Low-frequency noise in quantum point contacts

Abstract

The kinetics of electron transport in quantum point contacts has been studied by means of low-frequency noise spectroscopy. The temperature and frequency (Lorentzian or l / f ) dependences of the noise intensity are found to be device specific, in contrast to the conductance dependence, which universally exhibits a strong quantum size effect at low temperatures. The origin of the Lorentzian noise spectrum is electron trapping and release at a single trap close to the point contact, and is connected to random resistance switching in the time domain, The l / f noise in other point contacts is attributed to a collection of traps in the vicinity of the point contact. A comprehensive model is presented which accounts for the conductance and temperature dependences of the noise in quantum point contacts.

InSituReduction of Charge Noise inGaAs/AlxGa1−xBuizert1, Koppens2, Pioro‐Ladrière3 et al. 2008Phys. Rev. Lett.8651012View full textAdd to dashboardCite

“…Charge noise has been studied both locally by monitoring conductance fluctuations in a quantum point contact (QPC) or quantum dot [7,8,9,10,11,12,13,14,15,16], and on a macroscopic scale using resistance fluctuations in Hall bar structures [16,17,18]. Several charge switching sites have been proposed, either near the 2DEG [9,10,11] or in the remote impurity layer [8,16,17] and more specifically the DX centers [13].…”

“…Several charge switching sites have been proposed, either near the 2DEG [9,10,11] or in the remote impurity layer [8,16,17] and more specifically the DX centers [13]. The charge switching process has been attributed to electron hopping between trap and 2DEG [9,10,11], electrons leaking from the split gates through the Schottky barrier [12,15] or (thermally activated) switching between different sites or configurations within the impurity layer [8,13,16,17]. Trapping of 2DEG carriers can be excluded as the dominant mechanism since 2DEG density fluctuations are too small [16,17].…”

High-resolution error detection in the capture process of a single-electron pump

“…21 The noise spectrum of I QPC in the amplifier bandwidth was dominated by a 1/f contribution, as seen in previous studies on similar QPC devices where the 1/f noise was shown to be due to an ensemble of two-level fluctuators (TLFs). 18 As discussed later, discrete time-domain jumps in I QPC due to the action of single TLFs 18,22 were also occasionally seen. To ensure high detection fidelity in the presence of the constant 1/f noise spectrum, we reference the QPC current (I N / ÀN for small N) to a second current I Z .…”

“…Electrons can be loaded with fast voltage waveforms, as used in high-speed pumping experiments 5,8 and then probed on millisecond time-scales required for high-fidelity readout. We use a 2-stage measurement protocol to suppress the effect of 1/f noise in the QPC due to non-equilibrium charged defects, 18 and we achieve a sufficiently high charge detection fidelity (probability of the charge detection yielding the right answer for N), to probe loading probabilities at the 10 À6 level. Finally, we demonstrate good qualitative agreement between electron-detection measurements of N, and hni extracted from the pumped current measured in a separate experiment.…”

Charge noise analysis of an AlGaAs/GaAs quantum dot using transmission-type radio-frequency single-electron transistor technique

“…The RTS noise has been studied in sub-micrometer Si metal-oxide-semiconductor structures [15], AlGaAs/GaAs narrow channels [16], and quantum dots [17]. A higher sample resistance in general restricts the lower frequency range that can be measured.…”