Thermodynamics and Diffusion of Free Trions in Mixed Type GaAs/AlAs Quantum Wells

AbstractAn emission line which depends on the simultaneous presence of excitons and < 2×1010 cm−2 free photoexcited electrons in a 20 nm quantum well is shown to be due to the recombination of free negatively charged excitons ( “trions”). The binding energy is 1.3 meV and the lifetime is 1/4 that of the exciton. The increase in the radiative decay times of excitons and trions with increasing bath temperature is consistent with that of free particles. More directly, from time- and spatially-resolved measurements, we find that trions are localized at 5 K, and with increasing bath temperature both excitons and trions become mobile. The diffusivity of trions and excitons increases linearly with bath temperature, and at 10 K, the trion diffusivity is found to be factor of two lower than the exciton diffusivity. Our results are the first direct experimental evidence for free trions in GaAs quantum wells.

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Interband transitions dependent on indium concentration in Ga1−xInxAs/GaAs asymmetric triple quantum wells

International Journal of Modern Physics B ◽

10.1142/s0217979218500522 ◽

2018 ◽

Vol 32 (05) ◽

pp. 1850052 ◽

Cited By ~ 4

Author(s):

B. O. Alaydin ◽

E. Ozturk ◽

S. Elagoz

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Electronic Properties ◽

Radiative Decay ◽

Interband Transition ◽

Energy Levels ◽

Oscillator Strengths ◽

Quantum Well Structures ◽

Transition Energies ◽

Decay Times

In this paper, the optical and electronic properties of asymmetric triple quantum well (ATQW) structures are studied depending on the indium concentrations while quantum well (QW) thicknesses and barrier widths are kept constant. Calculation of electronic properties are done within the framework of the effective mass approximation. The indium concentrations in left quantum well (LQW) and right quantum well (RQW) are varied in order to see the change of energy levels. Then, interband transition energies, wavelengths, oscillator strengths and radiative decay times are determined depending on barrier height. The scope of this study, for the first time in the literature, covers converged interband transition energies for the asymmetric quantum well structures.

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Growth Evolution of (Zn,Cd)Se Quantum Dots Deduced from Spatially Resolved Structural and Optical Characterization

MRS Proceedings ◽

10.1557/proc-571-325 ◽

1999 ◽

Vol 571 ◽

Cited By ~ 1

Author(s):

K. Leonard ◽

D. Hommel ◽

A. Stockmann ◽

H. Selke ◽

J. Seufert ◽

...

Keyword(s):

Quantum Dots ◽

Quantum Wells ◽

Three Dimensional ◽

High Energy ◽

Growth Direction ◽

Growth Mode ◽

Gradual Transition ◽

Mode Transition ◽

Spatially Resolved ◽

Composition Fluctuations

ABSTRACTThe growth mode of CdSe layers grown by migration enhanced epitaxy between ZnSe barriers has been investigated. In situ reflection high-energy electron diffraction shows a gradual transition to a three-dimensional growth mode which, however, is not accompanied by a change of the surface lattice constant. High-resolution transmission electron micrographs reveal a strong Cd diffusion, leading to ternary ZnCdSe quantum wells. Furthermore. composition fluctuations perpendicular to the growth direction on a nanometer scale are found already prior to the beginning of the growth mode transition. In the case of heterostructures containing a CdSe layer that has undergone the growth mode transition, micrographs show Cd-rich quantum dots with diameters of around 8 nm and heights of around 1.5 nm within a ternary quantum well. By spatially resolved photoluminescence the emission from single quantum dots could be observed. The polarization dependence of the emission from single dots indicates an asymmetric shape of the dots with certain preferential orientations along the [110] and [110] directions.

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Energy relaxation during hot-exciton transport in quantum wells: Direct observation by spatially resolved phonon-sideband spectroscopy

Applied Physics Letters ◽

10.1063/1.1512819 ◽

2002 ◽

Vol 81 (15) ◽

pp. 2794-2796 ◽

Cited By ~ 20

Author(s):

Hui Zhao ◽

Sebastian Moehl ◽

Heinz Kalt

Keyword(s):

Quantum Wells ◽

Direct Observation ◽

Energy Relaxation ◽

Spatially Resolved ◽

Exciton Transport

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Indirect transitions between barrier (X) electrons and two-dimensional hole gas in mixed type I - type II quantum wells

Springer Proceedings in Physics - Proceedings of the 25th International Conference on the Physics of Semiconductors Part I ◽

10.1007/978-3-642-59484-7_270 ◽

2001 ◽

pp. 571-572

Author(s):

R. Guliamov ◽

E. Lifshitz ◽

E. Cohen ◽

Arza Ron ◽

L. N. Pfeiffer

Keyword(s):

