Effect of the surface on the electronic properties of a two-dimensional electron gas as measured by the quantum Hall effect

Kopnov, G.; Umansky, V.; Cohen, Hagai; Shahar, D.; Naaman, Ron

doi:10.1103/physrevb.81.045316

Cited by 8 publications

(11 citation statements)

References 33 publications

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“…Frequently, the surfaces of semiconductor devices are passivated in order to stabilize their chemical nature and to eliminate reactivity. (NH 4 ) 2 S x [1], Si [2] and organic self-assemble monolayer (SAM) [3] have been used for coating GaAs-based devices. The effect of the surface on the electronic properties of a 2DEG has been studied by classic and quantum Hall effect measurements [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…(NH 4 ) 2 S x [1], Si [2] and organic self-assemble monolayer (SAM) [3] have been used for coating GaAs-based devices. The effect of the surface on the electronic properties of a 2DEG has been studied by classic and quantum Hall effect measurements [3,4]. Specifically, the relationship between the surface and internal electric fields with electron mobility is the most important, but this option is not the best one because the structure has to be perturbed with the electrical contacts.…”

Section: Introductionmentioning

confidence: 99%

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Determination of surface electric potential by photoreflectance spectroscopy of HEMT heterostructures

Zamora‐Peredo

Cortes-Mestizo

García-González

et al. 2013

Journal of Crystal Growth

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Determination of surface electric potential by photoreflectance spectroscopy of HEMT heterostructures

Zamora‐Peredo

Cortes-Mestizo

García-González

et al. 2013

Journal of Crystal Growth

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“…However, shallow 2DEG depths (as little as 20 nm below the surface) come at the expense of mobility. [4][5][6][7][8][9][10][11][12][13][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.…”

mentioning

confidence: 99%

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

Mak

Sfigakis

Gupta

et al. 2013

Applied Physics Letters

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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...

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“…In order to eliminate chemical instability that may cause undesired effects it is well established that the surfaces of semiconductor-based devices have to be treated properly. Frequently, the surfaces of semiconductor devices are passivated in order to stabilize their chemical nature and to eliminate reactivity [1][2][3][4]. In the AlGaAs/GaAsheterostructures case, is possible to study the effect of the surface on the electronic properties of a 2DEG by electrical measurements [3,4], inspecific the relationship between the surface electric field and the electron mobility.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Surface on Optical properties of AlGaAs/GaAs heterostructures with double 2-DEG

et al. 2013

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In this work we studied a set of heterostructuresAlGaAs/GaAs by photoreflectance (PR) and photoluminescence (PL) spectroscopy in order to determine the effect of the surface on optical properties of a symmetric double two-dimensional electron gas(2DEG). The potential profiles of the edge of the conduction band were modeled by nextnano software. By Hall effect measurements at 77K we determined the electron mobility of the samples. Thesurface electric field was calculated by the analysis Franz-Keldysh oscillations observed in thePR spectra.Thecalculation of the band structure shows that the surface electric field prevents the creation of 2DEG closest to the surface. PL spectra shows a peak originated in thedeepest AlGaAs layer, close to the 2DEG region,associated with to the free exciton whose intensity increases as the electric field decrease.

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Effect of the surface on the electronic properties of a two-dimensional electron gas as measured by the quantum Hall effect

Cited by 8 publications

References 33 publications

Determination of surface electric potential by photoreflectance spectroscopy of HEMT heterostructures

Determination of surface electric potential by photoreflectance spectroscopy of HEMT heterostructures

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

Effect of the Surface on Optical properties of AlGaAs/GaAs heterostructures with double 2-DEG

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