Determination of the strain generated in InAs/InP quantum wires: prediction of nucleation sites

Molina, S. I.; Ben, T.; Sales, DL; Pizarro, J.; Galindo, Pedro L.; Varela, M.; Pennycook, S. J.; Fuster, David; González, Y.; González, L.

doi:10.1088/0957-4484/17/22/020

Cited by 32 publications

(23 citation statements)

References 18 publications

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“…The location of the minimum chemical potential at the growth surface (preferential nucleation sites) corresponds approximately to the positions of minimum strain energy calculated by FEA. Since experimental and simulated values are in good agreement, one can conclude that this estimate allows the successful prediction of the stacking angles of the studied nanowires [67,68].…”

Section: Simulated and Experimental Determination Of Strain Map And Psupporting

confidence: 60%

High-Resolution Electron Microscopy of Semiconductor Heterostructures and Nanostructures

Sales

Beltrán

Lozano

et al. 2012

Semiconductor Research

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This chapter briefly describes the fundamentals of high-resolution electron microscopy techniques. In particular, the Peak Pairs approach for strain mapping with atomic column resolution, and a quantitative procedure to extract atomic column compositional information from Z-contrast high-resolution images are presented. It also reviews the structural, compositional, and strain results obtained by conventional and advanced transmission electron microscopy methods on a number of III-V semiconductor nanostructures and heterostructures.

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Section: Simulated and Experimental Determination Of Strain Map And Psupporting

confidence: 60%

High-Resolution Electron Microscopy of Semiconductor Heterostructures and Nanostructures

Sales

Beltrán

Lozano

et al. 2012

Semiconductor Research

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“…[28][29][30] The studied material in our case is formed by a disordered substitutional InAs x P 1−x alloy with a chemical composition that changes from atomic column to atomic column throughout the studied nanowires. 31 InAs-rich regions appear brighter in the image while a reduction of the intensity occurs as the InP content of the analyzed atomic columns increases. The shape and composition of the imaged nanowire are clearly identifiable in the image of Fig.…”

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confidence: 96%

Direct imaging of quantum wires nucleated at diatomic steps

Molina

Varela

Sales

et al. 2007

Applied Physics Letters

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Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. In the presence of misfit strain, we show that the nucleation process takes place preferentially at the upper terrace of the step as a result of the local stress relaxation. Evidence for strain-induced nucleation comes from the direct observation by postgrowth, atomic resolution, Z-contrast imaging of an InAs-rich region in a nanowire located on the upper terrace surface of an interfacial diatomic step. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2790483͔Atomic steps located at the surfaces of substrates play a central role in controlling the growth mechanism of a wide range of materials. The effect of such steps on the growth process, the morphology, the stress and strain distributions, and the functionality of the materials has been extensively investigated. [1][2][3][4][5][6][7][8][9][10][11] In particular, these steps are thought to constitute a heterogeneous source of nucleation for the formation of nano-objects and structural defects at the initial stages of the growth of many semiconductor nanostructures. 12,13 It is critically important to identify the nucleation sources for individual nano-objects such as quantum dots and wires because they constitute the fundamental blocks of future nanoelectronics and nanophotonics devices. 14 The ability to control the nucleation of these nano-objects will contribute significantly to the development of reliable single-photon sources for applications in quantum information technology. [15][16][17] Nanowires constitute a special case of self-assembled nano-objects. 18 Self-assembled nano-objects can be formed spontaneously via the Stranski-Krastanov growth mode for certain semiconductor materials when a few monolayers are epitaxially deposited on a lattice-mismatched substrate. 19,20 Strain is widely accepted to be the driving force for the nucleation of these nano-objects, but as yet there has been no direct experimental evidence for the role of steps, and their associated stress enhancement, in the self-organized growth of nanowire arrays. 21,22 In this letter we show the direct imaging, by aberrationcorrected Z-contrast scanning transmission electron microscopy ͑STEM͒ and atomic force microscopy, that, in the presence of misfit strain, nanowires preferentially nucleate on the upper terrace of a diatomic step. With finite element elasticity calculations, we demonstrate that the driving force is the stress relaxation at the upper terrace of a diatomic step, which explains the observed nucleation site of semiconductor nanowires.The nanowires investigated consist of InAs͑P͒ selfassembled quantum wires grown by solid source molecular beam epitaxy ͑MBE͒ on InP ͑001͒ substrates. The lattice mismatch between InAs and InP is 3.2%. The control of the relaxation process of these nanostructures has recently been followed with high precision by in situ accumulated stress measurements from the initial phases of the self-assembly process. 23 The process of format...

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“…10 In this context, although the QWR formation in the lower layers and its shape can be associated with the substrate misorientation, the subsequent formation and the arrangement in tilted columns is more likely associated with the strain fields created by the buried nanostructures. 11 We have analysed the optical properties of these samples by means of PL and time-resolved photoluminescence (TRPL). As excitation source, we use either a continuous wave (CW) laser (Ti:Sapphire crystal pumped by a neodymium yttrium vanadate (Nd:YVO4) laser, Spectra Physics) or a pulsed laser diode (PicoQuant), in both cases emitting at 780 nm.…”

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confidence: 99%

InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

Alonso-Álvarez

Thomas

Führer

et al. 2014

Applied Physics Letters

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Quantum wires (QWRs) form naturally when growing strain balanced InGaAs/GaAsP multi-quantum wells (MQW) on GaAs [100] 6° misoriented substrates under the usual growth conditions. The presence of wires instead of wells could have several unexpected consequences for the performance of the MQW solar cells, both positive and negative, that need to be assessed to achieve high conversion efficiencies. In this letter, we study QWR properties from the point of view of their performance as solar cells by means of transmission electron microscopy, time resolved photoluminescence and external quantum efficiency (EQE) using polarised light. We find that these QWRs have longer lifetimes than nominally identical QWs grown on exact [100] GaAs substrates, of up to 1 μs, at any level of illumination. We attribute this effect to an asymmetric carrier escape from the nanostructures leading to a strong 1D-photo-charging, keeping electrons confined along the wire and holes in the barriers. In principle, these extended lifetimes could be exploited to enhance carrier collection and reduce dark current losses. Light absorption by these QWRs is 1.6 times weaker than QWs, as revealed by EQE measurements, which emphasises the need for more layers of nanostructures or the use light trapping techniques. Contrary to what we expected, QWR show very low absorption anisotropy, only 3.5%, which was the main drawback a priori of this nanostructure. We attribute this to a reduced lateral confinement inside the wires. These results encourage further study and optimization of QWRs for high efficiency solar cells.

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Determination of the strain generated in InAs/InP quantum wires: prediction of nucleation sites

Cited by 32 publications

References 18 publications

High-Resolution Electron Microscopy of Semiconductor Heterostructures and Nanostructures

High-Resolution Electron Microscopy of Semiconductor Heterostructures and Nanostructures

Direct imaging of quantum wires nucleated at diatomic steps

InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

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