Quantum-confinement effects in InAs–InP core–shell nanowires

Zanolli, Zeila; Pistol, Mats-Eric; Fröberg, Lars; Samuelson, Lars

doi:10.1088/0953-8984/19/29/295219

Cited by 52 publications

(68 citation statements)

References 36 publications

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“…The experimental values for wurtzite are taken from TEM measurements [1], while, for the zinc-blende, the experimental parameter measured at room temperature [29] has been extrapolated to zero degrees Kelvin. From this comparison we see that the calculated lattice constants when the d electrons are treated as valence states are very close to experimental results.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Among the technologically important III-V semiconductors, one exceptional example is InAs. Indeed InAs nanowires (NWs) grow purely in wurtzite structure with [0001] orientation when InAs (111)B is chosen as substrate [1]. Recalling that the zinc-blende structure (zb, 3C, space group F 43m (T 2 d )) is the stable phase of bulk InAs, the new hexagonal phase (wurtzite wz, 2H, space group P 6 3 mc (C 6 4v )) clearly represents a theoretical challenge.…”

Section: Introductionmentioning

confidence: 99%

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Model GW band structure ofInAsandGaAsin the wurtzite phase

et al. 2007

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We report the first quasiparticle calculations of the newly observed wurtzite polymorph of InAs and GaAs. The calculations are performed in the GW approximation using plane waves and pseudopotentials. For comparison we also report the study of the zinc-blende phase within the same approximations. In the InAs compound the In 4d electrons play a very important role: whether they are frozen in the core or not, leads either to a correct or a wrong band ordering (negative gap) within the Local Density Appproximation (LDA). We have calculated the GW band structure in both cases. In the first approach, we have estimated the correction to the pd repulsion calculated within the LDA and included this effect in the calculation of the GW corrections to the LDA spectrum. In the second case, we circumvent the negative gap problem by first using the screened exchange approximation and then calculating the GW corrections starting from the so obtained eigenvalues and eigenfunctions. This approach leads to a more realistic band-structure and was also used for GaAs. For both InAs and GaAs in the wurtzite phase we predict an increase of the quasiparticle gap with respect to the zinc-blende polytype.

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Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Model GW band structure ofInAsandGaAsin the wurtzite phase

et al. 2007

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“…Both InP and InAs have a wurtzite crystal structure in the NW form, [4][5][6] although bulk InP and InAs crystallize to a zinc-blende structure. Moreover, in our CMN sample a thin InAs layer is surrounded by thick InP layers from all sides and the InP layers act like a mold.…”

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confidence: 99%

Type-II behavior in wurtzite InP/InAs/InP core-multishell nanowires

Pal

Goto

Ikezawa

et al. 2008

Applied Physics Letters

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We study optical transitions from a periodic array of InP/InAs/InP core-multishell nanowires ͑CMNs͒ having a wurtzite crystal structure by using photoluminescence ͑PL͒ and PL excitation ͑PLE͒ spectroscopy. Observing a large Stokes shift between PL and PLE spectra, a blueshift of the PL peak with a cube-root dependence on the excitation power and a slow and nonexponential decay of PL with an effective decay time of 16 ns suggest a type-II band alignment. Band-offset calculation based on the "model-solid theory" of Van Nanometer-scale semiconductor heterostructures such as quantum dots, quantum wires, and quantum wells ͑QWs͒ have been interesting research targets due to their unique size-dependent electronic and optical properties associated with the lower dimensionality and quantum confinement effects. There have been revived interests in semiconductor nanowires ͑NWs͒ due to recent success in growth and fabrication of a regular array of core-shell and core-multishell NWs ͑CMNs͒.1,2 Semiconductor NWs can be used as building blocks of sophisticated nanoscale electronic and photonic devices.3 Much effort has been devoted so far to the growth and fabrication of CMNs and the periodic arrays of such structures.1,2 However, very little is known about the electronic structure and optical properties of this new class of technologically important structures.In this letter we report optical studies on the periodic array of InP/InAs/InP CMNs. Both InP and InAs have a wurtzite crystal structure in the NW form, 4-6 although bulk InP and InAs crystallize to a zinc-blende structure. Moreover, in our CMN sample a thin InAs layer is surrounded by thick InP layers from all sides and the InP layers act like a mold. As a first approximation, we may consider that the InAs lattice experiences a three-dimensional compressive strain and attains the size of the InP lattice in all directions unlike InAs/InP QWs, where the InAs lattice is compressed in the crystal growth plane and is elongated in the growth direction. There have been a few studies on ultrathin InAs/ InP QWs having zinc-blende structure. 7 These experimental results and theoretical calculations using an envelopefunction scheme with effective-mass approximation and empirical tight-binding model 8 seem to show type-I direct transitions in zinc-blende InAs/InP QWs, although some calculations also predict type-II behavior.9 In contrast, the electronic structure and optical properties of wurtzite InP and InAs are almost unknown. 5,10 Due to the differences in crystal structure and strain, the insights gathered from the studies on zinc-blende InAs/InP QWs cannot be applied directly to wurtzite InP/InAs/InP CMNs.We study the InP/InAs/InP CMNs using time-resolved ͑TR͒ and spectrally resolved ͑SR͒ photoluminescence ͑PL͒ and PL excitation ͑PLE͒ measurements. A large Stokes shift between PL and PLE spectra was observed, which along with the absence of strong PLE peak suggests type-II radiative recombination. With increasing excitation power ͑P͒ the PL peaks show a blueshift with a cu...

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“…Samuelson's group [29] has grown InAs cores ( $ 20-45 nm thick) and InP shells ( $20 nm thick) by VLS using gold catalysis. They observed a photoluminescence peak at 0.7-0.8 eV, which was due to the InAs core nanowire, although the signal-to-noise ratio of their emission was atleast an order of magnitude less than that obtained in the present study.…”

Section: Shown Inmentioning

confidence: 99%