Exciton dynamics in Cd0.33Zn0.67Te/ZnTe single quantum wells (original) (raw)
1993, Physica B: Condensed Matter
Sign up for access to the world's latest research
checkGet notified about relevant papers
checkSave papers to use in your research
checkJoin the discussion with peers
checkTrack your impact
Abstract
A series of Cd ,, ,,Zn,, ,,TeiZnTe single quantum wells of thickness 40 A, 70 A and 100 A are studied using CW and time-resolved photoluminescence techniques. The exciton-phonon interaction is found to decrease with decreasing well thickness, this result having implications for room temperature devices. Time-resolved measurements reveal photoluminescence lifetimes increasing with temperature showing that the recombination at low temperatures is predominantly radiative.
Related papers
Temperature effects on exciton and trion states in CdTe quantum well structures
We study the temperature-dependent modifications of trion and exciton photoluminescence (PL) spectra in modulation-doped CdTe/CdMgTe quantum wells in high magnetic field. We find that, in magnetic field, the temperature-dependent redistribution of exciton and trion PL intensities is opposite to that expected from a simple Boltzmann distribution model. Solving a system of rate equations that describe the exciton-trion energy levels, we calculate the temperature dependence of the exciton and trion PL intensities. The calculations show good agreement with the experimental data.
Applied Surface Science, 1991
The technique of resonant Rayleigh scattering is used to determine the homogeneous linewidth across the inhomogeneously broadened exciton resonance in a Cd0.25Zn0.75Te/ZnTe multiple quantum well structure. An order of magnitude increase of the Rayleigh scattering signal over background is observed on tuning a narrow-band laser through the exciton resonance at low temperatures. Spectral and temporal measurements show the effect to be a true scattering process rather than luminescence. The interface and alloy fluctuations in the quantum well give rise to spatial fluctuations in the dielectric response of the system while the large exciton resonance causes strong enhancement of scattering. The homogeneous linewidth was calculated across the exciton resonance. The technique is compared with the dephasing and hole-burning techniques more commonly used in homogeneous linewidth measurements.
Surface Review and Letters, 2002
Layers of 6 and 16 Cd-Te-Zn-Te periods were grown by atomic layer epitaxy (ALE) within ZnTe thin films. Different samples were grown at substrate temperatures of 260 and 290°C. Information about the kinetics of growth and surface reconstruction during the ALE growth of CdTe and ZnTe films, and Cd-Te-Zn-Te periods was obtained by means of reflection high-energy electron diffraction (RHEED) experiments and through the analysis of the temporal behavior of the intensities of several features of the RHEED patterns. The photoluminescence of the sample grown at 260°C presents two narrow and intense peaks corresponding to emission from quantum wells (QWs). However, the spectrum of the samples grown at 290°C does not show any feature associated with QWs, the spectrum resembling that of a ZnTe film. Cd replacement by Zn atoms explains the absence of the CdZnTe QWs at 290°C and a lower Cd content than expected at 260°C. The replacement of Cd atoms by Zn atoms in the CdTe surface was clearly demonstrated by Auger experiments.
Time-resolved luminescence studies in ann-typeZn1−xCdxSe/ZnSySe1−yquantum well
Physical Review B, 1996
The recombination processes in an n-type Zn 1-x Cd x Se/ZnS y Se 1Ϫy quantum well are investigated by timeresolved photoluminescence measurements. The combined analysis of the luminescence decay time and intensity yields the temperature dependence of the radiative and nonradiative recombination time. The quantum efficiency at a low temperature of 8 K is close to unity and the nonradiative recombination rate increases as the temperature is raised. The large effective radiative recombination coefficient of 1.4ϫ10 Ϫ9 cm 3 /s at 300 K is attributed to excitonic enhancement, even at 300 K.
Le Journal de Physique IV, 1993
A comparative luminescence and magneto-transmission study is made of donor bound excitons DOX and negatively charged excitons X-in planar doped CdTeICdl-,&Te quantum wells of IWA width. AS the dopant plane is removed from the well centres to 450A distance in the barriers, DOX evolves continuously into an X-species weakly localised in random potential fluctuations. The exciton localisation energy in DOX transforms into the second electron's binding energy in X-.
