Influence of doping density on electronic transport in degenerate Si:P<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>δ</mml:mi></mml:math>-doped layers

Goh, Kuan Eng Johnson; Oberbeck, L.; Simmons, M. Y.; Hamilton, A. R.; Butcher, M. J.

doi:10.1103/physrevb.73.035401

Cited by 67 publications

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References 26 publications

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“…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.…”

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confidence: 99%

“…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 field.The preparation of the P δ-layers in Si and Ge have been detailed in earlier publications [10,11,18], and parameters relevant to the present work is supplied in the Supplementary Information (SI). The Drude conductivity (σ D ) of the δ-layers decreases with decreasing doping as σ D ∝ n 3/2 (Fig.…”

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confidence: 99%

“…The preparation of the P δ-layers in Si and Ge have been detailed in earlier publications [10,11,18], and parameters relevant to the present work is supplied in the Supplementary Information (SI). The Drude conductivity (σ D ) of the δ-layers decreases with decreasing doping as σ D ∝ n 3/2 ( 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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Spontaneous Breaking of Time-Reversal Symmetry in Strongly Interacting Two-Dimensional Electron Layers in Silicon and Germanium

et al. 2014

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“…Delta-doped quantum wells in Si are ideal structures to study the transport properties of ultra dense two dimensional electron gases (2DEG) [9,10] Important parameters are the mobility, mean free path and phase coherent length due to their implications in ballistic and coherent nanodevices. Meanwhile the carrier concentration in this kind of systems is ultra high, the mobility is very low, which is opposite to what happen in GaAs/AlGaAs systems [11].…”

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confidence: 99%

Electron Subband Structure and Mobility Trends in P-N Delta-Doped Quantum Wells in Si

Ariza-Flores

Rodrı́guez-Vargas²

2008

PIER Letters

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Abstract-We present the electronic spectrum of a n-type deltadoped quantum well in Si coupled to a p-type delta-doped barrier within the envelope function effective mass approximation. We applied the Thomas-Fermi approximation to derive an analytical expression for the confining potential, and thus, we obtain the electronic structure in a simple manner. We analyzed the electron subband structure varying the distance between the doping planes (l) as well as the impurity density in them (n 2D , p 2D ). We also study the mobility trends through an empirical formula that is based on the electron levels, the electron wave functions and the Fermi level. We find a monotonic decrease in the mobility as the p-type barrier moves away from the n-type well, and optimum parameters, l = 70Å and n 2D = 5 × 10 12 cm −2 and p 2D = 5 × 10 13 cm −2 , for maximum mobility.

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“…So, the delta-doped quantum wells in Si are ideal structures to study the transport properties of ultradense two dimensional electron gases (2DEG) [2,3] These works make emphasis in parameters such as the mobility, mean free path, and phase coherent length due to their implications in ballistic and coherent nanodevices. Meanwhile the carrier concentration in this kind of systems is ultra high, the mobility is very low, which is opposite to the behavior in GaAs/AlGaAs systems [4].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the Electronic Confinement Improves the Mobility in P-N-P Delta-Doped Quantum Wells in Si

Ariza-Flores¹,

Rodrı́guez-Vargas²

2008

PIER Letters

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Abstract-The electronic structure and mobility trends in a n-type delta-doped quantum well in Si, matched between p-type delta-doped barriers of the same material, is presented. The distance between the n-type well and p-type barriers is varied from 50Å to 500Å; and also the impurity density from 5 × 10 12 cm −2 to 5 × 10 13 cm −2 , for both, donors and acceptors. An increase in the mobility by a factor of 1.6 at interwell distance of 50Å with donor and acceptor concentrations of 5 × 10 12 cm −2 and 5 × 10 13 cm −2 compared with a single delta-doped well without p-type barriers is found. This improvement in mobility could be attributed to a better confinement of carriers, which favors excited levels with nodes in the donor plane. This trade-off between carrier concentration and mobility could be exploited in high-speed, high-power and high-frequency applications.

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Influence of doping density on electronic transport in degenerate Si:Pδ-doped layers

Cited by 67 publications

References 26 publications

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

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

Electron Subband Structure and Mobility Trends in P-N Delta-Doped Quantum Wells in Si

Enhancement of the Electronic Confinement Improves the Mobility in P-N-P Delta-Doped Quantum Wells in Si

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