The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties

Usman, Muhammad; Tasco, V.; Todaro, M. T.; Giorgi, Milena De; O’Reilly, Eoin P.; Klimeck, Gerhard; Passaseo, A.

doi:10.1088/0957-4484/23/16/165202

Cited by 26 publications

(31 citation statements)

References 44 publications

(100 reference statements)

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“…The present analysis starts from our recent study [14], where we described the dependence of the polarization-dependent optical emission on the actual chemical composition of QDs for a single QD layer, as modulated by atomic scale phenomena occurring during overgrowth, i.e. In-Ga intermixing, strain-enhanced diffusion, and In segregation.…”

Section: Resultsmentioning

confidence: 99%

“…Since any tentative to simulate the overall optical response of the structure by considering QD with uniform composition, failed to explain the experimental measurements [14], the expected In/Ga intermixing effect is mimicked by using the two-composition model with a high In composition QD core surrounded by a lower In composition shell. We assigned different compositions to each region of the QDs as shown by the schematic of As a second step, we introduced a composition gradient also in the inner core of QDs, while keeping the outer shell composition gradient of 0.1.…”

Section: Theoretical Modelling Of Electronic and Optical Properties Omentioning

confidence: 99%

“…We recently demonstrated how the actual single layer QD composition profile is relevant in determining real optical behaviour of these InAs-based nanostructures [14]. This, in turn, is determined by complex nanoscale phenomena such as In-Ga intermixing and atomic segregation occurring during overgrowth with GaAs.…”

Section: Introductionmentioning

confidence: 99%

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Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Tasco

Usman²,

Giorgi

et al. 2014

Nanotechnology

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Abstract:Tailoring electronic and optical properties of self-assembled InAs quantum dots (QDs) is a critical limit for the design of several QD-based optoelectronic devices operating in the telecom frequency range. We describe how a fine control of the strain-induced surface kinetics during the growth of vertically-stacked multiple layers of QDs allow to engineer their self organization process. Most noticeably, the present study shows that the underlying strain field induced along a QD stack can be modulated and controlled by time-dependent intermixing and segregation effects occurring after capping with GaAs spacer. This leads to a drastic increase of TM/TE polarization ratio of emitted light, not accessible from the conventional growth parameters. Our detailed experimental measurements supported by comprehensive multi-million atom simulations of strain, electronic, and optical properties, provide in-depth analysis of the grown QD samples leading us to depict a clear picture on atomic scale phenomena affecting the proposed growth dynamics and consequent QD polarization response.

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Section: Resultsmentioning

confidence: 99%

Section: Theoretical Modelling Of Electronic and Optical Properties Omentioning

confidence: 99%

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Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Tasco

Usman²,

Giorgi

et al. 2014

Nanotechnology

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“…The tight-binding model is implemented with in the framework of atomistic tool NanoElectronic Modeling (NEMO 3-D) simulator [66] which has, in the past, shown an unprecedented accuracy to match experiments for the study of nanomaterials [22,31,67] and devices [47,68]. Supplementary Fig.…”

Section: Methodsmentioning

confidence: 99%

Towards low-loss telecom-wavelength photonic devices by designing GaBi_xAs_1−x/GaAs core–shell nanowires

Usman

2019

Nanoscale

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Nanowires are versatile nanostructures, which allow an exquisite control over bandgap energies and charge carrier dynamics making them highly attractive as building blocks for a broad range of photonic devices. For optimal solutions concerning device performance and cost, a crucial element is the selection of a suitable material system which could enable a large wavelength tunability, strong light interaction and simple integration with the mainstream silicon technologies. The emerging GaBi x As 1−x alloys offer such promising features and may lead to a new era of technologies. Here, we apply million-atom atomistic simulations to design GaBi x As 1−x /GaAs core−shell nanowires suitable for low-loss telecom-wavelength photonic devices. The effects of internal strain, Bi Composition (x), random alloy configuration, and core-to-shell diameter ratio (ρ D ) are analysed and delineated by systematically varying these attributes and studying their impact on the absorption wavelength and charge carrier confinement. The complex interplay between x and ρ D results in two distinct pathways to accomplish 1.55 µm optical transitions: either fabricate nanowires with ρ D ≥ 0.8 and x ∼15%, or increase x to ∼30% with ρ D ≤ 0.4. Upon further analysis of the electron hole wave functions, inhomogeneous broadening and optical transition strengths, the nanowires with ρ D ≤ 0.4 are unveiled to render favourable properties for the design of photonic devices. Another important outcome of our study is to demonstrate the possibility of modulating the strain character from a compressive to a tensile regime by simply engineering the thickness of the core region. The availability of such a straightforward knob for strain manipulation without requiring any external stressor component or Bi composition engineering would be desirable for devices involving polarisation-sensitive light interactions. The presented results document novel characteristics of the GaBi x As 1−x /GaAs nanowires with the possibility of myriad applications in nanoelectronic and nanophotonic technologies.Semiconductor nanowires made up of III-V alloys are a topic of great interest for fundamental research as they form a promising system with highly tunable electronic and optical characteristics through engineering of their geometry parameters and composition [1,2]. In terms of applications, they are an excellent absorber and emitter of light, and provide viable pathways for carrier collection and transport. The advances in the fabrication techniques for nanowires have opened possibilities for growth on silicon substrates, which offers rich opportunities for novel integrated nanoeletronic and nanophotonic technologies including photodetectors, waveguides, light-emitting diodes (LEDs), lasers, solar cells and light-sensors [3][4][5][6][7][8]. Furthermore, there have been cross-disciplinary proposals to design nanowires for novel applications such as cell imaging and solar to fuel conversion [9]. Consequently, there is an immense research interest in designing semiconductor na...

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“…(2). The discrete spectrum is convolved with a 10 meV Lorentzian broadening function and plotted in Fig.…”

Section: Optical Propertiesmentioning

confidence: 99%

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

Neupane

Rahman

Lake

2015

Phys. Chem. Chem. Phys.

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The effects of strain and confinement on the energy levels and emission spectra of dome-shaped, Ge-core-Si-shell nanocrystals (NCs) with diameters ranging from 5 to 45 nm are investigated with atomistic models. For NCs with base diameters ≥15 nm, the strain-induced increase in the energy gap is ∼100 meV. The increase in the energy gap is primarily the result of the downward shift in the occupied states confined in the Ge core. The fundamental energy gap varies from 960 meV to 550 meV as the NC diameter increases from 5 nm to 45 nm. Confinement and strain break the degeneracy of the lowest excited state and split it into two states separated by a few meV. For the smaller NCs, one of these states can be localized in the Si core and the other state can be in the Si cap. For diameters ≥20 nm, both of these states are localized in the Si cap. The electronic states are calculated using an atomistic sp(3)d(5)s* tight-binding model including spin-orbit coupling, and geometry relaxation is performed using a valence force field model.

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The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties

Cited by 26 publications

References 44 publications

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Towards low-loss telecom-wavelength photonic devices by designing GaBi_xAs_1−x/GaAs core–shell nanowires

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

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The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties

Cited by 26 publications

References 44 publications

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

Towards low-loss telecom-wavelength photonic devices by designing GaBixAs1−x/GaAs core–shell nanowires

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

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Towards low-loss telecom-wavelength photonic devices by designing GaBi_xAs_1−x/GaAs core–shell nanowires