Electron transport measurements of Schottky barrier inhomogeneities

Calvet, Laurie E.; Wheeler, R. G.; Reed, Mark A.

doi:10.1063/1.1456257

Cited by 59 publications

(42 citation statements)

References 20 publications

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“…This may be due to the sensitivity of the Schottky interfaces to preparation procedures and to different techniques of measuring the BH [17]. In recent years, studies of SBH inhomogeneities have been carried out [16,19,[23][24][25][26][27][28][29][30]. Freeouf et al [23] reported on the influence of a small patch with a low BH within the contact area on the ideality factor and the essence of the contact area size in this effect.…”

Section: Introductionmentioning

confidence: 99%

Correlation Between Barrier Heights and Ideality Factors of Ni/n-Ge (100) Schottky Barrier Diodes

Chawanda

Nel²,

Auret³

et al. 2010

J. Korean Phy. Soc.

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We computed the homogeneous Schottky barrier height (SBH) at ideality factor (n) = 1.0 of Ni/nGe (100) Schottky diodes (SDs). The SDs were identically prepared by using resistive evaporation of Ni on n-Ge (100). The SBHs and n of these diodes (24 dots) were calculated from their experimental forward bias current-voltage (I-V ) and reverse bias capacitance-voltage (C-V ) measurements at room temperature. Even though the Schottky diodes were identically prepared, the values of the SBH from the I-V characteristics varied from 0.487 to 0.508 eV, the ideality factor varied from 1.34 to 1.53, and the SBH from the C −2 -V characteristics varied from 0.358 to 0.418 eV. The Gaussian fits of the experimental SBH distributions obtained from the C −2 -V and the I-V characteristics yielded mean SBH values of 0.401 ± 0.015 and 0.503 ± 0.006 eV, respectively. Furthermore, a homogeneous SBH value of approximately 0.535 eV was also computed from an extrapolation of a linear plot of the experimental SBHs versus the ideality factors. The homogeneous SBHs, rather than the effective SBHs, of individual contacts or mean values should be used to discuss the theories and the physical mechanisms that determine the SBHs of SDs.

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Section: Introductionmentioning

confidence: 99%

Correlation Between Barrier Heights and Ideality Factors of Ni/n-Ge (100) Schottky Barrier Diodes

Chawanda

Nel²,

Auret³

et al. 2010

J. Korean Phy. Soc.

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“…In this regime, single dopant atoms have been demonstrated to dominate the behavior of downscaled versions of conventional devices. 1 On the other hand, the promising opportunity is offered to study the physics of semiconductors on their ultimate length scale by addressing separate dopants. Putting a small gate close to a single impurity would, for example, allow for the manipulation of individual hydrogenlike wave functions.…”

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confidence: 99%

Gate-induced ionization of single dopant atoms

et al. 2003

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Gate-induced wave function manipulation of a single dopant atom is a possible basis of atomic scale electronics. From this perspective, we analyzed the effect of a small nearby gate on a single dopant atom in a semiconductor up to field ionization. The dopant is modeled as a hydrogenlike impurity and the Schrödinger equation is solved by a variational method. We find that-depending on the separation of the dopant and the gate-the electron transfer is either gradual or abrupt, defining two distinctive regimes for the gate-induced ionization process. DOI: 10.1103/PhysRevB.68.193302 PACS number͑s͒: 03.67.Lx, 85.30.De, 73.21.Ϫb, 71.55.Ϫi The size regime where the discreteness of doping must be taken into account is brought within experimental reach by today's semiconductor lithography techniques. In this regime, single dopant atoms have been demonstrated to dominate the behavior of downscaled versions of conventional devices. 1 On the other hand, the promising opportunity is offered to study the physics of semiconductors on their ultimate length scale by addressing separate dopants. Putting a small gate close to a single impurity would, for example, allow for the manipulation of individual hydrogenlike wave functions. Furthermore, large electric fields ͑otherwise only achievable in astronomy͒ can be experimentally obtained in semiconductors due to the occurrence of large dielectric constants and small effective masses. Apart from the fundamental importance, an ultimate application is found in a Si-based solid state quantum computer, 2,3 in which the nuclear spins of single 31 P dopants are envisioned as qubits. In this proposal, addressing a single qubit by nuclear magnetic resonance is achieved via the hyperfine interaction of the nuclear spin and its valence electron, which can be tuned by modifying the electron wave function with a nearby gate. In a recent variation of this design, 4 the ionization of single dopants by this gate is an essential ingredient.Our aim is to quantitatively investigate the effect of the electric field generated by a local gate on a single neutral dopant atom in a semiconductor, ultimately leading to ionization. The response to small fields has been addressed before in the context of quantum computing. 5,6 In this paper, the complete ionization process is discussed. Our approach incorporates the computation of time independent ground state wave functions of the system and, subsequently, the estimation of transition probabilities. We conclude that the separation of the dopant and the gate determines the nature of the ionization process. When the dopant resides close to the gate, the electron is gradually pulled away from the dopant when the gate voltage is increased, while for a larger separation the dopant ionizes abruptly at a well-defined gate voltage.Addressing a single dopant requires a small local gate. When a dopant would be ionized by a large gate ͑e.g., an infinite strip 6 ͒, the electron would be delocalized along the gate. This would be undesirable in applications where ͑sp...

