Charge separation in coupled InAs quantum dots and strain-induced quantum dots

Schoenfeld, Winston V.; Lundström, T.; Petroff, P. M.; Gershoni, D.

doi:10.1063/1.123798

Cited by 34 publications

(13 citation statements)

References 17 publications

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“…Two innovative methods have been recently used to optically charge QDs. The first utilizes spatial separation of photogenerated electron hole (e-h) pairs in coupled narrow and wide GaAs QWs, separated by a thin AlAs barrier layer [5]. In this case, the lowest energy conduction band in the AlAs barrier (X band) is lower than the conduction band of the narrow QW, but higher than that of the wide one.…”

Section: Samples and Experimental Resultsmentioning

confidence: 99%

“…Sample A, which is used here as a control, neutral sample, consists of a layer of low density In(Ga)As SAQDs embedded only within a thick layer of GaAs [22]. Sample B, which we used for optical charging, consists of a layer of similar SAQDs, embedded within the wider of two coupled GaAs QWs, separated by a thin AlAs barrier layer [5].…”

Section: Samples and Experimental Resultsmentioning

confidence: 99%

“…Semiconductor quantum dots (QDs) are of fundamental and technological contemporary interest mainly for their similarities to the fundamental building blocks of nature, (they are often referred to as "artificial atoms" [1][2][3]) and because they are considered as the basis for new generations of lasers [4], memory devices [5], electronics [6] and quantum computing [7].…”

Section: Introductionmentioning

confidence: 99%

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Optical spectroscopy of single quantum dots at tunable positive, neutral, and negative charge states

et al. 2001

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We report on the observation of photoluminescence from positive, neutral and negative charge states of single semiconductor quantum dots. For this purpose we designed a structure enabling optical injection of a controlled unequal number of negative electrons and positive holes into an isolated InGaAs quantum dot embedded in a GaAs matrix. Thereby, we optically produced the charge states -3, -2, -1, 0, +1 and +2. The injected carriers form confined collective 'artificial atoms and molecules' states in the quantum dot. We resolve spectrally and temporally the photoluminescence from an optically excited quantum dot and use it to identify collective states, which contain charge of one type, coupled to few charges of the other type.These states can be viewed as the artificial analog of charged atoms such as H − , H −2 , H −3 , and charged molecules such as H + 2 and H +2 3 . Unlike higher dimensionality systems, where negative or positive charging always results in reduction of the emission energy due to electron-hole pair recombination, in our dots, negative charging reduces the emission energy, relative to the charge-neutral case, while positive charging increases it. Pseudopotential model calculations reveal that the enhanced spatial localization of the hole-wavefunction, relative to that of the electron in these dots, is the reason for this effect.

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Section: Samples and Experimental Resultsmentioning

confidence: 99%

Section: Samples and Experimental Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical spectroscopy of single quantum dots at tunable positive, neutral, and negative charge states

et al. 2001

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“…However, few works were done in this field. Recently, Schoenfeld et al 1 have designed a QD device that can separate and store photoexcited electrons and holes. Their structure consisted of two GaAs quantum wells of different thickness, separated by a thin AlAs barrier.…”

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confidence: 99%

Photoluminescence of InAs quantum dots inn-i-p-iGaAs superlattice

Wang

Chen

et al. 2000

Phys. Rev. B

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Large blueshift and linewidth increase in photoluminescence ͑PL͒ spectra of InAs quantum dots ͑QD's͒ in n-i-p-i GaAs superlattice were observed. By increasing the excitation intensity from 0.5 to 32 W/cm 2 , the PL peak position blueshifted 18 meV, and the linewidth increased by 20 meV. Such large changes are due to the state-filling effects of the QD's resulted from the separation of photogenerated electrons and holes caused by the doping potential.The optical properties of InAs self-assembled quantum dots ͑QD's͒ have been of great interest in recent years. The interband and intraband optical transitions of these QD's are widely studied, both for the interest in fundamental physical properties and for the development of QD lasers and photodetectors. It is important to investigate electron-hole separation effects in QD's and design QD structures that can separate and store photoexcited carriers for memory-device applications. However, few works were done in this field. Recently, Schoenfeld et al.1 have designed a QD device that can separate and store photoexcited electrons and holes. Their structure consisted of two GaAs quantum wells of different thickness, separated by a thin AlAs barrier. An InAs QD layer is inserted in the thick quantum well. The strain these InAs QD's create induces QD's within the thin GaAs quantum well that are coupled to the InAs QD's in the thick well. In their structure, photogenerated electrons and holes are spatially separated into the InAs QD's and strain-induced QD's, respectively.In this work, we study a different QD structure designed to spatially separate and store photogenerated electrons and holes. In this structure, InAs self-assembled QD's were grown in the n-type and p-type regions of a n-i-p-i GaAs superlattice. Photogenerated electrons and holes in GaAs barriers are expected to be swept by the intrinsic electric field to the n-doped regions and the p-doped regions, respectively, and trapped by the InAs QD's there. As the photogenerated electrons and holes fill up the lower QD states, photoluminescence ͑PL͒ properties of these InAs QD's different from conventional QD's inserted in intrinsic GaAs layers are expected. In our PL experiments, large blueshift of the PL peak and increase of the PL linewidth with increasing excitation intensity were observed for the QD's in the n-i-p-i GaAs superlattice, whereas for similar InAs QD's in intrinsic GaAs layers, only a small blueshift of the PL peak and increase of the linewidth were observed. The large blueshift in the n-ip-i QD's is a clear indication of the state filling of the QD's due to electron-hole separation.The samples were grown by molecular-beam epitaxy on a ͑001͒ N ϩ GaAs substrate. After deposition of a 1-m semiinsulating GaAs type buffer layer, 10 periods of n-type GaAs ͑20 nm͒/InAs QD's (2 ML)/n-type GaAs (20 nm)/p-type GaAs ͑20 nm͒/InAs QD's (2 ML)/p-type GaAs ͑20 nm͒ were grown. The n-type regions were Si doped and the p-type regions were Be doped; both n and p doping concentrations are 1ϫ10 18 cm Ϫ3 . The growth t...

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“…There is emerging interest in memory devices and infrared detectors [1][2][3][4] which use quantum dots (QDs) as charge reservoirs [5][6][7][8][9]. The excitons confined in QDs in these applications are emitted into a twodimensional (2D) conduction layer by external perturbations such as gate voltage or infrared photons.…”

Section: Introductionmentioning

confidence: 99%