Excitons as a probe of interface morphology in Cd(Zn)Se/ZnSe heterostructures
Applied Surface Science, 2000
. We present studies of the excitonic spectrum in superlattices SLs of CdSe insertions in a ZnSe matrix aimed at elucidating the CdSerZnSe interface morphology. The experimental photoluminescence excitation spectra are compared with the results of variational exciton calculations performed within the effective mass approximation. The shape of the Ž . average vertical along the SL growth axis distribution of CdSe within each insertion, used in the calculations, was obtained Ž . from a theoretical simulation of X-ray diffraction XRD rocking curves measured in the same samples. The results indicate Ž . that the thinnest layers are graded composition ZnCdSe quantum wells QWs , generally homogeneous in the layer planes, Ž . whereas flat islands enriched by Cd appear at the CdSe nominal thickness larger than 0.5-0.6 monolayer ML . q
Journal of Applied Physics, 2006
By controlled annealing of small ZnSe mesas with embedded CdZnSe quantum dots ͑QDs͒ at considerably low temperatures, significant changes of the QD luminescence have been observed. To investigate the spectral evolution of single exciton lines several thermal annealing steps were performed successively, and large energy shifts of single exciton ͑X͒ lines due to annealing were traced. In annealed QDs the biexciton ͑XX͒ emission is drastically enhanced. Biexciton binding energies less than 10 meV were recorded for the thermally annealed CdZnSe QDs, indicating a considerable change in the QD confinement. The pronounced energy shifts of the QD luminescence is attributed to the Cd-Zn interdiffusion between the CdZnSe QDs and the surrounding ZnSe matrix. In small mesas interdiffusion activation energy ͑E A ͒ of less than 1 eV was determined. This value of E A is half of that recorded for the Cd-Zn interdiffusion in large QD ensembles, indicating that the sidewalls of the etched mesas play an important role in the observed diffusion process.
Optical- and acoustical-phonon-assisted hopping of localized excitons in CdTe/ZnTe quantum wells
Physical Review B, 1992
Interaction with both acoustical as well as optical phonons contributes to the relaxation of excitons in tail states of coherently strained CdTe/ZnTe quantum wells. The contribution of acoustical phonons is most important in the thinnest well of 1.8 monolayers. Hopping down, which involves the emission of acoustic phonons, leads to a redshift of the luminescence band of about 10 meV within the first 200 ps after excitation. A comparison of the experimental data with results of a quantitative theory allows us to evaluate the concentration of localized states involved in the relaxation process.
Optical spectroscopy of single Cd0.6Zn0.4Te/ZnTe quantum dots on Si substrate
Thin Solid Films, 2011
a b s t r a c t Keywords: Cadmium zinc telluride II-VI compound semiconductors Quantum dots Si substrate Single dot spectroscopy Photoluminescence Molecular beam epitaxy Microphotoluminescence (μ-PL) measurements were carried out to investigate the optical properties of single Cd 0.6 Zn 0.4 Te/ZnTe quantum dots (QDs) grown on Si substrate by using molecular beam epitaxy. The high quality of single Cd 0.6 Zn 0.4 Te/ZnTe QDs is witnessed by resolution-limited emission, negligible background and absence of measurable spectral jitter or blinking. Polarization-dependent and powerdependent μ-PL spectroscopy measurements were performed to identify the exciton, the biexciton, and the charged exciton in the emission spectra of single QDs. Furthermore a weak linearly polarized line is observed on the low energy side of the neutral exciton and is ascribed to dark exciton recombination.
Optical properties versus growth conditions of CdTe submonolayers inserted in ZnTe quantum wells
Physical Review B, 1998
Standard and piezomodulated optical spectroscopy is performed on ZnTe quantum wells embedding integer and fractional monolayers of CdTe. The samples, grown in a molecular-beam-epitaxy setup on the ͑001͒ surface of ZnTe substrates, all basically consist of 120-ML-wide ZnTe/͑Zn,Mg͒Te quantum wells, and some of them contain five equally spaced full or half-monolayers of CdTe, producing monomolecular islands of CdTe ''buried'' in the wide host ZnTe well. The latter behave as efficient recombination centers for excitons. In order to change the size and the configuration of the islands, various growth parameters have been changed between the different samples, e.g., the growth process ͑molecular-beam epitaxy of binaries or ternaries, or atomic-layer epitaxy͒ or the temperature. From spectroscopic measurements, the influence of these parameters is analyzed in detail, in terms of the size of the islands and of their in-plane spacing, or of the vertical correlation between these islands. The internal strain state of the CdTe insertions and the overall photoluminescence efficiency are also studied versus growth conditions. ͓S0163-1829͑98͒01047-9͔
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.
