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Optical absorption in highly strained Ge/SiGe quantum wells: the role of →Δ scattering

Optical absorption in highly strained Ge/SiGe quantum wells: the role of →Δ scattering
Optical absorption in highly strained Ge/SiGe quantum wells: the role of →Δ scattering
We report the observation of the quantum-confined Stark effect in Ge/SiGe multiple quantum well heterostructures grown on Si0.22Ge0.78 virtual substrates. The large compressive strain in the Ge quantum well layers caused by the lattice mismatch with the virtual substrate results in a blue shift of the direct absorption edge, as well as a reduction in the Gamma-valley scattering lifetime because of strain-induced splittings of the conduction band valleys. We investigate theoretically the Gamma-valley carrier lifetimes by evaluating the Gamma-to-Delta and Gamma-to-Delta scattering rates in strained Ge/SiGe semiconductor heterostructures. These scattering rates are used to determine the lifetime broadening of excitonic peaks and the indirect absorption in simulated absorption spectra, which are compared with measured absorption spectra for quantum well structures with systematically varied dimensions. We find that Gamma-to-Delta scattering is significant in compressively strained Ge quantum wells and that the Gamma-valley electron lifetime is less than 50 fs in the highly strained structures reported here, where Gamma-to-Delta scattering accounted for approximately half of the total scattering rate.
carrier lifetime, conduction bands, elemental semiconcuctors, excitons, germanium, infrared spectra, quantum confined stark effect, semiconductor quantum wells, spectral line shift
0021-8979
Lever, L.
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Ikonić, Z.
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Valavanis, A.
add56198-2315-49f9-844f-2ac9c25dee43
Kelsall, R.W.
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Myronov, M.
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Leadley, D.R.
02284a16-afed-4fa7-8507-a3673e56647f
Hu, Y.
38fe48b3-1609-4834-ad54-dc823e3a98b3
Owens, N.
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Gardes, F.Y.
7a49fc6d-dade-4099-b016-c60737cb5bb2
Reed, G.T.
ca08dd60-c072-4d7d-b254-75714d570139
Lever, L.
a0f9718b-94e2-4c75-92f5-5cd3915e80b5
Ikonić, Z.
11c7ebda-4910-4d8a-9178-06ba973a1eb1
Valavanis, A.
add56198-2315-49f9-844f-2ac9c25dee43
Kelsall, R.W.
82f442cd-66f0-4902-89af-a2d126e2d0c8
Myronov, M.
4e4a5ce0-a433-4654-a875-e939c99d0ffe
Leadley, D.R.
02284a16-afed-4fa7-8507-a3673e56647f
Hu, Y.
38fe48b3-1609-4834-ad54-dc823e3a98b3
Owens, N.
d0c8b90a-322e-4a9f-b6fb-741450fb1ce3
Gardes, F.Y.
7a49fc6d-dade-4099-b016-c60737cb5bb2
Reed, G.T.
ca08dd60-c072-4d7d-b254-75714d570139

Lever, L., Ikonić, Z., Valavanis, A., Kelsall, R.W., Myronov, M., Leadley, D.R., Hu, Y., Owens, N., Gardes, F.Y. and Reed, G.T. (2012) Optical absorption in highly strained Ge/SiGe quantum wells: the role of →Δ scattering. Journal of Applied Physics, 112 (12). (doi:10.1063/1.4768935).

Record type: Article

Abstract

We report the observation of the quantum-confined Stark effect in Ge/SiGe multiple quantum well heterostructures grown on Si0.22Ge0.78 virtual substrates. The large compressive strain in the Ge quantum well layers caused by the lattice mismatch with the virtual substrate results in a blue shift of the direct absorption edge, as well as a reduction in the Gamma-valley scattering lifetime because of strain-induced splittings of the conduction band valleys. We investigate theoretically the Gamma-valley carrier lifetimes by evaluating the Gamma-to-Delta and Gamma-to-Delta scattering rates in strained Ge/SiGe semiconductor heterostructures. These scattering rates are used to determine the lifetime broadening of excitonic peaks and the indirect absorption in simulated absorption spectra, which are compared with measured absorption spectra for quantum well structures with systematically varied dimensions. We find that Gamma-to-Delta scattering is significant in compressively strained Ge quantum wells and that the Gamma-valley electron lifetime is less than 50 fs in the highly strained structures reported here, where Gamma-to-Delta scattering accounted for approximately half of the total scattering rate.

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More information

Published date: 15 December 2012
Keywords: carrier lifetime, conduction bands, elemental semiconcuctors, excitons, germanium, infrared spectra, quantum confined stark effect, semiconductor quantum wells, spectral line shift
Organisations: Optoelectronics Research Centre, Nanoelectronics and Nanotechnology

Identifiers

Local EPrints ID: 356037
URI: https://eprints.soton.ac.uk/id/eprint/356037
ISSN: 0021-8979
PURE UUID: b94feae3-34b6-459e-917e-795753f6ce36

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Date deposited: 10 Sep 2013 11:13
Last modified: 25 Jul 2019 16:31

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Contributors

Author: L. Lever
Author: Z. Ikonić
Author: A. Valavanis
Author: R.W. Kelsall
Author: M. Myronov
Author: D.R. Leadley
Author: Y. Hu
Author: N. Owens
Author: F.Y. Gardes
Author: G.T. Reed

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