Interband magneto-optics of CdSe and optical spectra of CdSe-based quantum dots

Aliev, G. N.; Andreev, A. D.; Datsiev, R.M.; Иванов, С. В.; Sorokin, S. V.; Kapustina, A.B.; Krestnikov, I. L.; Sasin, M. É.; Seĭsyan, R. P.

doi:10.1016/s0022-0248(98)80067-5

Cited by 5 publications

(1 citation statement)

References 6 publications

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“…However, longwavelength shift of the lasing emission away from the exciton resonance region and moderate values of the enhancement in refractive index [42] limit the device application of this effect in quantum wells. At the same time, absorption measurements [43] demonstrated maximum exciton absorption coef®cients of the order of 10 5 cm 21 in the case of stacked SML QDs. This fact agrees with the estimation of the exciton oscillator strength from the optical re¯ectance spectra and correspond to the values of the refractive index enhancement of about 0.2±0.3.…”

Section: Resonant Waveguiding and Lasingmentioning

confidence: 90%

Quantum dots formed by ultrathin insertions in wide-gap matrices

et al. 2000

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We report on experimental and theoretical studies on a new type of quantum-dot (QD) structures obtained using ultrathin, i.e. below the critical thickness for 2D±3D transition, strained narrow gap insertions in wide bandgap matrices. We concentrate on submonolayer (SML) or slightly above 1 ML CdSe insertions in a wide-gap II±VI matrices and give the ®rst results on ultrathin InGaN insertions in a GaN matrix. A discussion on detailed comparison of our original results with the results of other authors is presented. The formation of dense arrays (up to 10 12 cm 22 ) of nanoscale two-dimensional (2D) islands is revealed in processed high-resolution transmission electron microscopy images. In the case of stacked sheets of SML insertions, the islands in the neighboring sheets are formed predominantly in correlated or anticorrelated way for thinner and thicker spacer layers, respectively. Different polarization of photoluminescence (PL) emission recorded in edge geometry for vertically-uncoupled and coupled QDs con®rms the QD nature of excitons. By monitoring of sharp lines due to single QDs using cathodoluminescence the 3D con®nement is manifested. We demonstrate signi®cant squeezing of the QD exciton wavefunction in the lateral direction using magneto-optical experiments. We point to complete suppression of lateral motion of excitons bound to islands in case of wide-gap (ZnMgSSe) matrices, as follows from PL excitation studies. A resonant (0-phonon) lasing is observed in ultrathin CdSe insertions and proves the lifting of the k-selection rule for QD excitons. We show that lack of exciton screening in QDs up to high excitation densities enables strong resonant modulation of the refractive index in stacked ultrathin insertions and allows realization of resonant (excitonic) waveguiding and lasing. This enables the realization of a new type of heterostructure laser operating without external optical con®nement by layers having lower average refractive indices. Ultrahigh QD excitonic gain in dense arrays of stacked QDs allows a new type of surface-emitting laser. q 2000 Elsevier Science S.A. All rights reserved.

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Section: Resonant Waveguiding and Lasingmentioning

confidence: 90%

Quantum dots formed by ultrathin insertions in wide-gap matrices

et al. 2000

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Arrays of Two-Dimensional Islands Formed by Submonolayer Insertions: Growth, Properties, Devices

Krestnikov

Ledentsov

Hoffmann

et al. 2001

phys. stat. sol. (a)

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103

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Ultrathin insertions of a narrow band-gap material in wide band-gap matrices represent a challenging medium in view of aspects of growth phenomena, unique optical properties, and non-trivial approaches for structural characterization. In a very general case ultrathin submonolayer insertions may form arrays of islands due to the principally discrete nature of the growth front. If the islands are large enough, these islands may act as locally formed quantum well (QW) insertions. If, however, the islands' size is comparable to the Bohr radius and the band-gap difference between the insert and the matrix material is large enough, quantum dots (QD) are formed. Realization of the first or the second regime depends on the surface properties of the substrate and the deposit, particularly, on the tensors of the intrinsic surface stress of both materials and on the lattice mismatch. In this work we consider in detail the case of ultrathin CdSe insertions in wide gap ZnMgSSe matrices: that the nominal thickness is chosen below the critical thickness for threedimensional (3D) island formation. We give an overview of the experimental results available for these structures obtained by submonolayer or about-one monolayer CdSe depositions. A comparison with similar phenomena observed in conventional III-V and III-N systems is given and possible growth scenarios are discussed. We also discuss practical device applications of the structures based on ultrathin insertions for non-traditional devices. Examples of resonant waveguiding and lasing in edge geometry, of surface emitting lasers with low finesse cavities, and of broad-miniband high-frequency Esaki-Tsu anti-dot superlattices are given.

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Control of the electronic properties of CdSe submonolayer superlattices via vertical correlation of quantum dots

et al. 1999

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Structural and optical properties of submonolayer CdSe/ZnSe superlattices grown with varying thickness of the ZnSe spacer layer are studied. High-resolution electron microscopy images demonstrate that submonolayer CdSe depositions result in two-dimensional nanoscale CdSe islands which are anticorrelated for spacer layer thicknesses exceeding 3 nm, while predominantly vertically correlated growth occurs for thinner spacers, in agreement with most recent theoretical predictions. Vertical ordering of the CdSe islands leads to two lines in photoluminescence ͑PL͒ and optical reflectance spectra originating from excitons localized at vertically coupled and uncoupled CdSe quantum islands, respectively. In edge PL, these lines exhibit different polarizations: predominantly TM and predominantly TE for coupled and uncoupled states, respectively. Stimulated emission in edge geometry and resonant waveguiding effects are observed for both states. The TE and TM components of the stimulated emission of the same state show an energy splitting. At the highest excitation densities we observe saturation of the stimulated emission in the edge geometry, and the development of a peak in surface emission that is strongly increasing with excitation intensity. This peak is attributed to stimulated emission in surface geometry, which is made possible by the ultrahigh material gain in quantum dots and the self-adjustment of the gain spectrum and the cavity mode. ͓S0163-1829͑99͒02024-X͔

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Interband magneto-optics of CdSe and optical spectra of CdSe-based quantum dots

Cited by 5 publications

References 6 publications

Quantum dots formed by ultrathin insertions in wide-gap matrices

Quantum dots formed by ultrathin insertions in wide-gap matrices

Arrays of Two-Dimensional Islands Formed by Submonolayer Insertions: Growth, Properties, Devices

Control of the electronic properties of CdSe submonolayer superlattices via vertical correlation of quantum dots

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