Si:SiGe quantum wells grown on (118) substrates: Surface morphology and transport properties

Thornton, Trevor; Fernández, Juan Manuel; Kaya, S.; Green, P. W.; Fobelets, Kristel

doi:10.1063/1.118526

Cited by 12 publications

(6 citation statements)

References 13 publications

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“…Strained silicon quantum wells on tilted substrates also show interesting surface morphology as well as anisotropic transport properties. 11,12 In this article we describe recent transport measurements of modulation doped Si:SiGe quantum wells on various offcut substrates at temperatures down to 20 mK. The results are consistent with the formation of a minigap in the density of states.…”

Section: Introductionsupporting

confidence: 77%

“…11,12 For transport perpendicular to the step edges extra electron scattering reduces the mobility compared to values measured parallel to the terraces. Figure 4 shows the sheet resistance as a function of magnetic field for a 10°o ff-cut sample at a temperature of 0.4 K. The samples have standard Hall bar geometries aligned parallel and perpendicular to the step edges.…”

Section: Electron Transport On Tilted Substratesmentioning

confidence: 96%

“…However, on tilted substrates such as (11n) the situation is different. 11,12 Two of the ͕111͖ planes still intersect the surface along ͓110͔. The other two planes align at a small angle ␣/2 on either side of ͓110͔, given by cos ␣ϭ 2 cos 2 ϩsin 2 2 cos 2 ϩ3 sin 2 , ͑1͒…”

Section: Layer Structure and Surface Morphologymentioning

confidence: 98%

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Minigaps in strained silicon quantum wells on tilted substrates

Thornton

Andresen

Pivin

et al. 1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The two-dimensional electron gas formed at the inverted surface of a tilted silicon substrate shows unusual magnetotransport properties due to the presence of a minigap in the density of states. For metal–oxide–semiconductor inversion layers the strong scattering at the interface limits the mobility to values μ<10–20 000 cm2/V s. To achieve mobilities approaching 105 cm2/V s we have used strained Si:SiGe quantum wells grown on substrates tilted away from the (001) normal by 0°, 2°, 4°, 6°, and 10°. Their transport properties have been measured in the temperature range of 20–500 mK. All the samples show strong Shubnikov–de Haas oscillations. For the 2° and 4° samples the envelope of the fast oscillations is modulated by a longer period oscillation at low magnetic fields. We attribute the slow oscillation in the 2° and 4° samples to the presence of a minigap. For the 6° and 10° samples the minigap is higher than the Fermi energy and is not expected to influence the transport properties.

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Section: Introductionsupporting

confidence: 77%

Section: Electron Transport On Tilted Substratesmentioning

confidence: 96%

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Minigaps in strained silicon quantum wells on tilted substrates

Thornton

Andresen

Pivin

et al. 1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…A very peculiar surface morphology was reported in 1997 after the gas source-molecular-beam epitaxy of SiGe virtual substrates on (1 1 8) surfaces: two sets of undulations predominantly aligned at ∼7 • on each side of a [1 1 0] cleaving direction, and a third one along the perpendicular [1 −1 0] direction [29]. In order to explain this behavior, one has to keep in mind that surface undulations are due to the periodic strain field generated by the move of 60 • misfit dislocations on {1 1 1} planes.…”

Section: Surface Morphologymentioning

confidence: 99%

Epitaxial growth of Ge thick layers on nominal and 6° off Si(0 0 1); Ge surface passivation by Si

Hartmann¹,

Abbadie²,

Cherkashin³

et al. 2009

Semicond. Sci. Technol.

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We have grown various thickness Ge layers on nominal and 6 • off Si(0 0 1) substrates using a low-temperature/high-temperature strategy followed by thermal cycling. A combination of 'mounds' and a perpendicular cross-hatch were obtained on nominal surfaces. On 6 • off surfaces, three sets of lines were obtained on top of the 'mounds': one along the 1 1 0 direction perpendicular to the misorientation direction and the other two at ∼4.5 • on each side of the 1 1 0 direction parallel to the misorientation direction. The surface root mean square roughness was less than 1 nm for 2.5 μm thick nominal and 6 • off Ge layers. Those slightly tensily strained Ge layers (R ∼ 104%) were characterized by 5 × 10 7 cm −2 (as-grown layers) −10 7 cm −2 (annealed layers) threading dislocation densities, independently of the substrate orientation. We have then described the 550 • C/650 • C process used to passivate nominal Ge(0 0 1) surfaces with Si prior to gate stack deposition. An ∼5 Å thick SiGe interfacial layer is self-limitedly grown at 550 • C and then thickened at 650 • C (5 Å min −1 ) thanks to SiH 2 Cl 2 at 20 Torr. Such a Ge surface passivation yields state-of-the-art p-type metal oxide semiconductor field effect transistors provided that 15 Å Si layer thickness is not exceeded. For higher thickness, elastic strain relaxation (through the formation of numerous 2D islands) occurs, followed by plastic relaxation (for a 35 Å thick Si layer).

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“…For instance, the low-temperature mean free path in strained and tilted Si/SiGe heterostructures has long since reached the value of 0.75 lm. 36 Therefore, the practical applications of amphoteric refraction at an isotropic/ anisotropic interface are within the technological range and can be used to manipulate ballistic electron beams in miniaturized devices.…”

Section: Discussionmentioning

confidence: 99%

Steering and collimating ballistic electrons with amphoteric refraction

Radu¹,

Dragoman²,

Iftimie³

2012

Journal of Applied Physics

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We show that amphoteric refraction of ballistic electrons, i.e., positive or negative refraction depending on the incidence angle, occurs at an interface between an isotropic and an anisotropic medium and can be employed to steer and collimate electron beams. The steering angle is determined by the materials’ parameters, but the degree of collimation can be tuned in a significant range by changing the energy of ballistic electrons.

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Si:SiGe quantum wells grown on (118) substrates: Surface morphology and transport properties

Cited by 12 publications

References 13 publications

Minigaps in strained silicon quantum wells on tilted substrates

Minigaps in strained silicon quantum wells on tilted substrates

Epitaxial growth of Ge thick layers on nominal and 6° off Si(0 0 1); Ge surface passivation by Si

Steering and collimating ballistic electrons with amphoteric refraction

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