TEM observation of threading dislocations in InAs self-assembled quantum dot structure

Shiramine, K.; Horisaki, Yasunobu; Suzuki, Dai; Itoh, Satoru; Ebiko, Yoshiki; Muto, Shunichi; Nakata, Yoshihiro; Yokoyama, Naoki

doi:10.1016/s0022-0248(99)00309-7

Cited by 14 publications

(12 citation statements)

References 13 publications

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“…Shiramine et al observed similar extensive threading dislocations. 22,23 However these threading dislocations are created during growth and unlike our defects are clearly aligned at 55°to the ͑001͒ plane and therefore glide on the ͕111͖ planes. They propose that the dislocations form as a result of strain in the vicinity of two islands that nucleate close together during growth.…”

Section: Cross-sectional Transmission Electron Microscopymentioning

confidence: 81%

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

Stewart

Buda

Wong‐Leung

et al. 2003

Journal of Applied Physics

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Effect of GaP strain compensation layers on rapid thermally annealed In Ga As ∕ Ga As quantum dot infrared photodetectors grown by metal-organic chemical-vapor deposition Appl. Phys. Lett. 91, 073515 (2007); 10.1063/1.2770765Effects of rapid thermal annealing on device characteristics of In Ga As ∕ Ga As quantum dot infrared photodetectors Normal incidence InAs/Al x Ga 1−x As quantum dot infrared photodetectors with undoped active region In this article the effect of rapid thermal annealing ͑RTA͒ on a 30 stacked InAs/GaAs, molecular beam epitaxially grown quantum dot infrared photodetector ͑QDIP͒ device is studied. Temperatures in the range of 600-800°C for 60 s, typical of atomic interdiffusion methods are used. After rapid thermal annealing the devices exhibited large dark currents and no photoresponse could be measured. Double crystal x-ray diffraction and cross sectional transmission electron microscopy studies indicate that this could be the result of strain relaxation. V-shaped dislocations which extended across many quantum dot ͑QD͒ layers formed in the RTA samples. Smaller defect centers were observed throughout the as-grown sample and are also likely a strain relaxation mechanism. This supports the idea that strained structures containing dislocations are more likely to relax via the formation of dislocations and/or the propagation of existing dislocations, instead of creating atomic interdiffusion during RTA. Photoluminescence ͑PL͒ studies also found that Si related complexes developed in the Si doped GaAs contact layers with RTA. The PL from these Si related complexes overlaps and dominates the PL from our QD ground state.

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Section: Cross-sectional Transmission Electron Microscopymentioning

confidence: 81%

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

Stewart

Buda

Wong‐Leung

et al. 2003

Journal of Applied Physics

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“…[5][6][7][8] While there have been quite a few studies of defects formed in freestanding, uncapped QDs grown in the Stranski-Krastanow growth mode, 1,2,9,10 there seems to be relatively few studies of the defects generated during capping of the QDs. [11][12][13] However, for most device applications, these islands must be capped with a material of wider band gap ͑e.g., a GaAs cap in the case of InAs/ GaAs QDs͒ in order to achieve the beneficial 3D confinement effects. During an extensive study of the various growth parameters 14 on InAs/ GaAs QD nucleation, three main defect types were observed under certain growth conditions.…”

Section: Introductionmentioning

confidence: 99%

A transmission electron microscopy study of defects formed through the capping layer of self-assembled InAs∕GaAs quantum dot samples

Sears

Wong‐Leung

Tan

et al. 2006

Journal of Applied Physics

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Analytical approach for strain and piezoelectric potential in conical self-assembled quantum dots J. Appl. Phys. 104, 083524 (2008); 10.1063/1.2999639 N incorporation into InGaAs cap layer in InAs self-assembled quantum dots Effects of seed layer on the realization of larger self-assembled coherent InAs/GaAs quantum dots Plan-view and cross-sectional transmission electron microscopy have been used for a detailed study of the defects formed in capped InAs/ GaAs quantum dot ͑QD͒ samples. Three main types of defects, V-shaped defects, single stacking faults, and stacking fault pyramids, were found to form under growth conditions that led to either very large, indium enriched, or coalesced islands. All three types of defects originate at the buried quantum dot layer and then travel through the GaAs cap to the surface on the ͕111͖ planes. The V-shaped defects were the most common and typically consisted of two pairs of closely spaced 60°Shockley partials with a ͗211͘ line direction. The two pairs originate together at the buried QD layer and then travel in "opposite" directions on different ͕111͖ planes. The second type of defect is the single stacking fault which consists of a single pair of partial dislocations separated by an Ϸ50 nm wide stacking fault. Finally, both complete and incomplete stacking fault pyramids were observed. In the case of the complete stacking fault pyramid the bounding dislocations along the ͓110͔, ͓110͔, ͓101͔, and ͓101͔ directions were identified as stair rods. A possible mechanism for the stacking fault pyramid formation, which can also account for the creation of incomplete stacking fault pyramids, is presented.

