One-dimensional continuum and exciton states in quantum wires

Akiyama, Hidefumi; Yoshita, Masahiro; Pfeiffer, L. N.; West, K. W.; Pinczuk, A.

doi:10.1063/1.1539552

Cited by 37 publications

(31 citation statements)

References 31 publications

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“…Trions have been observed very recently in modulation-doped QWRs [24] over a wide range of electron densities. In particular, an enhanced trion binding energy with respect to the QW situation was found.…”

Section: Trions In Quantum Wiresmentioning

confidence: 99%

Theory of Trion Spectra in Semiconductor Nanostructures

Esser

Zimmermann

Runge

2001

phys. stat. sol. (b)

102

110

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A consistent density-matrix approach for the absorption spectra of semiconductor nanostructures at finite carrier densities is presented that describes both bound and scattering three-particle states (trions). It automatically includes the two-particle bound states (excitons). In optical transitions, the initial electron or hole momentum is transferred to the final trion state, which --due to recoil energy --gives rise to low-energy tails at the trion and exciton line. A high-energy tail at the exciton is due to the exciton-electron scattering states (trion continuum). The incomplete transfer of exciton oscillator strength to the main trion line and the trion continuum is exemplified by a quantum wire calculation.

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Section: Trions In Quantum Wiresmentioning

confidence: 99%

Theory of Trion Spectra in Semiconductor Nanostructures

Esser

Zimmermann

Runge

2001

phys. stat. sol. (b)

102

110

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“…The sharp PL peak of free excitons dominates the spectrum at the lower pump powers. The free exciton peak has narrow width of 1.5 meV and displays a small Stokes shift of 0.5 meV from the position of the free exciton absorption measured in PLE spectra, and is highly uniform over the whole wire length of 500 µm [18]. Much weaker PL peaks in the low energy region vary in intensity at different positions in the sample, and are ascribed to localized excitons.…”

mentioning

confidence: 93%

“…The high uniformity of the sample was characterized by micro-PL and PL-excitation (PLE) measurements under weak point excitation, which is reported elsewhere [18] together with details of fabrication procedures.…”

mentioning

confidence: 99%

Coulomb-correlated electron-hole plasma and gain in a quantum-wire laser of high uniformity

Akiyama

Pfeiffer²,

Yoshita

et al. 2003

Phys. Rev. B

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A multi-quantum wire laser operating in the 1-D ground state has been achieved in a very high uniformity structure that shows free exciton emission with unprecedented narrow width and low lasing threshold. Under optical pumping the spontaneous emission evolves from a sharp free exciton peak to a red-shifted broad band. The lasing photon energy occurs about 5 meV below the free exciton. The observed shift excludes free excitons in lasing and our results show that Coulomb interactions in the 1-D electron-hole system shift the spontaneous emission and play significant roles in laser gain.PACS numbers: 78.67. Lt, 78.45.+h, 78.55.Cr, 73.21.Hb Quantum wire lasers provoke fundamental questions stemming from the singular nature of one-dimensional (1-D) densities of state [1,2,3,4,5,6,7]. A quantum wire laser was first achieved by Kapon and coworkers in 1989 [2], though lasing occurred only at higher subbands in multi-mode wires. In 1993, Wegscheider and coworkers [3] demonstrated ground-state lasing in quantum wires. They found that the lasing energy was exactly at the peak of excitonic spontaneous emission, and was nearly independent of pump levels. This suggested absence of band-gap renormalization and an enhanced stability of 1-D excitons. Therefore, the origin of gain was ascribed to excitons.As for the enhanced stability and activity of 1-D excitons in narrow quantum wires, there have been numbers of theories [4,5,6,7] and experiments [8], for example, on binding energy [9], oscillator strength [10], and many-body effects [11,12,13,14]. In particular, lack of red-shift in photoluminescence (PL) under high photoexcitation levels has been reported in various 1-D systems [3,11,12,13,14].General arguments suggest that free excitons cannot cause lasing [15] since the electron-hole population will not become inverted until a density approaching one exciton per Bohr radius. At such a density the excitonic correlations will be transient and such a system is probably better described as a Coulomb-correlated electron-hole plasma. The argument can be subverted if the excitons become localized [13] in low energy states produced by disorder or impurities, and therefore it is important to study systems of extremely high uniformity.In this letter, we report stimulated and spontaneous emissions of a quantum wire laser with greatly improved uniformity. Remarkably, optically pumped lasing is ob- served with a lower threshold than in previous quantum wire lasers [3,11]. Free exciton emission is extraordinarily sharp for quantum wires, while localized exciton emission is very weak and does not seem to play an important role in the gain of this laser. Lower lasing threshold and enhanced free exciton properties are attributed

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“…A similarly polarized peak on the lower energy side of MQW1 has been also observed in the CdTe/CdMgTe system [5]. We were somewhat surprised by the small FWHM of this line; but here we note that others working on similar CEO-grown quantum wires based on GaAs/GaAlAs also observe surprisingly narrow lines in similar structures [3].…”

Section: Qw2mentioning

confidence: 76%

ZnCdSe quantum structures by (110)‐cleaved‐edge overgrowth: MBE growth and μ‐PL characterization

Titova

Cywiński

Kutrowski

et al. 2004

Physica Status Solidi (b)

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PACS 78.55.Et, 78.67.Lt Cleaved edge overgrowth has been used to fabricate zero-and one-dimensional ZnCdSe nanostructures in a ZnSe matrix. Polarization-dependent micro-photoluminescence results indicate that 0-D structures (quantum dots) are present in the entire overgrowth region due to (110) interface roughness, while 1-D structures (quantum wires) appear only in the region where quantum wells grown on (001) and (110) 1 Introduction Low dimensional semiconductor quantum structures continue to be the subject of intense fundamental as well as applied research activity. We have recently begun a study focused on II-VIbased quantum structures formed by the method of cleaved-edge overgrowth (CEO). CEO offers the possibility of depositing epitaxial layers on a surface that has not been contaminated by exposure to the atmosphere, thus opening a new situation for growth dynamics; and -as has already been demonstrated in the case of GaAs/AlGaAs [1-4], CdTe/CdMgTe [5] and CdTe/CdZnTe [6,7] heterostructures -the CEO of multiple quantum wells can also be used to form structures of dimensionality lower than 2.Here we discuss CEO of ZnCdSe/ZnSe on GaAs, which is a closely lattice matched combination, in contrast with CdTe-based structures grown on GaAs [5]. This is advantageous since it precludes excessive formation of dislocations. In addition to preliminary success in fabricating ZnCdSe quantum wires in the ZnSe matrix, this work has also resulted in the formation of zero-dimensional (0-D) ZnSe/ZnCdSe quantum structures (so called "natural" quantum dots [8][9][10]) with exceptionally strong exciton localization.

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One-dimensional continuum and exciton states in quantum wires

Cited by 37 publications

References 31 publications

Theory of Trion Spectra in Semiconductor Nanostructures

Theory of Trion Spectra in Semiconductor Nanostructures

Coulomb-correlated electron-hole plasma and gain in a quantum-wire laser of high uniformity

ZnCdSe quantum structures by (110)‐cleaved‐edge overgrowth: MBE growth and μ‐PL characterization

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