References (9)
- D. Lee, A.M. Johnson, J.E. Zucker, R.D. Feldman and R.F. Austin, J. Appl. Phys. 69 (1991) 6722.
- R.P. Stanley, B.J. Hawdon, J. Hegarty, R.D. Feldman and R.F. Austin, Appl. Phys. Lett. 58 (1991) 2972.
- R.P. Stanley, J. Hegarty, R. Fischer, J. Feldmann, E.O. Gobel, R.D. Feldmann and R.F. Austin, Phys. Rev.
- Lett. 67 (1991) 128.
- R.P. Stanley, J. Hegarty, R. Fischer, J. Feldmann, E.O. Gobel, R.D. Feldman and R.F. Austin, J. Crystal Growth 101 (1990) 683.
- J.P. Doran, J.F. Donegan, J. Hegarty, R.D. Feldman and R.F. Austin, Solid State Commun. 81 (1992) 801.
- J.P. Doran, J.F. Donegan, R.P. Stanley, J. Hegarty, R.D. Feldman and R.F. Austin, J. Crystal Growth 117 (1992) 465.
- N. Pelekonas, J. Ding, A.V. Nurmikko, H. Luo, N. Samarth and J.K. Furdyna, Technical Digest of OSA Topical Meeting on Quantum Optoelectronics, Salt Lake City (1991) p. 4.
- J. Feldmann, G. Peter, E.O. Gobel, P. Dawson, K. Moore, C. Foxon and R.J. Elliot, Phys. Rev. Lett. 59 (1987) 2337.
Related papers
Quantum-confined Stark effect on spatially indirect excitons in CdTe/CdxZn1−xTe quantum wells
Physical Review B, 1997
The quantum-confined Stark effect is studied in the mixed type-I/type-II CdTe/Cd x Zn 1Ϫx Te strained heterostructures. The type-II nature of the light-hole excitons is unambiguously confirmed by the blueshift observed under increasing electric field, in good agreement with calculations. On the other hand, the heavy-hole excitons are redshifted as expected for type-I excitons. The peculiar valence-band alignment, resulting from the sign reversal of the strain between the wells and the barriers, is used to detect the electric-field induced mixing of LH 1 and HH 2 confined hole states. An accurate value for the long-disputed chemical valence-band offset of CdTe/ZnTe system is extracted as ⌬E V ϭ(11Ϯ3)% of the band-gap difference between unstrained CdTe and ZnTe materials. ͓S0163-1829͑96͒06835-X͔
Relaxation of excitons in coherently strained CdTe/ZnTe quantum wells
Physical Review B, 1991
The relaxation kinetics of photogenerated excitons have been investigated in coherently strained CdTe/ZnTe quantum wells. Picosecond time-resolved luminescence spectra clearly display several replicas of the excitation pump due to the relaxation of photogenerated excitons in the CdTe well assisted by the emission of optical phonons. The luminescence replicas merge into a single broadband at a time typically larger than 300 ps, revealing spatial diAusion of excitons in the well. We study the gradual localization of photogenerated excitons from the decay of the hot luminescence.
Spectroscopy of donors and donor-bound excitons in CdTe/Cd1−xZnxTe multiple quantum wells
Materials Science and Engineering: B, 1993
Optical spectra for D°X (excitons bound by neutral donors) are identified in emission and absorption spectra of CdTe/ Cdl-xZnxTe multiple quantum wells that were planar-doped with indium. The effect of quantum confinement on the exciton localization energy is measured as a function of well width. The ls-' 2p + transition of neutral donors is studied by faroIR magnetoabsorption spectroscopy and shows no evidence for segregation of the dopant atoms.