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“…The details of the in-plane HRXRD characterization technique are described in our previous publication. 14 The in-plane high-resolution X-ray RSM at the (004) reflection was performed to study the strain field around the InAs QDs and to analyze the existence of the selfassembled In x Ga 1−x As layer as well as its corresponding broadening width (β). 2θχ/ϕ RSM at the (004) reflection was conducted by detecting each diffracted 2θχ lattice point map for every small-step change in ϕ at the (004) plane by using a monochromatic setup with a scanning point detector.…”

Section: Methodsmentioning

confidence: 99%

“…13 Shiramine et al reported two general mechanisms underlying threading dislocations during the growth of GaAs capping layers by MBE: (i) dislocation initiating from the region of the overlap between two large islands and (ii) dislocation caused by a misfit between the relaxed InAs islands and the GaAs layer, which results in the threading of the epilayer in the {111} plane. 14 In addition, interface roughness due to deposition of the capping layer is another major reason for leakage of the indium adatoms from the surface of the InAs islands. To achieve an emission wavelength of 1.3 μm with narrow spectra for the application of single-photon sources at the O-band telecom wavelength, uniform deposition of a capping layer and consistent material composition are desired.…”

Section: Introductionmentioning

confidence: 99%

Impact of an In_xGa_1–xAs Capping Layer in Impeding Indium Desorption from Vertically Coupled InAs/GaAs Quantum Dot Interfaces

Tongbram

Sengupta

Chakrabarti

2018

ACS Appl. Nano Mater.

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This study describes the effect of a thin GaAs spacer of 4.5 nm thickness in a bilayer-coupled InAs quantum dot (QD) heterostructure. Here, we report the first demonstration of InAs/GaAs QDs capped by self-assembled In x Ga1–x As layers. Self-assembled In x Ga1–x As layers were introduced into each intermediate layer across the interface of InAs QDs and the GaAs layer in a vertical-coupled bilayer QD (VCBQD) heterostructure to prevent indium desorption from the QDs. A change in the indium content in the seed-layer InAs QDs changes the self-assembly position and modifies the In x Ga1–x As layer thickness. A theoretical approach was presented to study the formation of self-assembled In x Ga1–x As layers at each strain-free layer. We showed that the strain energy at the second intermediate (ε zz2) layer is greater than that at the first intermediate (ε zz1) layer; ε zz2 depends on the vertical strain channel length. The impact of the In x Ga1–x As layer thickness on the strain energy was studied using high-resolution transmission electron microscopy; a shorter strain channel length was found to facilitate the formation of a more relaxed and larger-sized self-assembled In x Ga1–x As layer in the active layer. This In x Ga1–x As layer formed at the intermediate layer acts as a capping layer or a protective shield for the indium adatoms, preventing their desorption from the InAs QDs. Furthermore, we studied the thermal stability of the self-assembled In x Ga1–x As layer by annealing the VCBQD samples at 700 and 800 °C. This aspect has been investigated for the first time ever in a study of the coupling efficiency between the InAs QDs and In x Ga1–x As capping layer. A high-resolution in-plane (2θχ/ϕ) reciprocal space mapping (RSM) technique provided the connection between the in-plane reciprocal lattice point of the InAs QDs and In x Ga1–x As layers and revealed the strain and coupling between them. InAs QDs fully covered with the self-assembled In x Ga1–x As layer enhanced the photoluminescence intensity by 77% and had an activation energy of 467 meV.

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TEM observation of threading dislocations in InAs self-assembled quantum dot structure

Cited by 14 publications

References 13 publications

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

A transmission electron microscopy study of defects formed through the capping layer of self-assembled InAs∕GaAs quantum dot samples

Impact of an In_xGa_1–xAs Capping Layer in Impeding Indium Desorption from Vertically Coupled InAs/GaAs Quantum Dot Interfaces

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TEM observation of threading dislocations in InAs self-assembled quantum dot structure

Cited by 14 publications

References 13 publications

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

A transmission electron microscopy study of defects formed through the capping layer of self-assembled InAs∕GaAs quantum dot samples

Impact of an InxGa1–xAs Capping Layer in Impeding Indium Desorption from Vertically Coupled InAs/GaAs Quantum Dot Interfaces

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Impact of an In_xGa_1–xAs Capping Layer in Impeding Indium Desorption from Vertically Coupled InAs/GaAs Quantum Dot Interfaces