Ϫ0.3 eV still raises the question as to whether an, as yet, unidentified mechanism may be affecting the data.…”

Section: Namementioning

confidence: 96%

Schottky barriers on GaAs: Screened pinning at defect levels

Drummond

1999

Phys. Rev. B

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Schottky barrier heights on n-type GaAs can be made to vary from 0.30 to 1.20 eV by adjusting the conditions under which the Schottky contact is fabricated. To explain the observed trends it is asserted ͑a͒ that there are several defect pinning points associated with GaAs surfaces, ͑b͒ that an appropriate interfacial permittivity may be defined to predict the barrier height from the metal work function and the position of the appropriate pinning point, and ͑c͒ the pinning point is sensitive to the metal-GaAs reaction chemistry. In a thermodynamic context the present analysis is an electronegativity model. The work function of a polycrystalline metal and the charge neutrality level of the semiconductor are interpreted as the bulk chemical potentials of the two materials. When the two materials are brought into contact electronegativity equalization takes place as charge is transferred across the interface in the formation of metal-semiconductor bonds. Proper derivation of the equilibrium bond charge dipole requires a knowledge of the chemical ''softness'' of the two surfaces being brought into contact as well as the electronegativity difference of the two materials. The equilibrium dipole determines the barrier height of an ''ideal interface Schottky contact.'' A description is given of how the softness of metal and semiconductor surfaces may be defined and how near surface defects in the semiconductor modify the interfacial dipole. The strength of the model is in its descriptive power as it can identify the specific native defects at which pinning is observed in GaAs Schottky diodes. It provides a framework for the development of a predictive model based on identifying the particular native defects produced by the reaction of specific metals with a semiconductor as a function of the process history. ͓S0163-1829͑99͒09507-7͔The original Schottky-Mott description of Schottky barriers on n-type semiconductors predicts the barrier height to be the difference between the semiconductor electron affinity and the metal work function. In practice, Schottky barrier heights on semiconductors are only weakly dependent on the metal work function. Bardeen attributed this to the presence of semiconductor surface states. 1 Models have been proposed in which the surface states are primarily intrinsic or extrinsic in origin. Intrinsic surface states are commonly referred to as virtual gap states ͑ViGS͒ or metal induced gap states ͑MIGS͒. 2-7 It has been asserted that there is a ''charge neutrality level'' ͑CNL͒ in the semiconductor defined by the character of the ViGS when averaged over the entire Brillouin zone. At some energy the average character of the gap states changes from predominantly valence-band-like to conduction-band-like. The crossover point defines the CNL. The ViGS model asserts that when the CNL ͑relative to vacuum͒ aligns exactly with a metal Fermi level E Fm ͑rela-tive to vacuum͒ there will be a zero net charge dipole at the metal-semiconductor ͑MS͒ interface. This immediately defines the CNL as the location of t...

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“…Metal-GaAs(110) has been considered as a prototype interface and a sizeable amount of experimental data, e.g., obtained by core-level photoelectron spectroscopy, scanning tunnelling microscopy and electron energy loss spectroscopy, on these systems has recently been acquired, which highlight the effects of band bending and the shift of the Fermi level E F [3][4][5][6][7][8][9][10][11][12][13][14][15]. Theoreticians have split the analysis of band bending and shift of the Fermi level into two groups, one for small metal coverage (θ 1 monolayer (ML)) for which the Fermi level movement exhibits a logarithmic dependence on θ, independent of the metal, and one for large metal coverages for which θ > 1, and the final pinning position depends explicitly on the specific interactions at the metal-GaAs interface.…”

Section: Introductionmentioning

confidence: 99%

Observation of Pumping Reaction in an Amine-Based All Gas-Phase Iodine Laser Medium

Masuda¹,

Nakamura

Endo

et al. 2009

jjap

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Different possible adsorption sites of rubidium atoms on a GaAs(110) surface have been investigated using ab-initio self-consistent Hartree-Fock energy cluster calculations followed by detailed correlation investigations at the level of fourth-order many-body perturbation theory. The Hay-Wadt effective core potentials have been used to represent the cores of the rubidium, gallium and arsenic atoms. We find that the Rb atom adsorption at a site modelled with a RbGa 5 As 4 H 12 cluster is most favoured energetically followed by Rb adsorption at a site modelled with a RbGa 4 As 5 H 12 cluster. Significant charge transfer from the Rb atom to the GaAs surface is also found to occur, with Ga atoms losing charge and As atoms gaining charge. Finally, comparisons are made among different alkali atom adsorptions on the GaAs(110) surface.

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Temperature-dependent Al/GaAs(110) interface formation and adatom energy references

Cited by 22 publications

References 35 publications

Atomic structure of Al-GaAs(110) interfaces

Atomic structure of Al-GaAs(110) interfaces

Schottky barriers on GaAs: Screened pinning at defect levels

Observation of Pumping Reaction in an Amine-Based All Gas-Phase Iodine Laser Medium

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