Optically detected far-infrared resonances in doped GaAs quantum wells

Kono, Junichiro; Lee, S. T.; Salib, M. S.; Herold, G.; Petrou, A.; McCombe, B. D.

doi:10.1103/physrevb.52.r8654

Cited by 44 publications

(34 citation statements)

References 16 publications

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“…This PL quenching is consistent with the interpretation that the FIR radiation heats photoinjected electrons and holes, which in turn heat and decrease peak emission from luminescing excitons [6]. Numerous experiments have optically detected cyclotron resonance [7][8][9][10][11][12][13], and impurity transitions [14,15] in various bulk semiconductors and quantum heterostructures. The equivalence of ODR and conventional transmission techniques in determining the frequency of absorption resonances has been shown clearly (for example, see [10,11]).…”

supporting

confidence: 62%

“…2p 1 -like resonance. Finally, predictions from donor theory [18] and previous experimental measurements on donors [15,21] do not agree with our data, as can be seen in Fig. 3.…”

contrasting

confidence: 54%

“…The binding energies and FIR transition energies for donors at different positions in GaAs QWs in the presence of magnetic fields have been calculated in detail by Greene and Lane [18]. This theory has been extensively verified by experiments [15,21]. The calculated 1s !…”

mentioning

confidence: 96%

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Terahertz Dynamics of Excitons in GaAs/AlGaAs Quantum Wells

et al. 1996

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By monitoring changes in excitonic photoluminescence that are induced by far-infrared (FIR) radiation, we observed resonant FIR absorption by magnetoexcitons in GaAs͞AlGaAs quantum wells. The dominant resonance is assigned to the 1s ! 2p 1 transition of the heavy-hole exciton, and agrees well with theory. At low FIR and interband excitation intensities, the 1s ! 2p 1 absorption feature is very narrow and broadens as either of these intensities is increased. The 1s ! 2p 1 absorption feature persists even when the FIR electric field is comparable to the electric field which binds the exciton. [S0031-9007 (96) Correlated electron-hole pairs form excitons in semiconductor heterostructures. Excitons in GaAs are hydrogenlike systems with Bohr radii of order 100 Å, and binding energies of order 10 meV. The importance and much of the rich structure of excitons have been revealed by extensive studies using one-and two-photon interband spectroscopies (0.75-1.5 eV in GaAs) [1]. However, very limited research has succeeded in directly exploring the internal dynamics of excitons [2][3][4]. In such studies, near-infrared (NIR) photons create excitons, and then far-infrared (FIR) radiation (of order 10 meV, 2.4 THz) manipulates them. At low FIR intensities, one expects to observe directly transitions between even-and odd-parity states of the exciton, which are not observable with linear interband spectroscopy. Such transitions provide new, sensitive tests for the theory of excitons, which is fundamental in the physics of semiconductors. At higher FIR intensities, it is possible to reach a nonperturbative regime in which the energy associated with the FIR electric field coupling to the exciton is comparable to both the binding energy and the FIR photon energy.Undoped direct (type I) quantum wells (QWs) are especially interesting since they are so commonly used and provide a simple model system for theoretical analysis. However, the short lifetime of excitons in type I QWs makes it difficult to achieve the large population of cold excitons required for FIR absorption studies. Recent experimental progress has been made in QWs using photoinduced absorption in staggered (type II) QWs [3] and time-resolved terahertz spectroscopy in type I QWs [4].

