Free GaAs surfaces studied using a back-gated undoped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">GaAs</mml:mi><mml:mo>/</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ga</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml

Kawaharazuka, Atsushi; Saku, T.; Kikuchi, Chihiro; Horikoshi, Y.; Hirayama, Y.

doi:10.1103/physrevb.63.245309

Cited by 21 publications

(16 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The limitations described above can be circumvented or mitigated by using undoped heterostructures in different field-effect transistor (FET) geometries such as the SISFET [18][19][20][21][22] (semiconductor-insulator-semiconductor), the MISFET 23-25 (metal-insulator-semiconductor), or the HIGFET 26 (heterostructure-insulator-gate). Since there are no intentional dopants, the 2DEG can be brought much closer to the surface without sacrificing mobility.…”

Section: -17mentioning

confidence: 99%

Ultra-shallow quantum dots in an undoped GaAs/AlGaAs two-dimensional electron gas

Mak

Sfigakis

Gupta

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

We report quantum dots fabricated on very shallow 2-dimensional electron gases, only 30 nm below the surface, in undoped GaAs/AlGaAs heterostuctures grown by molecular beam epitaxy. Due to the absence of dopants, an improvement of more than one order of magnitude in mobility (at 2×10 11 cm −2 ) with respect to doped heterostructures with similar depths is observed. These undoped wafers can easily be gated with surface metallic gates patterned by e-beam lithography, as demonstrated here from single-level transport through a quantum dot showing large charging energies (up to 1.75 meV) and excited state energies (up to 0.5 meV).Electrostatically-defined quantum dots fabricated on high-mobility GaAs/AlGaAs heterostructure have been − and continue to be − invaluable in many fundamental investigations, e.g. Kondo physics and spin-based solid-state qubits. Unfortunately, the characteristics of these devices are extremely sensitive to seemingly random charge fluctuations in their local electrostatic potential, commonly known as Random Telegraph Signal (RTS) noise, or charge noise. Although one can perform a biased cooling 1,2 or a thermal cure 3 to attempt to drastically reduce the levels of charge noise on a given device, results from both techniques vary from device to device.Quantum dots fabricated in shallow two-dimensional electron gases (2DEGs) have two advantages over their deeper cousins. First, finer features can be transferred from the surface metallic gates to the 2DEG. Second, the energy scales of the dot levels tends to be larger, which enable operation at higher temperatures. However, shallow 2DEG depths (as little as 20 nm below the surface) come at the expense of mobility.4-14 Furthermore, the dopant layer may partially screen surface gates (through hopping conduction) and/or facilitate gate leakage, rendering many such wafers ungateable by surface metallic gates. The ungateability of some doped wafers is not only restricted to shallow 2DEGs, but also can occur in high-mobility doped wafers. 15-17The limitations described above can be circumvented or mitigated by using undoped heterostructures in different field-effect transistor (FET) geometries such as the SISFET 18-22 (semiconductor-insulator-semiconductor), the MISFET 23-25 (metal-insulator-semiconductor), or the HIGFET 26 (heterostructure-insulator-gate). Since there are no intentional dopants, the 2DEG can be brought much closer to the surface without sacrificing mobility. Furthermore, undoped quantum dots would not suffer from one possible source of charge noise: electrons hopping between dopant sites in AlGaAs. In doped wafers, intentional dopants typically outnumber unintentional dopants 10,000 to 1 (depending on mobility). Finally, undoped quantum dots may also interact with fewer undesirable impurities in the vicinity and are far more reproducible upon thermal cycling than their doped counterparts.27 In this Letter, we compare ultra-shallow undoped and doped GaAs/AlGaAs 2DEGs, and demonstrate gated quantum dots on ultra-shallow undoped heter...

show abstract

Section: -17mentioning

confidence: 99%

Ultra-shallow quantum dots in an undoped GaAs/AlGaAs two-dimensional electron gas

Mak

Sfigakis

Gupta

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…The formulation of the boundary conditions to be used in this equation at the surface z ϭ0 requires assumptions about the behavior of the exposed surface region in the opening between the gates. The recent experimental results 15 for GaAs/ AlGaAs heterostructures unambiguously indicate that the frozen surface model is more appropriate at low temperatures. The first, the pinned surface model, assumes a constant potential at the surface.…”

Section: Model and Methodsmentioning

confidence: 83%

Limitations of split-gate ballistic electron waveguides

Raichev

Debray

2003

Journal of Applied Physics

View full text Add to dashboard Cite

Conductance quantization in deep mesa-etched gate-controlled ballistic electron waveguidesWe study the ballistic conductance of electron waveguides created by lateral depletion of the two-dimensional ͑2D͒ electron gas caused by negatively biased split surface Schottky gates. The maximal number of resolved steps of the quantized conductance staircase and their temperature stability are examined as functions of slit width w, depth d of the 2D layer from the surface, and 2D electron density n. Conditions to obtain a large number of well-resolved steps at high temperatures are explored and formulated. Limitations of the split-gate devices are also discussed. In particular, we find that while the increase of n and decrease of d are always desirable, the width w has to be optimized to have a maximum number of steps at a given temperature.

show abstract

“…Two-dimensional electron gas (2DEG) is induced by the back-gate bias in an undoped quantum well [1], unlike the conventional method of changing the electron density by depleting the electrons by a surface gate on Si modulation-doped quantum wells or single heterojunctions. [1,5,6] In this paper, we report measurements of PL in magnetic fields as a function of the electron density from the nominally undoped condition to 2 × 10 11 cm −2 tuned continuously by a back gate structure. High quality 2DEG in the low electron density regime have been investigated by measurements of transport properties.…”

Section: Introductionmentioning

confidence: 99%