Partially Suppressed Shot Noise in Hopping Conduction: Observation in SiGe Quantum Wells

Kuznetsov, V. V.; Méndez, E. E.; Zuo, Xu; Snider, Gregory L.; Croke, E. T.

doi:10.1103/physrevlett.85.397

Cited by 36 publications

(41 citation statements)

References 24 publications

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“…To summarize, simulations of shot noise at 2D hopping have confirmed our previous hypothesis 4) that in the absence of substantial Coulomb interaction, the Fano factor F in sufficiently large samples scales approximately inversely with L. This fact, which has also been confirmed in recent experiments with lateral transport in SiGe quantum wells 7) and GaAs MOSFET channels, 8) may have substantial implications for the design of singleelectron devices immune to random offset charges. …”

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confidence: 66%

Shot Noise at 2D Hopping

et al. 2003

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We have used modern supercomputer facilities to carry out extensive Monte Carlo simulations of 2D hopping at ultimately random distribution of localized sites in both space and energy, for negligible Coulomb interaction. The emphasis was made on the power spectrum S I (ω) and low-frequency intensity of current noise, but average dc current I, as well as r.m.s. hop lengths (both bare, r , and current-weighted r I ) were calculated as well. Keeping the same statistical parameters, all results were averaged over a large number of samples, each with a random distribution of localized sites over the sample area and energy axis.The average characteristics of hopping transport have been found to be different in three regimes, all of which are visible in Figure 1 showing the nonlinear conductivity σ as a function of the electric field E for several values of temperature T . tric field E for several values of temperature T . In order to obtain these data, dc current was averaged over 80 samples of size ranging from 6a×4a to 800a×500a. Straight line shows the best fit σ/σ 0 = 0.08 exp(−0.98(E 0 /E) 1/3 ), where σ 0 ≡ ge 2 / , g 1 is the dimensionless conductivity,and E 0 ≡ 1/ena 2 .In the low electric field regime, eE r T T 0 , the dc conductivity does not depend on E and is close to that predicted by the variable range hopping theory,, where T 0 ≈ 27/4πna 2 . In the so- * ykinkhab@grad.physics.sunysb.edu † Present address: University of California, Riverside, CA 92521-0204, U.S.A.called "high" (for us, intermediate) field regime, T eE r eE 0 r (where E 0 ≡ 1/ena 2 , a is the localization length and n the 2D density of localized states), the direction of most hops is strongly aligned with that of electric field, and nonlinear conductivity σ(E) follows the prediction, 2) σ(E) ∝ exp −B (E 0 /E) 1/3 , with B = 0.98 ± 0.05. Finally, in the "ultrahigh" field regime, (eE r 1/na 2 ) the variable-range hopping theory is not valid, and dc conductivity grows even faster with the applied field.The spectral density S I (ω) of current fluctuations has been calculated using a special advanced algorithm. 3)As expected, in the absence of Coulomb interaction the S I (ω) does not exhibit 1/f -type noise, flattening at ω → 0 (Fig.2). Thus the Fano factor F ≡ S I (0) /2eI characterizing low-frequency noise is well defined. Shot noise (i.e. current noise at low temperatures, T eE r ) always decreases with increasing sample length, L. confirming the behavior conjectured in Ref.4) Parameter

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Section: )supporting

confidence: 66%

Shot Noise at 2D Hopping

et al. 2003

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“…In long enough samples, the experiments in 2D VRH regime [11,12] find that the Fano factor decays with the sample length roughly as F ∝ L −1 . This behavior is qualitatively explained by the averaging of the Poissonian noises associated with different hops, analogous to noise averaging in a one-dimensional array of N identical tunnel junctions F = 1/N [13].…”

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confidence: 99%

“…In the VRH conduction regime, however, the hopping rates are spread exponentially wide, so that only the most resistive hops (so called hard hops) are important for the noise averaging [11,12]. A typical distance between these hard hops, known as a correlation length L C of the critical cluster [9], represents a length scale for the Fano-factor [11,12] …”

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confidence: 99%

Finite-size effect in shot noise in hopping conduction

et al. 2013

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We study a current shot noise in a macroscopic insulator based on a two-dimensional electron system in GaAs in a variable range hopping (VRH) regime. At low temperature and in a sufficiently depleted sample a shot noise close to a full Poissonian value is measured. This suggests an observation of a finite-size effect in shot noise in the VRH conduction and demonstrates a possibility of accurate quasiparticle charge measurements in the insulating regime.As first shown by Schottky for the case of a vacuum tube, electric current can be viewed as a sequence of uncorrelated pulses corresponding to arrivals of individual electrons at the anode [1]. A mean-squared current fluctuation (shot noise) in this random Poissonian process has a spectral density of S I = 2qI, where q ≡ e is the elementary charge and I is the average current. A direct shot noise measurement of the charge q of a quasiparticle is intriguing in application to various solid state materials, where q can be renormalized by interactions (q = e) [2,3]. This list includes nontrivial many-body insulating states in charge-density wave compounds [4], in cooper pair insulators [5,6] and in the bulk of a two-dimensional (2D) system in fractional quantum Hall effect [7].

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“…A wide variety of noise behaviors due to localized states in mesoscopic systems have been studied both theoretically [13][14][15][16] and experimentally. [17][18][19][20][21] On the other hand, a clear demonstration of the shot noise behavior of an ideal tunnel barrier is still missing for semiconductor systems. In this paper, we report our observation of such a behavior in semiconductor tunnel barriers under various measurement configurations.…”

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confidence: 99%

“…These results are similar to those from other groups. 17,19,20 the data requires information of the microscopic details ͑e.g., coupling between localized states and contacts͒ of the barrier. Figure 3 shows the results of similar measurements on four different barriers of the smaller size.…”

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confidence: 99%