Laterally self-ordered silicon-germanium islands with optimized confinement properties

Zabel, T.; Sircar, N. R.; Hauke, N.; Zweck, Josef; Döblinger, Markus; Kaniber, M.; Finley, Jonathan J.; Abstreiter, G.; Arakawa, Yasuhiko; Bougeard, Dominique

doi:10.1063/1.4818331

Applied Physics Letters

2013

DOI: 10.1063/1.4818331

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Laterally self-ordered silicon-germanium islands with optimized confinement properties

T. Zabel

N. R. Sircar

N. Hauke

et al.

Abstract: We present an analysis of the electronic confinement properties of self-assembled islands forming via silicon and germanium co-deposition in molecular beam epitaxy. This approach allows the fabrication of laterally self-ordered three dimensional islands in the Stranski-Krastanow growth mode. Using a systematic structural analysis, we derive a realistic fit-parameter free island model for band structure simulations. A comparison between these band structure simulations and photoluminescence spectroscopy shows t… Show more

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Cited by 3 publications

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“…The foundations of such selection rules have been discussed only recently [9,10], providing a theoretical framework. Moreover, the spin-dependent mechanisms governing phononless transitions in Si-based quantum confined structures, which have been discussed in terms of enhanced optical properties compared to bulk Si [11,12], have yet to be established.…”

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Experimental investigation of the optical spin-selection rules in bulk Si and Ge/Si quantum dots

Sircar

Bougeard

2014

Phys. Rev. B

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We study the relationship between the circular polarization of photoluminescence and the magnetic-fieldinduced spin polarization of the recombining charge carriers in bulk Si and Ge/Si quantum dots. First, we quantitatively compare experimental results on the degree of circular polarization of photons resulting from phonon-assisted radiative transitions in intrinsic and doped bulk Si with calculations which we adapt from recently predicted spin-dependent phonon-assisted transition probabilities in Si. The excellent agreement of our experiments and calculations quantitatively verifies these spin-dependent transition probabilities and extends their validity to weak magnetic fields. Such magnetic fields can induce a luminescence polarization of up to 3%/T. We then investigate phononless transitions in Ge/Si quantum dots as well as in degenerately doped Si. Our experiments systematically show that the sign of the degree of circular polarization of luminescence resulting from phononless transitions is opposite to the one associated with phonon-assisted transitions in Si and with phononless transitions in direct-band-gap semiconductors. This observation implies qualitatively different spin-dependent selection rules for phononless transitions, which seem to be related to the confined character of the electron wave function. Silicon is an attractive materials platform for spin-based information-processing devices [1] due to properties favoring long spin lifetimes such as a weak hyperfine coupling [2], low spin-orbit coupling, and the absence of piezoelectricity [3,4]. For direct-band-gap semiconductors, the optical orientation of charge carrier spins by an interaction with circularly polarized light represents an important tool for the study of carrier spins [5,6]. For indirect-band-gap group IV materials, this concept has triggered recent work, highlighting, for example, the accessibility of optical spin orientation via the direct band gap in Ge [7,8]. In bulk Si, however, optical transitions relevant for spin orientation experiments involve phonon-assisted transitions across the indirect band gap. A quantitative and contact-free optical spin detection and analysis of spin dynamics in this material will depend on the knowledge of spin-dependent optical selection rules for the involved phonon-assisted transitions. The foundations of such selection rules have been discussed only recently [9,10], providing a theoretical framework. Moreover, the spin-dependent mechanisms governing phononless transitions in Si-based quantum-confined structures, which have been discussed in terms of enhanced optical properties compared to bulk Si [11,12], have yet to be established.In this contribution, we present a study on spin-dependent transition probabilities for radiative recombinations of photoexcited carriers in bulk Si and quantum-confined Ge/Si structures in photoluminescence (PL) experiments. The degree of spin polarization (DSP) of the photoexcited carriers is adjusted through static magnetic fields. To quantitatively connect the...

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Experimental investigation of the optical spin-selection rules in bulk Si and Ge/Si quantum dots

Sircar

Bougeard

2014

Phys. Rev. B

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Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

Shklyaev

Bolotov

Poborchii

et al. 2015

Journal of Applied Physics

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The formation of three-dimensional (3D) structures during Ge deposition on Si(111) at about 800 °C is studied with scanning tunneling, Kelvin probe and electron microscopies, and scanning tunneling and Raman spectroscopies. The observed surface morphology is formed by dewetting of Ge from Si(111), since it occurs mainly by means of minimization of surface and interfacial energies. The dewetting proceeds through massive Si eroding around growing 3D structures, providing them to be composed of SiGe with about a 30% Ge content, and leads to the significant reduction of the SiGe/Si interface area. It is found that the SiGe top component of 3D structures forms sharp interfaces with the underlying Si. The minimization of interfacial and strain energies occurs on the way that the 3D structures appear to get the dendrite-like shape. The Ge distribution in the 3D SiGe structures is inhomogeneous in the lateral dimension with a higher Ge concentration in their central areas and Ge segregation on their surface.

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Nucleation versus instability race in strained films

Liu

Berbézier

David

et al. 2017

Phys. Rev. Materials

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Laterally self-ordered silicon-germanium islands with optimized confinement properties

Cited by 3 publications

References 26 publications

Experimental investigation of the optical spin-selection rules in bulk Si and Ge/Si quantum dots

Experimental investigation of the optical spin-selection rules in bulk Si and Ge/Si quantum dots

Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

Nucleation versus instability race in strained films

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