Evidence for strain in and around InAs quantum dots in GaAs from ion-channeling experiments

Selen, Lena; IJzendoorn, L.J. van; Voigt, M.J.A. de; Koenraad, P. M.

doi:10.1103/physrevb.61.8270

Cited by 23 publications

(11 citation statements)

References 14 publications

(14 reference statements)

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“…been shown that strain fields due to lattice mismatch S 1.30 -extend from the QDs into surrounding GaAs matrix _ E E over > 10 nm [23]. Such a strain field increases vacancy a 1.25 concentration [23] and is likely to enhance the lateral 0.…”

Section: Sr2mentioning

confidence: 99%

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Post-growth thermal treatment of self-assembled InAs/GaAs quantum dots

Babiński

Jasiński

2002

Thin Solid Films

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Section: Sr2mentioning

confidence: 99%

“…Such a strain field increases vacancy a 1.25 concentration [23] and is likely to enhance the lateral 0.…”

Section: Sr2mentioning

confidence: 99%

Post-growth thermal treatment of self-assembled InAs/GaAs quantum dots

Babiński

Jasiński

2002

Thin Solid Films

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“…It has also been shown that strain field can extend from the QDs into surrounding GaAs matrix over a typical scale of ജ10 nm. [32][33][34] The extended strain field might cause migrations of native defects, such as vacancies and interstitials, to the vicinity of the quantum dots. During our sample growth, because of the relatively thick upper GaAs confining layers, the dots were subjected to an anneal of about 20 min at 580°C, which could enhance the migration of the defects.…”

mentioning

confidence: 99%

Coexistence of deep levels with optically active InAs quantum dots

et al. 2005

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We present direct experimental evidence of the coexistence of deep levels with intrinsic quantum confinement states in large, self-assembled InAs quantum dots embedded in a GaAs matrix. The InAs quantum dots show very good optical properties, as evidenced by the strong photoluminescence at room temperature at ϳ1.3 m. Deep levels 160 and 484 meV below the GaAs conduction band edge have been identified at large reverse biases and high temperatures using deep level transient spectroscopy ͑DLTS͒ measurements. The reverse-bias dependence of the DLTS signal together with experimental results from the reference samples, containing thin InAs layers but no quantum dots, confirms that the deep levels coexist in the same layer as the InAs dots, and are most likely caused by the strain field during the lattice mismatched growth process. The densities of the deep levels in the structure are comparable to the density of the optically active quantum dots.Considerable efforts have been expended in the study of self-assembled semiconductor quantum dots ͑QDs͒, grown by the Stranski-Krastanov growth mode, because of their importance in device applications and in fundamental physics. 1,2 The excellent optical properties, such as strong photoluminescence ͑PL͒ intensity, are generally attributed to the coherent nature, i.e., defect free, of the QD islands. 1-6 In recent years, however, an increasing number of experiments have suggested the possibility that electronic deep levels might exist around or in what were regarded as coherent QDs that exhibit strong PL signals. For example, the presence of defects was suggested as a possible reason for the absence of the so-called phonon-bottleneck effect. 7,8 Other optical experiments, such as the quenching of PL signals at high temperatures, also suggested the possible existence of deep level defects around the QDs. 9-11 Dai et al. pointed out that the defect related centers existed at the InAs/ GaAs interface and played an important role in the PL quenching process. 12 They also indicated that the energy of the interface defects depended on the size of the quantum dots. By performing timeresolved optical characterizations of InAs QDs in GaAs, Fiore et al. speculated on the existence of nonradiative traps in the ͑In͒GaAs matrix in the close vicinity of the QDs, which would capture the carriers before they relaxed into the QDs. 13 Despite the evidence of the existence of unknown deep levels, the optical experiments could not provide confirmation and direct information, such as energy levels and concentrations, of possible deep levels due to their generally nonradiative nature. The electrical space-charge technique, deep level transient spectroscopy ͑DLTS͒, 14 has recently been used to characterize QD structures, but most efforts have been focused on the intrinsic QD states. 15-21 The electrons can be thermally emitted out from the dots and then be detected by DLTS only when their electronic states are lifted above the bulk Fermi level. Therefore, by careful adjustment of the filling/reverse b...

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“…The strain in and around buried quantum dots is relieved via extended strain fields, which also results in inhomogeneous deformations in the host lattice. It is known from strain measurements and calculations on buried quantum dots that those strain fields extend up to tenths of nm into the host crystal, 13,14 which can be compared to the values for the distortion length we found above.…”

Section: IIImentioning

confidence: 99%

“…After implantation a 10 s rapid thermal anneal ͑RTA͒ in dry nitrogen was applied at a temperature of 1050°C. Two samples were prepared by implanting doses of 3ϫ10 14 and 3ϫ10 15 B/cm 2 .…”

Section: Methodsmentioning

confidence: 99%

Channeling on boron clusters in silicon

Selen

IJzendoorn

Loon

et al. 2001

Journal of Applied Physics

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Low energy ion implantation at high doses of boron (Ͼ10 15 cm Ϫ2 ) in Si is necessary for the fabrication of ultrashallow junctions but can result in the undesirable presence of boron clusters. Values for the dimensions of the lattice distortions in the implanted Si are obtained by comparing the enhanced dechanneling and the direct scattering peak in the region with clusters in a channeled Rutherford backscattering spectrometry spectrum to those from Monte Carlo calculations on a curved crystal structure. Values of about 0.17 and 65 nm are found for the maximum deformation and the length of the distortions in the crystal, respectively, which implies that the lattice distortions extend significantly outside the layer in which the B clusters are supposed to be present.

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Evidence for strain in and around InAs quantum dots in GaAs from ion-channeling experiments

Cited by 23 publications

References 14 publications

Post-growth thermal treatment of self-assembled InAs/GaAs quantum dots

Post-growth thermal treatment of self-assembled InAs/GaAs quantum dots

Coexistence of deep levels with optically active InAs quantum dots

Channeling on boron clusters in silicon

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