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supporting

confidence: 62%

“…2p 1 -like resonance. Finally, predictions from donor theory [18] and previous experimental measurements on donors [15,21] do not agree with our data, as can be seen in Fig. 3.…”

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confidence: 54%

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Terahertz Dynamics of Excitons in GaAs/AlGaAs Quantum Wells

et al. 1996

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“…In both cases, magnetic fields were present. The D Ϫ donor in GaAs QW's has also been studied very recently by optically detected far-infrared resonance experiments 27 and theoretically 28 by including the electronphonon interaction. However, only hydrogenlike states appear to have been considered in these analyses.…”

Section: Discussionmentioning

confidence: 99%

Landau-like states in the magneto-optical spectrum of a shallow donor impurity: Theory versus experiment

et al. 1996

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A calculation of the energy levels and the wave functions for a shallow donor impurity in an applied magnetic field is put forward. The behavior of the donor electron in directions perpendicular to the field is described by a basis set of Landau wave functions, and a variational procedure is used to generate approximate forms for the wave function along the field axis. Theoretical values for the ionization energies of the impurity are calculated and a comparison with both existing and new experimental data, also reported here, is made for impurities in bulk GaAs. The model is used to obtain hydrogenlike states of the impurity as well as the so-called ''metastable'' or ''autoionizing'' Landau-like states. A comparison with a ''hydrogenic'' method of calculation is used to highlight the validity of the model. Also, transition probabilities from the ground to excited donor states are deduced. The results obtained are used to identify the various peaks observed in experimental spectra. Differences between theory and experiment are attributed to the occurrence of Fano resonances. A discussion of the behavior of the impurity in an applied magnetic field calls into question the expected ordering of the energy levels of such a system. ͓S0163-1829͑96͒05735-9͔

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“…Theoretical predictions of the effect of lateral confinement on internal transitions of X and X − are available [13], and experimental work on internal transitions has been carried out via optically detected resonance (ODR) spectroscopy in quasi-2D systems. ODR spectroscopy is a sensitive technique in which sample PL is excited (typically) by a visible laser, and the small modulation of this characteristic PL induced by resonant absorption of a far infrared (terahertz) laser beam is monitored as a function of some external parameter, usually magnetic field [9,10,14]. This allows sensitive probing of electronic structure in the THz region (resonance is usually achieved by tuning the electronic states via an external magnetic field).…”

Section: Introduction/backgroundmentioning

confidence: 99%

Internal Transitions of Charged Excitons in AlGaAs/GaAs Lateral Fluctuation Quantum Dots

et al. 2004

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Low temperature measurements of magneto-photoluminescence and optically detected resonance spectroscopy in magnetic fields up to 10 T were carried out on GaAs/Al 0.3 Ga 0.7 As quantum well samples grown by molecular beam epitaxy with lateral fluctuation quantum dots produced by growth interruption. Monolayer fluctuations of the quantum well width form lateral quantum dots for which confinement energies are less than Coulomb correlation energies. Five different width quantum wells (2.8-14.1 nm) were grown in a single sample, doped in the barriers with Si donors to allow for photoluminescence of both excitons and trions. We report studies of the optically detected resonance spectra associated with the ensemble photoluminescence of all of the wells including observation of bound-to-continuum internal transitions of trions, both singlet and triplet, and electron cyclotron resonance for the wider wells, which also show a clear bound-to-bound triplet transition. The latter is forbidden by magnetic translational invariance, but can be seen in these samples because this symmetry is broken by the lateral fluctuations, whose characteristic dimensions are greater than the trion orbit size. The two narrowest wells show strong broad optically detected resonance signals associated with inhomogeneously broadened internal transitions of the strongly correlated trions in the lateral dots. The optically detected resonance signals peak well below the calculated positions of electron cyclotron resonance. As expected for localized carriers and excitons, there is no free electron cyclotron resonance. We also present preliminary measurements of optically detected resonance spectra from a single dot.

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Optically detected far-infrared resonances in doped GaAs quantum wells

Cited by 44 publications

References 16 publications

Terahertz Dynamics of Excitons in GaAs/AlGaAs Quantum Wells

Terahertz Dynamics of Excitons in GaAs/AlGaAs Quantum Wells

Landau-like states in the magneto-optical spectrum of a shallow donor impurity: Theory versus experiment

Internal Transitions of Charged Excitons in AlGaAs/GaAs Lateral Fluctuation Quantum Dots

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