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Abstreiter, G.; Brugger, H.; Wolf, Thomas; Jorke, H.; Herzog, H.‐J.

doi:10.1103/physrevlett.54.2441

Cited by 502 publications

(86 citation statements)

References 16 publications

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“…Over the past three decades, advances in epitaxial growth and a better understanding of scattering mechanisms have led to a tremendous mobility enhancement in Si/Si x Ge 1−x two-dimensional electron gases (2DEGs). The implementation of Ge-graded buffer layers, 1 the use of thicker buffers and spacers, 2,3 and the optimization of the channel thickness and of the Ge content of the buffer layer 4 have resulted in an increase of doped Si/SiGe electron mobilities from ∼ 2 × 10 3 cm 2 /(V · s) at 2 K and a density of ∼ 3 × 10 12 cm −2 in 1985 5 to ∼ 5 × 10 5 cm 2 /(V · s) at 0.35 K and a density of ∼ 7 × 10 11 cm −2 in 1995. 4 The development of atomic-layer-deposited (ALD) Al 2 O 3 allowed for the fabrication of undoped heterostructure field-effect transistors (HFET) 6 in which the mobility of Si/SiGe quantum wells was further improved to ∼ 2 × 10 6 cm 2 /(V · s) at 0.3 K and a density of ∼ 1.4 × 10 11 cm −2 .…”

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confidence: 99%

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

et al. 2015

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We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

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confidence: 99%

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

et al. 2015

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“…But dimensions have become so small that improvements are much harder to achieve at the rate we have become accustomed. in the 1980s [59] and has led to commercial devices [60].…”

Section: Germanium Speeds Up Transistorsmentioning

confidence: 99%

Germanium: From its discovery to SiGe devices

Häller

2006

Materials Science in Semiconductor Processing

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Germanium, element #32, was discovered in 1886 by Clemens Winkler. Its first broad application was in the form of point contact Schottky diodes for radar reception during WWII. The addition of a closely spaced second contact led to the first all-solid-state electronic amplifier device, the transistor. The relatively low bandgap, the lack of a stable oxide and large surface state densities relegated germanium to the number 2 position behind silicon. The discovery of the lithium drift process, which made possible the formation of p-i-n diodes with fully depletable i-regions several centimeters thick, led germanium to new prominence as the premier gamma-ray detector. The development of ultra-pure germanium yielded highly stable detectors which have remained unsurpassed in their performance. New acceptors and donors were discovered and the electrically active role of hydrogen was clearly established several years before similar findings in silicon. Lightly doped germanium has found applications as far infrared detectors and heavily Neutron Transmutation Doped (NTD) germanium is used in thermistor devices operating at a few milliKelvin. Recently germanium has been rediscovered by the silicon device community because of its superior electron and hole mobility and its ability to 2 induce strains when alloyed with silicon. Germanium is again a mainstream electronic material.

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“…Each type of strain influences the performance in a different way, because each has a different effect on Si band structure. Both uniaxial and biaxial strain break the 12-fold symmetry of the unstrained Si band structure (6). For biaxially strained Si, the mobility enhancement originates from scattering reduction.…”

Section: Introductionmentioning

confidence: 99%

Probing the Strain States in Nanopatterned Strained SOI

et al. 2009

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Using strained SOI as a strategy to enhance the performance of Sibased electronic devices raises fundamental questions about the stability of the strain during different processing steps. In this work, we elucidate the influence of nanoscale pattering, a crucial step in device fabrication, on the strain states. UV micro-Raman and high resolution transmission electron microscopy were employed to quantify the strain in the strained layers. Post-patterning strain in different nanostructures was evaluated by UV micro-Raman. Our data demonstrate that the formation of free surfaces upon pattering leads to a partial relaxation of the strain. The extent of the relaxation was found to depend on the lateral dimension and the geometry. A detailed mechanistic picture is presented based on 3D finite element simulations.

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Strain-Induced Two-Dimensional Electron Gas in Selectively DopedSi/SixGe1−x

Cited by 502 publications

References 16 publications

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

Germanium: From its discovery to SiGe devices

Probing the Strain States in Nanopatterned Strained SOI

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