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“…However, tunneling spectroscopy of impurity states can also be done with microfabricated devices, such as nano-sized Schottky diodes [40], nanosized field effect transistors [41][42][43][44] or nanosized memristors [45]. In this work, we present an observation of Shiba bound states forming in a dopantinduced impurity band.…”

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confidence: 82%

Shiba Bound States across the Mobility Edge in Doped InAs Nanowires

et al. 2017

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We present a study of Andreev Quantum Dots (QDots) fabricated with small-diameter (30 nm) Si-doped InAs nanowires where the Fermi level can be tuned across a mobility edge separating localized states from delocalized states. The transition to the insulating phase is identified by a drop in the amplitude and width of the excited levels and is found to have remarkable consequences on the spectrum of superconducting SubGap Resonances (SGRs). While at deeply localized levels, only quasiparticles co-tunneling is observed, for slightly delocalized levels, Shiba bound states form and a parity changing quantum phase transition is identified by a crossing of the bound states at zero energy. Finally, in the metallic regime, single Andreev resonances are observed.In superconductor-QDot-superconductor structures or at impurities in bulk superconductors, Bogoliubov type bound states can form at energy smaller than the superconducting gap energy ∆, leading to SGRs.The SGR formation depends on the different energy scales: ∆, the coupling Γ S of the QDot with the superconducting electrodes, the charging energy, U, and the energy, ε 0 , of the QDot level relative to the Fermi energy of the superconducting electrodes. Its phase diagram has been extensively studied theoretically [1,2]. For large coupling Γ S , the SGRs result from the coherent superposition of multiple Andreev reflections [3,4] and conductance peaks are expected at voltage values ∆/ne [5] where n is the number of Andreev reflections. For weak coupling Γ S , where the system is in the regime of Coulomb blockade, the ground state, singlet |S or doublet |D , results from the competition between the Kondo screening and the superconducting pairing interaction. These two ground states are separated by a parity changing quantum phase transition, which can be identified by the crossing of the SGRs at zero-energy. Previous works have addressed this transition through measurements of Josephson supercurrents [6][7][8][9][10] and studies of the SGRs in S-QDot-S [11][12][13][14][15][16][17] or N-QDot-S geometries [18][19][20][21]. Recently, similar devices attracted intense interest with the observation of the zero-energy Majorana end states in proximitized nanowires [22][23][24].The physics of odd parity QDot is related to the physics of Shiba states [25][26][27][28][29] forming at magnetic impurities in bulk superconductors, where tuning the magnetic exchange also leads to a parity changing quantum phase transition [30][31][32][33][34][35][36] [45]. In this work, we present an observation of Shiba bound states forming in a dopantinduced impurity band. In this diffusive regime, it is expected that an Anderson-like Metal-Insulator Transition (MIT) [46] separates the metallic regime at high carrier concentration from an insulating regime at low carrier concentration, where the localized and delocalized states in the band structure are separated in energy by a mobility edge. We identified this mobility edge in the conductance spectrum measured as function of gate voltage and sho...

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Electron transport measurements of Schottky barrier inhomogeneities

Cited by 59 publications

References 20 publications

Correlation Between Barrier Heights and Ideality Factors of Ni/n-Ge (100) Schottky Barrier Diodes

Correlation Between Barrier Heights and Ideality Factors of Ni/n-Ge (100) Schottky Barrier Diodes

Gate-induced ionization of single dopant atoms

Shiba Bound States across the Mobility Edge in Doped InAs Nanowires

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