Suppression of low-frequency noise in two-dimensional electron gas at degenerately doped Si:P<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>δ</mml:mi></mml:mrow></mml:math>layers

Shamim, Saquib; Mahapatra, S.; Polley, Craig; Simmons, M. Y.; Ghosh, Arindam

doi:10.1103/physrevb.83.233304

Cited by 18 publications

(20 citation statements)

References 30 publications

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“…As shown in the inset of Fig. 1f, A×S I I 2 sd from the devices collapse at all V g , implying S I I 2 sd ∝ 1 A, which is expected when noise originates from the channel region [56]. (The 1 A dependence was not observed in the pre-annealed noise.)…”

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confidence: 90%

Percolative switching in transition metal dichalcogenide field-effect transistors at room temperature

2016

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We have addressed the microscopic transport mechanism at the switching or "on-off" transition in transition metal dichalcogenide (TMDC) field-effect transistors (FET), which has been a controversial topic in TMDC electronics, especially at room temperature. With simultaneous measurement of channel conductivity and its slow time-dependent fluctuation (or noise) in ultra-thin WSe2 and MoS2 FETs on insulating SiO2 substrates, where noise arises from McWhorter-type carrier number fluctuations, we establish that the switching in conventional backgated TMDC FETs is a classical percolation transition in a medium of inhomogeneous carrier density distribution. From the experimentally observed exponents in the scaling of noise magnitude with conductivity, we observe unambiguous signatures of percolation in random resistor network, particularly in WSe2 FETs close to switching, which crosses over to continuum percolation at a higher doping level. We demonstrate a powerful experimental probe to the microscopic nature of near-threshold electrical transport in TMDC FETs, irrespective of the material detail, device geometry or carrier mobility, which can be extended to other classes of 2D material-based devices as well.The expanding family of atomically thin layers of semiconducting TMDC materials for electronic [1][2][3][4][5][6][7], optoelectronic [8][9][10][11][12][13][14], valleytronic [15][16][17][18][19] and even piezoelectronic [20] applications, has defied a generic framework of electron transport because of diverse material quality, channel thickness dependent band structure, dielectric environment, and nature of substrates. A wide variety of physical phenomena ranging from variable range hopping [5], metal-insulator transition [7] to classical percolative charge flow through inhomogeneous medium [21,22] were reported for MoS 2 , the implications of which often lead to a conflicting microscopic scenario. At low carrier density, for example, hopping via single particle states trapped at short-range background potential fluctuations (∼few lattice constants [23]) is incompatible to the observation of classical percolative conduction that requires long-range inhomogeneity in charge distribution, created when linear screening of the underlying charge disorder breaks down [24][25][26][27]. Observations of metal-insulator transition [7,22] [21,24,25,[40][41][42][43][44], but the experimental difficulty lies in accurately determining the fraction p of the conducting region, or "puddles", embedded inside the insulating matrix. Hence despite compelling evidence of long range inhomogeneity in the charge distribution in MoS 2 FETs [21,22], its manifestation in transport remains indirect and confined only to low temperatures. A way to circumvent this difficulty involves measuring the lowfrequency noise, or 1 f -noise, in the channel conductivity σ, which also scales with p with independent characteristic scaling exponents [40,42], and diverges at the percolation threshold (p c ) [41]. A direct relation between the normalized noise...

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confidence: 90%

Percolative switching in transition metal dichalcogenide field-effect transistors at room temperature

2016

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“…2a) are analyzed to obtain the power spectral density, S G , which on integration over the experimental bandwidth gives the normalized variance, Fig. 2a (see Ref [30] and SI, section S3 for details). Fig.…”

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Spontaneous Breaking of Time-Reversal Symmetry in Strongly Interacting Two-Dimensional Electron Layers in Silicon and Germanium

et al. 2014

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We report experimental evidence of a remarkable spontaneous time reversal symmetry breaking in two dimensional electron systems formed by atomically confined doping of phosphorus (P) atoms inside bulk crystalline silicon (Si) and germanium (Ge). Weak localization corrections to the conductivity and the universal conductance fluctuations were both found to decrease rapidly with decreasing doping in the Si:P and Ge:P δ−layers, suggesting an effect driven by Coulomb interactions. In-plane magnetotransport measurements indicate the presence of intrinsic local spin fluctuations at low doping, providing a microscopic mechanism for spontaneous lifting of the time reversal symmetry. Our experiments suggest the emergence of a new many-body quantum state when two dimensional electrons are confined to narrow half-filled impurity bands.Invariance to time reversal is among the most fundamental and robust symmetries of nonmagnetic quantum systems. Its violation often leads to new and exotic phenomena, particularly in two dimensions (2D), such as the quantized Hall conductance in semiconductor heterostructures [1], the quantum anomalous Hall effect in topological insulators [2] or the predicted chiral superconductivity in graphene [3]. The breaking of time reversal invariance is experimentally achieved either by an external magnetic field or intentional magnetic doping. Here we show that strong Coulomb interactions can also lift the time reversal symmetry in nonmagnetic 2D systems at zero magnetic field.While bulk P-doped Si and Ge have been extensively studied in the context of electron localization in three dimensions [4][5][6][7][8][9], confining the dopants to one or few atomic planes (δ−layers) of the host semiconductor has recently led to a new class of 2D electron system [10][11][12][13]. Electron transport in these atomically confined 2D layers occurs within a 2D impurity band where the effective Coulomb interaction is parameterized in terms of U/γ, with U being the Coulomb energy required to add an additional electron to a dopant site, and γ, the hopping integral between adjacent dopants. Since each dopant P atom contributes one valence electron, the impurity band is intrinsically 'half filled' (schematic in Fig. 1a), which reinforces the interaction effects due to the inbuilt electron-hole symmetry, and forms an ideal platform to explore the rich phenomenology of the 2D MottHubbard model, ranging from Mott metal-insulator transition (MIT) to novel spin excitations and magnetic ordering [14][15][16][17].In this Letter we show evidence of spontaneously broken time reversal symmetry in 2D Si:P and Ge:P δ-layers as the on-site effective Coulomb interaction is increased by decreasing the doping density of P atoms. Quantum transport and noise experiments indicate a strong suppression of quantum interference effects at low doping densities. We could attribute this to a spontaneous breaking of time reversal symmetry which manifest in an unambiguous suppression of universal conductance fluctuations (UCF) at zero magnetic fiel...

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“…[35][36][37] This work shows that with precision single atom fabrication technologies with epitaxial monolayer doped gates we can apply voltages up to GHz frequencies to control the spin states of the qubits. With the recent demonstration of the suppression of charge noise in these systems [12][13][14] this bodes well for precision donor based qubits in silicon. Furthermore, a correction factor ∼ = 0.75 estimated via the ∆V pulsed ∆V Gs ≈ 150 200 of the V-shape in Fig.…”

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Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies

et al. 2016

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The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

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Suppression of low-frequency noise in two-dimensional electron gas at degenerately doped Si:Pδlayers

Cited by 18 publications

References 30 publications

Percolative switching in transition metal dichalcogenide field-effect transistors at room temperature

Percolative switching in transition metal dichalcogenide field-effect transistors at room temperature

Spontaneous Breaking of Time-Reversal Symmetry in Strongly Interacting Two-Dimensional Electron Layers in Silicon and Germanium

Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies

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