Working principles of doping-well structures for high-mobility two-dimensional electron systems

Chung, Yoon Jang; Rosales, K. A. Villegas; Baldwin, K. W.; West, K. W.; Shayegan, M.; Pfeiffer, L. N.

doi:10.1103/physrevmaterials.4.044003

Cited by 24 publications

(13 citation statements)

References 33 publications

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“…1) [3]. The Si δ -doping in the thin GaAs layer provides mobile electrons not only in the QW 75nm away but also in the neighboring AlAs layers [2][3][4][5]15]. The mobile electrons in the AlAs layers provide screening of the disorder potential created by the ionized Si donors.…”

Section: A Sample Characterizationmentioning

confidence: 99%

“…High-mobility two-dimensional electron systems (2DESs) in AlGaAs/GaAs heterostructures are the basic platform to test new concepts and study emergent phenomena in lowdimensional systems. The modulation doping technique that separates the channel and the doping layer for carrier supply [1][2][3][4][5] and advances in molecular-beam epitaxy that enable the residual impurity concentration to be decreased are the key ingredients in realizing clean 2DESs. Over the years, improvements in sample quality, manifested as higher mobility, have led to the discovery of new transport phenomena [6][7][8][9][10] and correlated phases including the fractional quantum Hall effects (FQHEs) [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, mobile electrons supplied from the donor layer accumulate not only in the GaAs quantum well (QW) several tens of nanometers away but also in the neighboring AlAs layers. The SL doping technique was later applied to ultra-highquality samples with mobility exceeding 10 × 10 6 cm 2 /Vs, where its impact on the FQHEs has been demonstrated [1][2][3][4][5]. Recently, effects of excess electrons in the SL on mobility and the quantum scattering lifetime have been studied theoretically [16,17].…”

Section: Introductionmentioning

confidence: 99%

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Screening effects of superlattice doping on the mobility of GaAs two-dimensional electron system revealed by in-situ gate control

Akiho,

Muraki

2021

Preprint

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We investigate the screening effects of excess electrons in the doped layer on the mobility of a GaAs twodimensional electron system (2DES) with a modern architecture using short-period superlattice (SL) doping. By controlling the density of excess electrons in the SL with a top gate while keeping the 2DES density constant with a back gate, we are able to compare 2DESs with the same density but different degrees of screening using one sample. Using a field-penetration technique and circuit-model analysis, we determine the density of states and excess electron density in the SL, quantities directly linked to the screening capability. The obtained relation between mobility and excess electron density is consistent with the theory taking into account the screening by the excess electrons in the SL. The quantum lifetime determined from Shubnikov-de Haas oscillations is much lower than expected from theory and did not show a discernible change with excess electron density.

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Section: A Sample Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Screening effects of superlattice doping on the mobility of GaAs two-dimensional electron system revealed by in-situ gate control

Akiho,

Muraki

2021

Preprint

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“…Modulation doping [1] initiated the modern era of semiconductor-based high mobility two-dimensional (2D) carrier systems simply by spatially separating the dopant atoms from the carriers released by the dopants, thus suppressing the detrimental effect of impurity scattering on carrier transport. During the first 30 year period of 1978-2008, the 2D mobility in the archetypal n-GaAsbased 2D electron system increased by more than a factor 1000, from 2 × 10 4 cm 2 /V s in 1978 to 3 × 10 7 cm 2 /V s in 2008, keeping pace with the famous Moore's Law in microelectronics, through materials improvement in the molecular beam epitaxy (MBE) technique used in producing high-quality semiconductor quantum wells hosting the 2D confined carriers [2,3]. This is an astonishing materials physics accomplishment, which led to a revolution in fundamental experimental condensed matter physics, leading to the laboratory observations of fractional quantum Hall effect [4], even-denominator fractional quantum Hall effect [5], bilayer fractional quantum Hall effects [6,7], Wigner crystallization [8], and many other phenomena far too numerous to cite here.…”

Section: Introductionmentioning

confidence: 99%

Density-dependent two-dimensional optimal mobility in ultra-high-quality semiconductor quantum wells

Ahn,

Sarma

2021

Preprint

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We calculate using the Boltzmann transport theory the density dependent mobility of twodimensional (2D) electrons in GaAs, SiGe and AlAs quantum wells as well as of 2D holes in GaAs quantum wells. The goal is to precisely understand the recently reported breakthrough in achieving a record 2D mobility for electrons confined in a GaAs quantum well. Comparing our theory with the experimentally reported electron mobility in GaAs quantum wells, we conclude that the mobility is limited by unintentional background random charged impurities at an unprecedented low concentration of ∼ 10 13 cm −3 . We find that this same low level of background disorder should lead to 2D GaAs hole and 2D AlAs electron mobilities of ∼ 10 7 cm 2 /V s and ∼ 4 × 10 7 cm 2 /V s, respectively, which are much higher theoretical limits than the currently achieved experimental values in these systems. We therefore conclude that the current GaAs hole and AlAs electron systems are much dirtier than the state of the arts 2D GaAs electron systems. We present theoretical results for 2D mobility as a function of density, effective mass, quantum well width, and valley degeneracy, comparing with experimental data.

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“…w in extremely high quality 2DESs confined to modulation-doped GaAs QWs grown on GaAs (001) substrates. The QWs are flanked by 150-nm-thick Al 0.24 Ga 0.76 As barriers, and the dopants are placed in doping wells [33]. The 2DESs all have the same density n 1.1×10 11 cm −2 , in order to keep the LLM parameter fixed, and the QW widths (w ) are varied from 20 to 80 nm to change w. We designate each sample by S w , e.g., S 20 refers to the sample with a QW of width w = 20 nm.…”

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confidence: 99%

Fractional quantum Hall effect energy gap: role of electron layer thickness

Rosales,

Madathil,

Chung

et al. 2021

Preprint

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The fractional quantum Hall effect (FQHE) stands as a quintessential manifestation of an interacting two-dimensional electron system. One of FQHE's most fundamental characteristics is the energy gap separating the incompressible ground state from its excitations. Yet, despite nearly four decades of investigations, a quantitative agreement between the theoretically calculated and experimentally measured energy gaps is lacking. Here we report a quantitative comparison between the measured energy gaps and the available theoretical calculations that take into account the role of finite layer thickness and Landau level mixing. Our systematic experimental study of the FQHE energy gaps uses very high-quality two-dimensional electron systems confined to GaAs quantum wells with varying well widths. All the measured energy gaps fall bellow the calculations, but as the electron layer thickness increases, the results of experiments and calculations come closer. Accounting for the role of disorder in a phenomenological manner, we find the measured energy gaps to be in reasonable quantitative agreement with calculations, although some discrepancies remain.

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Working principles of doping-well structures for high-mobility two-dimensional electron systems

Cited by 24 publications

References 33 publications

Screening effects of superlattice doping on the mobility of GaAs two-dimensional electron system revealed by in-situ gate control

Screening effects of superlattice doping on the mobility of GaAs two-dimensional electron system revealed by in-situ gate control

Density-dependent two-dimensional optimal mobility in ultra-high-quality semiconductor quantum wells

Fractional quantum Hall effect energy gap: role of electron layer thickness

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