High-electron-mobility Si/SiGe heterostructures: influence of the relaxed SiGe buffer layer

Schäffler, F.; Többen, D.; Herzog, H.‐J.; Abstreiter, G.; Holländer, B.

doi:10.1088/0268-1242/7/2/014

Cited by 278 publications

(94 citation statements)

References 14 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%

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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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“…All devices were measured in a 3 He cryostat at a base temperature of 300 mK using low-frequency (10-100 Hz) lock-in measurement techniques in a standard four-terminal geometry with a constant excitation current ranging from 10 to 50 nA. The HFETs operated in enhancement mode, with a positive voltage applied to the gate to induce a 2DEG.…”

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Scattering mechanisms in shallow undoped Si/SiGe quantum wells

et al. 2015

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“…An example of a quite elaborate strain and composition analysis of Si/SiGe short period superlattice sample grown on a graded buffer using a growth concept which was suggested by Schäfller et al [20] is shown in Figs. 5a and 5b.…”

Section: Relaxed Si/ge Structuresmentioning

confidence: 99%

High Resolution X-ray Reciprocal Space Mapping

Bauer

Holý

1996

Acta Phys. Pol. A

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A survey will be given on recent advances in the investigation of semiconductor epilayers, heterostructures and superlattices using reciprocal space mapping techniques based on triple-axis diffractometry. It is shown that X-ray reciprocal space mapping yields quantitative information on strain, strain relaxation, as well as composition in such structures. These data are obtained from analyses of the isointensity contours of scattered X-ray intensity around reciprocal lattice points. Further analysis of the diffuse scattering yields also information on defect distribution in the epilayers.

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“…This material system has attracted much attention for the potential opto-electronic applications [6]. Very high electron mobilities and the fractional quantum Hall effect have been observed in the strained Si layers grown between relaxed SiGe layers [7][8][9]. Ordering of the Si and Ge atoms within the alloy has been predicted [10], observed by various groups [3][4][5] and it is still subject of controversy [11].…”

Section: Introductionmentioning

confidence: 99%

Initial stages of SiGe epitaxy on Si(001) studied by scanning tunneling microscopy

Oral

Ellialtioglu

1995

Surface Science

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We have studied the initial stages of strained SiGe alloy growth on the Si(001)-(2 × 1) surface by scanning tunneling microscopy. The Si0.36Ge0.64 alloy was grown on the silicon substrate at various coverages (0.13-3.6 ML) and at different temperatures (~ 310-470°C). The growth was one dimensional, preferring the direction perpendicular to the underlying silicon dimer rows at low coverages and low temperatures. Anti-phase boundaries were observed to lead multi-layer growth. Strong interaction between the overlayer and the substrate was found to buckle the substrate as well as SiGe dimers. Different growth mechanisms, island formation and step flow, were identified at low and high substrate temperatures. (2 X n) ordering of the strained overlayer was only observed at an intermediate growth temperature (~ 390°C).

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High-electron-mobility Si/SiGe heterostructures: influence of the relaxed SiGe buffer layer

Abstract: n-type modulation-doped Si/SiGe heterostructures were grown on different types of partly relaxed SiGe buffer layers, which are required in this material system to obtain a large enough conduction band offset. The samples were characterized by

Cited by 278 publications

References 14 publications

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

High Resolution X-ray Reciprocal Space Mapping

Initial stages of SiGe epitaxy on Si(001) studied by scanning tunneling microscopy

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