Electronic and optical fine structure of GaAs nanocrystals: The role of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi></mml:math>orbitals in a tight-binding approach

Díaz, J. G.; Bryant, Garnett W.

doi:10.1103/physrevb.73.075329

Cited by 33 publications

(25 citation statements)

References 30 publications

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“…[27][28][29] As expected, the calculations show that there are multiple low-energy hole states localized within the CdSe cores, regardless of core size. For electrons, by contrast, there is at most one lowest-energy state localized in the core, as shown in Figure 4.…”

Section: Electronic Structure Calculationsmentioning

confidence: 61%

“…We minimized the strain energy by relaxing the lattice using the valence-force-field method. 27,34,35 In this method, the atoms in the core and shell are allowed to move in any direction in order to achieve strain relaxation at the interfaces. Minimization of the strain energy was performed using a combination of steepest-descent and conjugate-gradient techniques.…”

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confidence: 99%

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Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

et al. 2013

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It is commonly assumed that, after an electron-hole pair is created in a semiconductor by absorption of a photon, the electron and hole rapidly relax to their respective lowest-energy states before recombining with one another. In semiconductor heterostructure nanocrystals, however, intraband relaxation can be inhibited to the point where recombination occurs primarily from an excited state. We demonstrate this effect using time-resolved optical measurements of CdSe/CdS core/shell nanorods. For nanorods with large CdSe cores, an electron photoexcited into the lowest-energy state in the core remains in the core, and an electron photoexcited into an excited state in the CdS shell remains in the shell, until the electron recombines with the hole. This provides a means of controlling the spatial location of photoexcited electrons by excitation energy. The control over electron localization is explained in terms of slow relaxation into the lowest-energy electron state in the nanorods, on time scales slower than electron-hole recombination. The observation of inhibited relaxation suggests that a simple picture of band alignment is insufficient for understanding charge separation in semiconductor heterostructures.

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Section: Electronic Structure Calculationsmentioning

confidence: 61%

mentioning

confidence: 99%

Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

et al. 2013

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“…The electronic structure of semiconductor nanocrystals has been previously investigated using a variety of theoretical approaches: (i) effective mass models and k · p methods 38-41 , often provide analytical solutions which are easier and more intuitive to understand than the numerical results of atomistic methods, such as (ii) the tight-binding method [42][43][44][45][46][47] , (iii) the semi-empirical pseudo-potential method, 48,49 , and (iv) fully self-consistent ab-initio methods, based on density functional theory [50][51][52][53][54][55][56][57] .…”

Section: Methodsmentioning

confidence: 99%

Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures

Sills

Califano

2015

Phys. Chem. Chem. Phys.

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Nanorod solar cells have been attracting a lot of attention recently, as they have been shown to exhibit a lower carrier multiplication onset and a higher quantum efficiency than quantum dots with similar bandgaps. The underpinning theory for this phenomenon is not yet completely understood, and is still the subject of ongoing study. Here we conduct a theoretical investigation into CM efficiency in elongated semiconductor nanostructures with square cross section made of different materials (GaAs, GaSb, InAs, InP, InSb, CdSe, Ge, Si and PbSe), using a single-band effective mass model. Following Luo, Franceschetti and Zunger we adopt the CM figure of merit (the ratio between biexciton and single-exciton density of states) as a measure of CM efficiency and investigate its dependence on the aspect ratio for both (a) constant cross section (i.e. varying the volume) and (b) constant volume (i.e., varying the cross section), by decoupling electronic structure effects from surface-related effects, increased absorption and Coulomb coupling effects. The results show that in both (a) and (b) cases elongation causes an increase in both single-and bi-exciton density of states, with the latter, however, growing much faster with increasing energy. This leads to the availability of more bi-exciton states than single-exciton states for photon energies just above the bi-exciton ground state and therefore suggests a higher probability of CM at these energies for elongated structures. Our results therefore show that the origin of the observed decrease of the CM threshold in elongated structures can be attributed purely to electronic structure effects, paving the way to the implementation of CM-efficiency-boosting strategies in nanostructures based on the lowering of the CM onset.

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“…These parametrizations demonstrate that the inclusion of d orbitals into the basis allows to obtain much better fits of the masses and energy gaps to the target material values. In particular, the treatment of the conduction band edge is significantly improved, which is particularly important for small nanostructures [34].…”

Section: The Spmentioning

confidence: 99%

Building semiconductor nanostructures atom by atom

Korkusiński

Hawrylak

Zieliński

et al. 2008

Microelectronics Journal

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Electronic and optical fine structure of GaAs nanocrystals: The role ofdorbitals in a tight-binding approach

Cited by 33 publications

References 30 publications

Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods

Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures

Building semiconductor nanostructures atom by atom

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