Reduced exciton-exciton scattering in quantum wires

authored by: Wolfgang W. Ruhle, Michael Oestreich, Hebert Lage, Detlev Heitmann, Klaus Ploog
Abstract: The dynamics of free excitons in GaAs quantum-well wires (QWMs) is studied by means of time-resolved luminescence spectroscopy. The QWWs have been fabricated by holographic lithography and reactive-ion etching from a multiple quantum well consisting of 25 GaAs quantum wells (QWs) of 10.6-nm width sandwiched between 15.3-nm-wide AlGaAs barriers. The geometrical and active widths of the QWW are 150 and 60 nm, respectively, and the period is 280 nm. The wire cross section is therefore 10.6 nm (quantum number n) × 60 nm (quantum number m). The sample is kept at 10 K and is excited with picosecond pulses of a synchronously pumped dye laser. The photoluminescence is detected by a streak camera with temporal and spectral resolutions of 10 ps and 0.5 meV, respectively. The time-integrated photoluminescence and photoluminescence excitation spectra are depicted in Fig. 1(a). For a polarization E parallel to the wire direction, we observe only the n = 1, m = 1, and m = 3 excitons. Time-resolved experiments with resonant excitation into the m = 1 state reveal an unusually long nonthermal component exactly at the excitation energy [see Figs. 1(b) and 1(c)]. We define the thermalization time as the time at which this nonthermal component reaches 1/e of the initial strength. This thermalization time decreases from 80 ps for excitation in the n = 1, m = 1 ground subband, to 30 ps for excitation in the m = 3 subband, to values faster than our time resolution for higher excitation energies. The long-lived quasi-monoenergetic QWW photoluminescence for the low-energy excitation is a consequence of the absence of energy-changing exciton-exciton scattering channels in the lowest subband under strict conservation of energy and quasi-momentum k. For higher excitation energies, intersubband scattering and phonon emission decreases thermalization time. A decrease of thermalization time is also observed for increasing excitation density (>10² cm^-1) and increasing temperature (>15 K).
External Organisation(s): Max Planck Institute for Solid State Research (MPI-FKF)
Type: Conference contribution
Pages: 136-137
No. of pages: 2
Publication date: 1994
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: General Engineering

BibTeX

@inproceedings{7351b3098ad343caa23942624ef3cd86,
title = "Reduced exciton-exciton scattering in quantum wires",
abstract = "The dynamics of free excitons in GaAs quantum-well wires (QWMs) is studied by means of time-resolved luminescence spectroscopy. The QWWs have been fabricated by holographic lithography and reactive-ion etching from a multiple quantum well consisting of 25 GaAs quantum wells (QWs) of 10.6-nm width sandwiched between 15.3-nm-wide AlGaAs barriers. The geometrical and active widths of the QWW are 150 and 60 nm, respectively, and the period is 280 nm. The wire cross section is therefore 10.6 nm (quantum number n) × 60 nm (quantum number m). The sample is kept at 10 K and is excited with picosecond pulses of a synchronously pumped dye laser. The photoluminescence is detected by a streak camera with temporal and spectral resolutions of 10 ps and 0.5 meV, respectively. The time-integrated photoluminescence and photoluminescence excitation spectra are depicted in Fig. 1(a). For a polarization E parallel to the wire direction, we observe only the n = 1, m = 1, and m = 3 excitons. Time-resolved experiments with resonant excitation into the m = 1 state reveal an unusually long nonthermal component exactly at the excitation energy [see Figs. 1(b) and 1(c)]. We define the thermalization time as the time at which this nonthermal component reaches 1/e of the initial strength. This thermalization time decreases from 80 ps for excitation in the n = 1, m = 1 ground subband, to 30 ps for excitation in the m = 3 subband, to values faster than our time resolution for higher excitation energies. The long-lived quasi-monoenergetic QWW photoluminescence for the low-energy excitation is a consequence of the absence of energy-changing exciton-exciton scattering channels in the lowest subband under strict conservation of energy and quasi-momentum k. For higher excitation energies, intersubband scattering and phonon emission decreases thermalization time. A decrease of thermalization time is also observed for increasing excitation density (>102 cm-1) and increasing temperature (>15 K).",
author = "Ruhle, {Wolfgang W.} and Michael Oestreich and Hebert Lage and Detlev Heitmann and Klaus Ploog",
note = "Funding information: We gratefully acknowledge the expert technical assistance of K. Rother and the partial support by the Bundesministerium f{\"u}r Forschung und Tech-nologie of Germany.; 21st International Quantum Electronics Conference (IQEC'94) ; Conference date: 08-05-1994 Through 13-05-1994",
year = "1994",
language = "English",
isbn = "0780319737",
series = "Proceedings of the International Quantum Electronics Conference (IQEC'94)",
publisher = "Publ by IEEE",
pages = "136--137",
booktitle = "Proceedings of the International Quantum Electronics Conference (IQEC'94)",
}