Vertically self-organized Ge/Si(001) quantum dots in multilayer structures

Thanh, V. Le; Yam, V.; Boucaud, P.; Fortuna, F.; Ulysse, C.; Bouchier, D.; Vervoort, Louis; Lourtioz, Jean‐Michel

doi:10.1103/physrevb.60.5851

Cited by 141 publications

(86 citation statements)

References 17 publications

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“…(15) we know that new-state elastic field u n α,i | k also follows the same equation, with the same solution forms (11) and (12), and so does the unknown elastic field u α,k | k of the new layer k. For the linearized boundary conditions (13) and (14), when we replaceû α,i by formula (15)…”

Section: Model and Elastic Formulationmentioning

confidence: 99%

“…For the strained/spacer multilayer structure, a remarkable phenomenon is the vertical self-organization of multisheet arrays of three-dimensional (3D) islands (quantum dots). 1,[9][10][11][12][13][14][15][16][17] The islands are vertically correlated in successive strained layers, with the increasing uniformity (including island size and density) as the number of layers increases. These low-dimensional nanostructures (such as quantum wires and quantum dots), realized through the development of multilayer film instability, exhibit novel electronic and optical properties, including the band structure, carrier transport, etc., and are of intense interests both for fundamental studies and for application to devices with enhanced optoelectronic performance.…”

Section: Introductionmentioning

confidence: 99%

“…1 Currently, two kinds of multilayers are being actively studied: (i) the alternating tensile/compressive multilayers exploited as multiple quantum wells or short-period superlattices; [2][3][4][5][6][7][8] and (ii) multisheets of coherently strained layers (or islands) alternately separated by spacer layers of substrate materials (strained/spacer arrays). 1,[9][10][11][12][13][14][15][16][17][18] Experimentally, these multilayer structures are grown coherently on the substrates, without the generation of undesirable misfit dislocations. When instability occurs and develops during the multilayer films growth, one of the most important phenomena is the formation of self-organized nanostructures.…”

Section: Introductionmentioning

confidence: 99%

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Stress-driven instability in growing multilayer films

Huang

Desai

2003

Phys. Rev. B

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We investigate the stress-driven morphological instability of epitaxially growing multilayer films, which are coherent and dislocation-free. We construct a direct elastic analysis, from which we determine the elastic state of the system recursively in terms of that of the old states of the buried layers. In turn, we use the result for the elastic state to derive the morphological evolution equation of surface profile to first order of perturbations, with the solution explicitly expressed by the growth conditions and material parameters of all the deposited layers. We apply these results to two kinds of multilayer structures. One is the alternating tensile/compressive multilayer structure, for which we determine the effective stability properties, including the effect of varying surface mobility in different layers, its interplay with the global misfit of the multilayer film, and the influence of asymmetric structure of compressive and tensile layers on the system stability. The nature of the asymmetry properties found in stability diagrams is in agreement with experimental observations. The other multilayer structure that we study is one composed of stacked strained/spacer layers. We also calculate the kinetic critical thickness for the onset of morphological instability and obtain its reduction and saturation as number of deposited layers increases, which is consistent with recent experimental results. Compared to the single-layer film growth, the behavior of kinetic critical thickness shows deviations for upper strained layers.

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Section: Model and Elastic Formulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stress-driven instability in growing multilayer films

Huang

Desai

2003

Phys. Rev. B

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“…The general observation is that island distribution and island density depend on growth parameters such as temperature, total coverage, growth rate and time, chemical species, faceted substrates, etc. [8][9][10][14][15][16][17][18][19][20][21][22][23][24] All of these parameters influence the surface migration and implicitly the island formation.…”

Section: D Island Growth Detailsmentioning

confidence: 99%

“…3,4 However, by stacking the island layers the size and shape of islands changes. [6][7][8] The influence of this effect on the electroluminescence is not yet known. Even the influence of the island distribution on the electroluminescence of a single layer is not well known.…”

Section: Introductionmentioning

confidence: 99%

Size distribution and electroluminescence of self-assembled Ge dots

Vescan

Stoïca

Chretien

et al. 2000

Journal of Applied Physics

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In this article we study the electroluminescence of p-i-n diode structures with Ge dots consisting of coherent three-dimensional small ͑pyramids͒ and larger ͑dome͒ islands. The Ge dots are formed through strain-induced islanding. The diode structures, including one layer with Ge dots, were deposited on Si mesas with variable areas in order to study the influence of limited area deposition on self-assembling. It was observed that the reduction of deposited area improves island uniformity. The combined analysis of island distribution and electroluminescence spectra has lead to the conclusion that domes in small diodes have a smaller Si content or are less relaxed than domes in larger diodes. The diodes are found to emit up to room temperature near the optical communication wavelength of 1.3 microns.

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Midinfrared Photoconductivity in Ge/Si Self-Assembled Quantum Dots

Boucaud

Brunhes

Sauvage

et al. 2001

phys. stat. sol. (b)

Self Cite

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We have investigated midinfrared photoconductivity of Ge/Si self-assembled quantum dots. The self-assembled quantum dots were grown by ultra-high-vacuum chemical vapor deposition on Si(001). The photoresponse of the p-type device exhibits resonances in the midinfrared around 10 mm wavelength. The photocurrent resonances are associated with intraband transitions in the valence band of the quantum dots. The photocurrent is studied as a function of applied bias and of the polarization of the incoming light. Bound-to-bound and bound-to-continuum transitions are shown to contribute to the photocurrent. The photocurrent peaks are correlated with the photoluminescence of the device.Quantum well intersubband photodetectors have been successfully developed in the 90's [1]. The use of intraband transitions in quantum dots can also lead to photodetection devices operating in the midinfrared spectral range. One advantage of using quantum dots instead of quantum wells relies on an expected larger photoconductive gain associated with a reduced capture probability. Another advantage is related to the nonvanishing normal incidence absorption which can be observed in quantum dots [2,3]. The characterization and the performances of infrared photodetectors using III-V selfassembled quantum dots have been recently reported [4][5][6][7]. Quantum dot infrared photodetectors can also be realized with Ge/Si self-assembled quantum dots. Midinfrared in-plane polarized and z-polarized intraband absorption has been recently evidenced in the valence band of Ge/Si self-assembled quantum dots [8,9]. The main advantage of Si-based photodetectors is their compatibility with C-MOS readout circuitry and the achievement of monolithic integration of the photodetectors with Si-based electronics. First measurements of midinfrared photoconductivity have been reported for Ge/Si quantum dots grown by molecular beam epitaxy [10,11].In this paper, we report on the midinfrared photocurrent spectroscopy of Ge/Si selfassembled quantum dots. The self-assembled quantum dots were grown on Si(001) substrates by ultra-high-vacuum chemical vapor deposition using silane and germane as gas precursors [12]. The growth temperature was 600 C and the gas pressure around 5 Â 10 --4 Torr during epitaxial growth. The active region consists of ten Ge quantum dot layers separated by 31 nm thick Si barriers. The active region was embedded be-1 ) Corresponding author; Phone: 33 1 69 15 40 92; Fax: 33 1 69 15 40 90;

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Vertically self-organized Ge/Si(001) quantum dots in multilayer structures

Cited by 141 publications

References 17 publications

Stress-driven instability in growing multilayer films

Stress-driven instability in growing multilayer films

Size distribution and electroluminescence of self-assembled Ge dots

Midinfrared Photoconductivity in Ge/Si Self-Assembled Quantum Dots

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