Exciton luminescence in Si1-xGex/Si heterostructures grown by molecular beam epitaxy

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DOIResolve DOI: http://doi.org/10.1063/1.354628
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TypeArticle
Journal titleJournal of applied physics
ISSN0021-8979
Volume74
IssueAugust 4
Pages27902805; # of pages: 16
AbstractCoherent Si1−xGex alloys and multilayers synthesized by molecular beam epitaxy (MBE) on Si(100) substrates have been characterized by low-temperature photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). Phonon-resolved transitions originating from excitons bound to shallow impurities were observed in addition to a broad band of intense luminescence. The broad PL band was predominant when the alloy layer thickness was greater than 40–100 Å, depending on x and the strain energy density. The strength of the broad PL band was correlated with the areal density (up to ∼109 cm−2) of strain perturbations (local lattice dilation ∼15 Å in diameter) observed in plan-view TEM. Thinner alloy layers exhibited phonon-resolved PL spectra, similar to bulk material, but shifted in energy due to strain and hole quantum confinement. Photoluminescence excitation spectroscopy, external quantum efficiency, time-resolved PL decay, together with the power and temperature dependence of luminescence intensity, have been used to characterize Si1−xGex/Si heterostructures exhibiting both types of PL spectra. The role of MBE growth parameters in determining optical properties was investigated by changing the quantum well thickness and growth temperature. The transition from phonon-resolved, near-band-gap luminescence in thin layers to the broad PL band typical of thick layers is discussed in terms of a strain energy balance model which predicts a ‘‘transition thickness’’ which decreases with increase in x.
Publication date
LanguageEnglish
AffiliationNRC Institute for National Measurement Standards; National Research Council Canada
Peer reviewedNo
Identifier10011936
NRC number1157
NPARC number8899389
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Record identifier2cb7c6d2-a0e3-4997-86c2-e68fa4b11bf6
Record created2009-04-22
Record modified2016-05-09
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