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Spin relaxation in optically excited quantum wells

Spin relaxation in optically excited quantum wells
Spin relaxation in optically excited quantum wells
Interband excitation of GaAs with circularly polarised light produces a spin-polarised population of photoexcited carriers. The equilibrium degree of spin polarisation under cw excitation depends on the balance of spin relaxation and recombination rates, and can be monitored directly through the degree of polarisation of recombination radiation. We have measured the polarisation at 2 K of recombination radiation following band edge excitation for a variety of GaAs/AlGaAs quantum well samples of carrier content ranging from ≈ 108 cm -2 up to ≈ 2×1011 cm-2 in which values of recombination time have been measured, and have thereby determined the spin relaxation times. Two remarkable results emerge; (i) the spin relaxation time increases from 30 ps to > 8 ns as the carrier concentration is increased; and (ii) for degenerate n-type quantum wells the recombination radiation is close to 100% circularly polarised, there being strong evidence for a long spin memory in the electron Fermi sea. The first result may be explained in terms of a spin relaxation mechanism involving electron-hole exchange; the second has, at present, no clear theoretical interpretation.
0022-2313
208-210
Flinn, G.P.
a4fa86b9-2ba7-4d33-a75a-dc851166b079
Harley, R.T.
54613031-f60f-45f4-9b20-e49bcfd53b77
Snelling, M.J.
52851363-73f3-4934-a44b-77ae5f54b16a
Tropper, A.C.
f3505426-e0d5-4e91-aed3-aecdb44b393c
Kerr, T.M.
64f7681c-d5ab-42d2-84ba-c7e52e1f9767
Flinn, G.P.
a4fa86b9-2ba7-4d33-a75a-dc851166b079
Harley, R.T.
54613031-f60f-45f4-9b20-e49bcfd53b77
Snelling, M.J.
52851363-73f3-4934-a44b-77ae5f54b16a
Tropper, A.C.
f3505426-e0d5-4e91-aed3-aecdb44b393c
Kerr, T.M.
64f7681c-d5ab-42d2-84ba-c7e52e1f9767

Flinn, G.P., Harley, R.T., Snelling, M.J., Tropper, A.C. and Kerr, T.M. (1990) Spin relaxation in optically excited quantum wells. Journal of Luminescence, 45 (1-6), 208-210. (doi:10.1016/0022-2313(90)90147-4).

Record type: Article

Abstract

Interband excitation of GaAs with circularly polarised light produces a spin-polarised population of photoexcited carriers. The equilibrium degree of spin polarisation under cw excitation depends on the balance of spin relaxation and recombination rates, and can be monitored directly through the degree of polarisation of recombination radiation. We have measured the polarisation at 2 K of recombination radiation following band edge excitation for a variety of GaAs/AlGaAs quantum well samples of carrier content ranging from ≈ 108 cm -2 up to ≈ 2×1011 cm-2 in which values of recombination time have been measured, and have thereby determined the spin relaxation times. Two remarkable results emerge; (i) the spin relaxation time increases from 30 ps to > 8 ns as the carrier concentration is increased; and (ii) for degenerate n-type quantum wells the recombination radiation is close to 100% circularly polarised, there being strong evidence for a long spin memory in the electron Fermi sea. The first result may be explained in terms of a spin relaxation mechanism involving electron-hole exchange; the second has, at present, no clear theoretical interpretation.

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More information

Published date: 1990
Organisations: Optoelectronics Research Centre, Quantum, Light & Matter Group

Identifiers

Local EPrints ID: 78612
URI: https://eprints.soton.ac.uk/id/eprint/78612
ISSN: 0022-2313
PURE UUID: 88e31b60-5b76-4d53-b0b0-f1178887a4d5

Catalogue record

Date deposited: 11 Mar 2010
Last modified: 18 Jul 2018 16:31

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