Resonant Raman scattering mediated by excitons in CdTe/CdZnTe multiple quantum wells
Journal of Luminescence, 1992
The low temperature. LO-phonon Raman scattering is studied in two types of Cfle/Cd~.~Zn~~Te multiple quantum wells: types I and H. The resonance profile has peaks at the energy for which the maiming beam is at the lowest exciton bands, and much stronger peaks at the outgoing beam resonance. This observation is explained by the admixture of exciton states with large in-plane K -vectors with the K so exciton state and by the small dynamic damping of the excitons. The electronic structure of the system suggests that the admixture is due to hole scattering by alloy fluctuations in the CdZnTe barriers.
Optical properties of Cd1−Zn Te crystals grown by temperature gradient solution growth
Materials Chemistry and Physics, 2003
Cd 1-x Zn x Te crystals were grown by the temperature gradient solution growth (TGSG). Optical properties of the Cd 1-x Zn x Te crystals were investigated by the photoluminescence (PL) spectroscopy. The full width at half maximum (FWHM) of 11 meV for the near band edge PL was obtained. The temperature dependent broadening of the PL line-width was fitted by the acoustic phonon, longitudinal optical phonon, and impurity interaction parameters. Defect radiative density is as low as 0.002.
Superlattices and Microstructures, 1998
Integer or half monolayers of CdTe have been deposited, every 20 monolayers, in 120monolayer wide ZnTe/(Zn,Mg)Te quantum wells, by molecular beam epitaxy or atomic layer epitaxy on nominal (001) surfaces of ZnTe substrates. Low-temperature direct and piezomodulated reflectivity as well as C.W. and time-resolved photoluminescence have been taken from these samples. By comparison of samples grown in slightly different ways, we conclude that fractional CdTe layers, separated by a few ZnTe monolayers, grown in a Zn-rich environment, tend to grow in an ordered way: successive CdTe islands are stacked in vertical columns separated by columnar 'voids' of pure ZnTe. This behavior is the opposite of the staggered lineup of ZnTe islands in CdTe-(Cd,Zn)Te quantum wells, grown on Cd-rich substrates, recently observed by similar experimental techniques. Both behaviors are tentatively explained in terms of the relative stiffnesses of the materials of the inserts and of the matrix.
Charged excitons trapped on monomolecular CdTe islands in wide ZnTe-(Zn,Mg)Te quantum wells
Physical Review B, 1998
Optical spectroscopy at Tϭ2 K reveals systematically a low-energy companion to the features of heavy-and light-hole excitons localized on CdTe 1-ML-high islands, buried in wide ZnTe/͑Zn,Mg͒ Te quantum wells. These transitions are assigned to a negatively charged excitonic complex ͑trion͒ from magnetoreflectance and photoluminescence results. A mechanism of formation of the trion is proposed. A clear correlation is found between the exciton energies, which depend on the size and strain of the islands, and the trion binding energy, which varies between 1 and 3 meV. ͓S0163-1829͑98͒02248-6͔
Radiative recombination of indirect exciton in type-II ZnSeTe/ZnSe multiple quantum wells
Journal of Luminescence, 2011
The tunability of the emission energy, oscillator strength and photoluminescence (PL) efficiency by varying the well thickness and excitation density was demonstrated in the ZnSe 0.8 Te 0.2 /ZnSe multiple quantum wells. A significant blueshift about 260 meV of the PL peak energy was observed as the well width decreased from 5 to 1 nm. An extraordinary long lifetime (300 ns) of the recombination for the widest sample was detected. The binding energy of the indirect excitons is determined as 12 meV for the thinnest sample. The reduction of PL efficiency by thermal energy is greatly suppressed by employing a high excitation power.
Effect of structural imperfections on luminescence of ZnCdSe/ZnSe quantum wells
Journal of Alloys and Compounds, 2004
The structural and luminescence properties of Zn 1−x Cd x Se/ZnSe multi-quantum well (MQW) structures with high molar fraction of cadmium (30-50%) and wide ZnSe barriers (50, 100 and 500 nm) grown by molecular beam epitaxy (MBE) have been investigated by high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL) methods. It is shown that the fluctuations of composition within the quantum well layer determine the full-width at half maximum (FWHM) of the QW photoluminescence peak. The unusual polarization characteristics of this photoluminescence have been observed. The emission peak in the edge geometry is strongly polarized perpendicularly to the QW plane. This effect is ascribed to the localization of the ground-state heavy-hole-like excitons in the regions with increased cadmium content.