Alignment control of self-ordered three dimensional SiGe nanodots

Yamamoto, Yuji; Itoh, Yoshinori; Zaumseil, P.; Schubert, Markus Andreas; Capellini, Giovanni; Montalenti, Francesco; Washio, Katsuyoshi; Tillack, Bernd

doi:10.1088/1361-6641/aae62d

Cited by 8 publications

(11 citation statements)

References 13 publications

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“…Ge nanodot formation on concave part) is due to surface energy reduction and dot-on-dot vertical alignment is caused by strain energy reduction. In the case of 3D SiGe nanodot formation on a rough Si surface, 10,11 the preferred position of the SiGe nanodot formation is in concave regions, because tensile strain above the embedded SiGe nanodots is not high enough. As a result, the main driving force of the SiGe nanodot formation is not strain energy reduction but surface energy reduction.…”

Section: Resultsmentioning

confidence: 99%

“…By using SiH 2 Cl 2 as precursor for the Si growth, a vertically aligned dot-on-dot structure was formed because of smooth Si spacer surface formation. 11 In this study we discuss the influence of Si surface roughness on the Ge nanodot formation and demonstrate vertical and lateral self-ordering of 3D BCT Ge nanodot formation and discuss strain distribution of each Ge nanodot and surrounding.…”

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confidence: 97%

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Self-Ordered Ge Nanodot Fabrication by Using Reduced Pressure Chemical Vapor Deposition

Yamamoto

Itoh

Zaumseil

et al. 2019

ECS J. Solid State Sci. Technol.

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Ge nanodot formation on Si surface and its three dimensional alignment is investigated using a reduced pressure chemical vapor deposition system. By exposing GeH 4 on Si (001) surface at 550°C, a smooth wetting Ge layer is deposited for the first ∼0.9 nm, and then Ge nanodot formation occurs according to a Stranski-Krastanov growth mechanism. The Ge nanodots are randomly distributed with density of ∼6 × 10 10 cm −2 . By postannealing at 600°C, the Ge nanodots are coalesced. The size and density become ∼60 nm diameter 5 nm height and ∼1.5 × 10 10 cm −2 , respectively. By exposing GeH 4 followed by postannealing at 600°C on checkerboard mesa structured Si surface which is fabricated by embedded body-centered tetragonal (BCT) Si 0.6 Ge 0.4 nanodots, the Ge nanodot formation occurs at concave regions of the checkerboard mesa. By repeating Ge nanodot formation followed by Si spacer deposition by two step epitaxy using SiH 4 at 600°C and using SiH 2 Cl 2 at 700°C, vertical alignment of the Ge nanodots is observed. The lateral periodicity of the Ge nanodots is the same as that of the BCT Si 0.6 Ge 0.4 nanodot template. The driving force of the self-ordered alignment is tensile strain of Si spacer surface above the Ge nanodots. By using the checkerboard mesa structured Si substrate by embedded BCT Si 0.6 Ge 0.4 nanodot stack deposition as a template, vertically and laterally aligned 3D Ge nanodot stack fabrication is demonstrated without photolithography process.

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Section: Resultsmentioning

confidence: 99%

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confidence: 97%

Self-Ordered Ge Nanodot Fabrication by Using Reduced Pressure Chemical Vapor Deposition

Yamamoto

Itoh

Zaumseil

et al. 2019

ECS J. Solid State Sci. Technol.

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“…For the SiGe nanodot formation we have presented vertically and laterally ordered multi-layered SiGe nanodots in Si by SiGe/Si SL deposition without pre-structuring. 19,20) By selecting SiH 4 or SiH 2 Cl 2 as a precursor for the Si spacer growth, the surface morphology can be controlled. By proactively using local tensile strain and surface energy of the Si spacer surface, it is possible to control the following SiGe nanodot formation at on-dot positions or at staggered positions.…”

Section: Introductionmentioning

confidence: 99%

Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe

Wen

Schubert

Tillack

et al. 2023

Jpn. J. Appl. Phys.

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Self-ordered multilayered Ge nanodots with SiGe spacers on Si0.4Ge0.6 virtual substrate were fabricated by using reduced-pressure chemical vapor deposition, and the mechanism of vertical ordering was investigated. Process conditions of Ge and SiGe layer deposition are H2-GeH4 at 550 °C and H2-SiH4-GeH4 at 500 °C - 550 °C, respectively. By depositing the SiGe at 550 °C or raising Ge content, the SiGe surface becomes smooth, resulting in vertically-aligned Ge nanodots to reduce strain energy. Ge nanodots prefer to grow on the nanodot where the SiGe is relatively tensile strained due to the buried Ge nanodot underneath. By depositing at 500 °C and lowering Ge content, checkerboard-like surface forms, and the following Ge nanodots grow at staggered positions to reduce surface energy. The Ge nanodots are laterally aligned along elastically soft <100> direction without pre-structuring resulting from the strain distribution.

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“…In previous works, we have reported about the cyclic annealing process, which contains several cycles of annealing by interrupting the Ge deposition steps. [16][17][18] By these Ge growth techniques, high quality Ge growth with TDD of below 1 × 10 7 cm −2 is realized on Si (001) surface. Moreover, other crystal orientation such as the Ge (111) surface is also interesting because of higher carrier mobility.…”

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confidence: 99%

High Crystallinity Ge Growth on Si (111) and Si (110) by Using Reduced Pressure Chemical Vapor Deposition

Yamamoto

Wen²,

Schubert³

et al. 2023

ECS J. Solid State Sci. Technol.

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A method for high-quality epitaxial growth of Ge on Si (111) and Si (110) was investigated by reduced pressure chemical vapor deposition. Two-step Ge epitaxy (low-temperature Ge seed and high-temperature main Ge growth) with several cycles of annealing by interrupting the Ge growth (cyclic annealing) was performed. In the case of Ge seed layer growth below 350°C for (111) orientation and 400°C for (110) orientation, huge surface roughening due to too high dislocation density is observed after the following annealing step. For both crystal orientations, a high crystallinity Ge seed layer is realized by combination of 450°C growth with 800°C annealing. Once the high-quality Ge seed layer is deposited, high crystal quality Ge can be grown at 600°C on the seed layer for both crystal orientations. For the 5 µm thick Ge layer deposited with the cyclic annealing process at 800°C, a Si diffusion length of ~400 nm from the interface, RMS roughness below 0.5 nm and threading dislocation density of 5×106 cm-2 are achieved for both (111) and (110) substrates.

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Alignment control of self-ordered three dimensional SiGe nanodots

Cited by 8 publications

References 13 publications

Self-Ordered Ge Nanodot Fabrication by Using Reduced Pressure Chemical Vapor Deposition

Self-Ordered Ge Nanodot Fabrication by Using Reduced Pressure Chemical Vapor Deposition

Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe

High Crystallinity Ge Growth on Si (111) and Si (110) by Using Reduced Pressure Chemical Vapor Deposition

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