Screening Breakdown on the Route toward the Metal-Insulator Transition in Modulation Doped Si<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>/</mml:mi></mml:math>SiGe Quantum Wells

Wilamowski, Ż.; Sandersfeld, N.; Jantsch, W.; Többen, D.; Schäffler, F.

doi:10.1103/physrevlett.87.026401

Cited by 57 publications

(31 citation statements)

References 26 publications

(28 reference statements)

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“…Previous experimental studies also reported similar exponents. 24,25 Low-density corrections to the RPA method have been suggested to explain this stronger dependence of the mobility upon the density. Indeed, if one goes beyond the TABLE I. Extracted power-law exponents α for heterostructures with different 2DEG depth in the lower and higher density regimes, along with Dingle ratios.…”

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confidence: 99%

“…A common approach to experimentally determine the dominant scattering mechanisms in two-dimensional systems is to extract the power-law exponent from the density dependence of the mobility. Several experimental and theoretical studies have used similar techniques to analyze disorder in GaAs/AlGaAs structures, [15][16][17][18][19][20][21] Si MOSFETs, 22 and doped 4,[23][24][25] and undoped [26][27][28] Si/SiGe heterostructures. With this in mind, we present in this work a systematic study of the depth dependence of scattering mechanisms in undoped shallow Si/SiGe quantum wells with channel depth ranging from 100 nm to only 10 nm away from the surface, the shallowest Si/SiGe device reported to date.…”

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confidence: 99%

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Scattering mechanisms in shallow undoped Si/SiGe quantum wells

et al. 2015

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We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

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confidence: 99%

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confidence: 99%

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

et al. 2015

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“…A large amplitude of the signal and a strong dependence of the amplitude on the position in the resonance cavity (optimized for measurements of magnetic dipole transitions) suggests the microwave electric field-driven cyclotron resonance. Cyclotron resonance-related lines are commonly detected in ESR cavities both in bulk materials 24 as well as in 2D systems like Si/SiGe quantum wells 25 or GaN/AlGaN heterostructures. 19 We should mention here that the signal did not show any signs of aging within a time scale of a month.…”

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Landau-Level Spectroscopy of Relativistic Fermions with Low Fermi Velocity in theBi2Te3Three-Dimensional Topological Insulator

et al. 2012

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ABSTRACT:X-band microwave spectroscopy is applied to study the cyclotron resonance in Bi 2 Te 3 exposed to ambient conditions. With its help, intraband transitions between Landau levels of relativistic fermions are observed. The Fermi velocity equals to 3260 m/s, which is much lower than has been reported in the literature for samples cleaved in vacuum. Simultaneous observation of bulk Shubnikov Keywords: topological insulators, cyclotron resonance, relativistic fermions.In the last five years a new class of topological quantum states has emerged, referred to as topological insulators. 1,2,3,4,5,6,7,8,9,10 Topological properties of the family of bismuth compound crystals, i.e. Bi 2 Te 3 , 5 Bi 2 Se 3 , 8 and Bi 2 Te 2 Se, 9 have been confirmed in spectacular angle resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy and spectroscopy 11 experiments. Other experiments, including electric transport or optical measurements, are difficult to perform because of high bulk conductance due to native crystal lattice defects. 6,8,12 The defects responsible for a high bulk carrier concentration are most probably Bi antisites in Bi 2 Te 3 leading to typically highly metallic ptype, and Se vacancies in Bi 2 Se 3 giving n-type conductivity. 6,13,14 In order to suppress the contribution of the conducting bulk states and expose the surface states in the experiment, very thin samples with 2 the thickness of a few quintet layers are typically studied. 15,16 An alternative approach is to use surface sensitive experimental techniques or techniques disregarding the metallic bulk. One of them is the already mentioned ARPES, which probes surface regions from a few up to tens of nm. In this communication we describe the results of microwave spectroscopy measurements performed in an Xband (9.5 GHz) resonator. The microwave penetration depth in the applied experimental conditions ranges from 4 μm to 40 μm. The technique can actually probe independently both bulk and surface properties, being partly insensitive to the detrimental influence of the metallic bulk conductivity.Similar approach has been recently applied to study surface states in Bi 2 Se 3 topological insulator, where 2D cyclotron resonance has been revealed thanks to the application of the microwave cavity transmission technique. 17 The Bi 2 Te 3 crystal was grown by the vertical Bridgman method, with an excess of tellurium in the melt in order to suppress the formation of Bi antisite defects. Growth details have been described in Ref. 18. Segregation effects, characteristic of the Bridgman method, caused the gradient of stoichiometry along the crystal growth direction. For a given temperature, the equilibrium composition of the liquid phase is typically different than of the solid phase. In the case of Bi 2 Te 3 , this causes enrichment of the liquid phase in tellurium during the growth process, and formation of the concentration gradient of defects related to tellurium excess. The crystal, highly p-type at the crystal seed due to large concentration ...

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“…In our experiment, the cyclotron resonance (CR) of the electrons in the quantum well is also observed [4,5]. From the CR signal the carrier concentration and the electron mobility can be estimated.…”

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confidence: 92%

Limitations in the Tunability of the Spin Resonance of 2D Electrons in Si by an Electric Current

et al. 2007

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We analyse the recently observed effect of an in-plane electric current through a Si quantum well on the conduction electron spin resonance. We find that the ratio of resonance shift and current density is independent of temperature and dissipation processes, but the channel current is reduced due to a parallel electric channel in heavily modulation doped samples. The inhomogeneous current distribution results in some broadening of the ESR line width. In high mobility Si/SiGe layers the current induced increase in the electron temperature is considerably larger than the increase in the lattice temperature. The signal amplitude scales with the square of electron mobility.

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Screening Breakdown on the Route toward the Metal-Insulator Transition in Modulation Doped Si/SiGe Quantum Wells

Cited by 57 publications

References 26 publications

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

Landau-Level Spectroscopy of Relativistic Fermions with Low Fermi Velocity in theBi2Te3Three-Dimensional Topological Insulator

Limitations in the Tunability of the Spin Resonance of 2D Electrons in Si by an Electric Current

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