Quantum Wells ◽

Mixed Type ◽

Type I ◽

Type Ii ◽

Two Dimensional ◽

Type Ii Quantum Wells

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On radiative and non-radiative decay times in the weak coupling limit

Physica B+C ◽

10.1016/0378-4363(84)90117-7 ◽

1984 ◽

Vol 123 (2) ◽

pp. 131-155 ◽

Cited By ~ 34

Author(s):

M.F.H. Schuurmans ◽

J.M.F. van Dijk

Keyword(s):

Weak Coupling ◽

Radiative Decay ◽

Weak Coupling Limit ◽

Decay Times

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Spatially resolved optical emission of cubic GaN/AlN multi-quantum well structures

MRS Proceedings ◽

10.1557/opl.2014.944 ◽

2014 ◽

Vol 1736 ◽

Cited By ~ 1

Author(s):

D.J. As ◽

R. Kemper ◽

C. Mietze ◽

T. Wecker ◽

J.K.N. Lindner ◽

...

Keyword(s):

Optical Properties ◽

Low Temperature ◽

Film Thickness ◽

Quantum Wells ◽

Emission Intensity ◽

Optical Emission ◽

Quantum Well Structures ◽

Spatially Resolved ◽

Scanning Transmission ◽

Cubic Gan

ABSTRACTIn this contribution we report on the optical properties of cubic AlN/GaN asymmetric multi quantum wells (MQW) structures on 3C-SiC/Si (001) substrates grown by radio-frequency plasma-assisted molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) and spatially resolved cathodoluminescence (CL) at room temperature and at low temperature are used to characterize the optical properties of the cubic AlN/GaN MQW structures. An increasing CL emission intensity with increasing film thickness due to the improved crystal quality was observed. This correlation can be directly connected to the reduction of the linewidth of x-ray rocking curves with increasing film thickness of the c-GaN films. Defects like stacking faults (SFs) on the {111} planes, which also can be considered as hexagonal inclusions in the cubic crystal matrix, lead to a decrease of the CL emission intensity. With low temperature CL line scans also monolayer fluctuations of the QWs have been detected and the observed transition energies agree well with solutions calculated using a one-dimensional (1D) Schrödinger-Poisson simulator.

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Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum wells

MRS Proceedings ◽

10.1557/proc-639-g6.12 ◽

2000 ◽

Vol 639 ◽

Author(s):

E.M. Goldys ◽

M. Godlewski ◽

M.R. Phillips ◽

A.A. Toropov

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Electric Fields ◽

Free Exciton ◽

Multiple Quantum Well ◽

Depth Profiling ◽

Multiple Quantum ◽

Recombination Mechanism ◽

Decay Times ◽

Piezoelectric Fields

ABSTRACTWe have examined multiple quantum well AlGaN/GaN structures with several quantum wells of varying widths. The structures had strain-free quantum wells and strained barriers. Strong piezoelectric fields in these structures led to a large red shift of the PL emission energies and long decay times were also observed. While the peak energies could be modelled using the effective mass approximation, the calculated free exciton radiative lifetimes were much shorter than those observed in experiments, indicating an alternative recombination mechanism, tentatively attributed to localised excitons. Cathodoluminescence depth profiling revealed an unusually small penetration range of electrons suggesting that electron-hole pairs preferentially remain within the multiple quantum well region due to the existing electric fields. Spatial fluctuations of the cathodoluminescence intensity were also observed.

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Strain-Induced Lateral Confinement of Carriers in Semiconductor Quantum Wells

MRS Proceedings ◽

10.1557/proc-144-245 ◽

1988 ◽

Vol 144 ◽

Author(s):

K. Kash ◽

R. Bhat ◽

Derek D. Mahoney ◽

J.M. Worlock ◽

P.S.D. Lin ◽

...

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Band Gap ◽

Red Shift ◽

Lateral Confinement ◽

Semiconductor Quantum Wells ◽

20 Nm ◽

Ingaas Quantum Well

ABSTRACTWe describe here an effort to provide lateral confinement of carriers within a continuous InGaAs quantum well by creating a pattern of strain in the well. A compressed InGaAsP layer overlying the quantum well and the InP barrier was patterned into submicron stressor wires by etching to within approximately 20 nm of the InP barrier. The relaxation of the compression at the edges of the quaternary stressors resulted in dilation of the quantum well material under their centers, thus lowering the band gap of the material, providing confinement for both electrons and holes there. We observed a red shift of the quantum well luminescence of 7 meV for 400 nm wide wires, evidence for the strain-induced lateral confinement. This is the first observation of a red-shifted band gap in submicron strain-confining structures.

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