Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

Suyatin, Dmitry; Jain, Vipul; Небольсин, В. А.; Trägårdh, Johanna; Messing, Maria E.; Wagner, Jakob Birkedal; Persson, Olof; Timm, Rainer; Mikkelsen, Anders; Maximov, Ivan; Samuelson, Lars; Pettersson, Håkan

doi:10.1038/ncomms4221

Cited by 58 publications

(64 citation statements)

References 62 publications

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“…Since these two discussed systems are similar, we conclude that the series of GaPpassivated NWs studied in a recent paper did not have shunts. Similar results for high performance of GaPpassi vated GaAs NWs are reinforced by results from other methods [22,23], including comprehensive theoreti cal interpretation [6]. A reduced Fermilevel pinning was previously suggested as a possible explanation for lowering of Schottky barriers at metalcatalyst/ NW interfaces.…”

Section: Discussionsupporting

confidence: 68%

“…A reduced Fermilevel pinning was previously suggested as a possible explanation for lowering of Schottky barriers at metalcatalyst/ NW interfaces. Authors explained the barrier lower ing by a reduced density of pinning states combined with a formation of an electric dipole layer [6]. For tunately, here this effect has been recorded experi mentally by the contact AFM technique, so that we could generalize the I-V curves to represent them in the logscale and later qualitatively verify the resis tivity of the pGaAs NWs.…”

Section: Discussionmentioning

confidence: 97%

“…Their surfacetovolume ratios are considerably high, while the surface-diameter ratio is also high, which leads to an increase of the influence of surface effects on the NW's electronic properties. The high density of surface states, where electrons and holes can re combine (in GaAs NWs) [6], leads to the near surface depletion and significant decrease in an electrical cur rent through NW, due to immobilization of holes on the surface for ptype GaAs. Moreover, charges can become trapped on surface states, causing local shifts in the electric potential.…”

Section: Introductionmentioning

confidence: 99%

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Influence of surface passivation on electric properties of individual GaAs nanowires studied by current–voltage AFM measurements

Geydt¹,

Alekseev²,

Dunaevskiy³

et al. 2016

Lith. J. Phys.

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Current-voltage (I-V) characteristics of vertical p-GaAs nanowires (NWs) covered by different surface passivation materials were experimentally measured by conductive atomic force microscopy (C-AFM). The obtained I-V curves for individual NWs with a diameter of 100 nm covered with AlGaAs, GaN, GaP or InP shell layers were compared to analyse the influence of surface passivation on the density of surface states and choose the most beneficial passivating material for technological applications. We have found the absence of a Schottky barrier between the golden catalytic cap on the top of a NW and the nanowire situated below and covered with an ultrathin GaP passivating layer. It was suggested that passivating material can arrange the heterostructure configuration with the GaAs NW near the Au cap. The latter mechanism was proposed to explain a strong energy barrier found in nanowires covered with InP passivation. AlGaAs passivation affected the forward threshold voltage of nanowires for NWs, which was measured simultaneously with the resistivity of each individual vertical structure from an array by means of AFM in the regime of measuring the I-V curves and onefold calculations. We made an attempt to develop the methodology of measurement and characterization of electric properties of passivated NWs.

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Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of surface passivation on electric properties of individual GaAs nanowires studied by current–voltage AFM measurements

Geydt¹,

Alekseev²,

Dunaevskiy³

et al. 2016

Lith. J. Phys.

View full text Add to dashboard Cite

show abstract

“…GaAs nanowires are notoriously difficult to form Ohmic electrical contacts with, because the required high temperature annealing steps cause decomposition of the nanowires and because of significant charge carrier depletion due to surface states [16]. This has hampered electrical characterisation of the nanowires and significant effort is currently being invested in improving electrical contacts to GaAs nanowires [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

The influence of surfaces on the transient terahertz conductivity and electron mobility of GaAs nanowires

Joyce

Baig

Parkinson

et al. 2017

J. Phys. D: Appl. Phys.

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“…Unpinning has also been observed for nanocrystalline contacts [42,43] and at metal-semiconductor nanowire interfaces [44]. In the nano-regime, the unpinning was attributed to a reduced density of pinning states [44] and the effect of quantum confinement on band bending [6].…”

Section: Introductionmentioning

confidence: 99%

The role of quantum confinement in the formation of Schottky barriers in Pb–Si interfaces

Chan

Souto-Casares

Chelikowsky

et al. 2015

Solid State Communications

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a b s t r a c tSchottky barriers form when semiconductors are in contact with metal overlayers establishing a common Fermi level. Few theoretical studies of these materials exist as electronic structure calculations are computationally intensive for mismatched interfaces. We explicitly model a Pb(111) film on a Si (111) substrate. For thick Pb overlayers, we find a bulk regime where the Fermi level is pinned. For thin film regimes (less than five overlayers), structural relaxations dominate the interfacial energy as charge transfer is suppressed by quantum confinement. In this case, the Schottky barrier height follows the trend of the metal work function.One of the first models to predict the formation of a Schottky barrier is from Schottky [1,2] and Mott [3] some 70 years ago. The Schottky-Mott theory assumes that the metal and the semiconductor are not strongly interacting at the interface. Under such an assumption the vacuum levels are aligned, and the size of an ntype Schottky barrier Φ B;n ¼ ϕ M Àχ, which is the difference between the work function of the metal, ϕ M , and the electron affinity of the semiconductor, χ. If the Schottky-Mott picture was to be correct, then one might consider altering the barrier by changing the work function of the metal, e.g., by using different metals or by physically changing the thickness of the metal to alter the work function by quantum confinement. For some semiconductors, such as those with a wide band gap, Φ B;n exhibits an increasing trend with larger ϕ M ; however, the Fermi level E Fermi is often pinned within a small range for a given semiconductor regardless of the work function of the metal, especially for small gap semiconductors or elemental semiconductors like Si or Ge [4][5][6]. The Schottky-Mott model was rapidly abandoned for some semiconductor systems because of experimental evidence for a pinned Fermi level [7]. E Fermi when pinned is essentially independent of the metal contact. Bardeen [8] considered the role of surface states, whose theory had been previously developed by Matt [9] and Shockley [10], and argued that these states would control the formation of a dipole at the metal-semiconductor interface and pin E Fermi .Later, Heine [11] and Louie et al. [12,13] refined the ideas of Bardeen by noting that intrinsic surface states could not exist in the presence of an intimate contact with metallic states. They argued that the role played by the surface states pinning E Fermi in the Bardeen model could be played by the tails of intrinsic metallic states, which were capable of penetrating several layers into the semiconductor side. These metal induced gap states (MIGS) have been widely studied theoretically since the mid-1970s. For example, Louie and coworkers [12][13][14][15] used a jellium model for the metal films, replacing the nuclear charges by a uniform electronic charge density.The jellium model removes structural details of a metal overlayer and avoids the complexity of any lattice mismatch between the metal and semiconductor crystal structure...

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Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

Cited by 58 publications

References 62 publications

Influence of surface passivation on electric properties of individual GaAs nanowires studied by current–voltage AFM measurements

Influence of surface passivation on electric properties of individual GaAs nanowires studied by current–voltage AFM measurements

The influence of surfaces on the transient terahertz conductivity and electron mobility of GaAs nanowires

The role of quantum confinement in the formation of Schottky barriers in Pb–Si interfaces

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