Excitation intensity dependence of photoluminescence spectra of SiGe quantum dots grown on prepatterned Si substrates: Evidence for biexcitonic transition

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Authors

KLENOVSKÝ Petr BREHM Moritz KŘÁPEK Vlastimil LAUSECKER Elisabeth MUNZAR Dominik HACKL Florian STEINER Hubert FROMHERZ Thomas BAUER Günther HUMLÍČEK Josef

Year of publication 2012
Type Article in Periodical
Magazine / Source Physical Review B
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://link.aps.org/doi/10.1103/PhysRevB.86.115305
Doi http://dx.doi.org/10.1103/PhysRevB.86.115305
Field Solid matter physics and magnetism
Keywords quantum dots; SiGe; photoluminescence; excitonic structure; biexciton
Description The pumping intensity (I) dependence of the photoluminescence (PL) spectra of perfectly laterally two-dimensionally ordered SiGe quantum dots on Si(001) substrates was studied. The PL results from recombinations of holes localized in the SiGe quantum dots and electrons localized due to the strain field in the surrounding Si matrix. The analysis of the spectra revealed several distinct bands, attributed to phonon-assisted recombination and no-phonon recombination of the excitonic ground state and of the excited excitonic states, which all exhibit a linear I dependence of the PL intensity. At approximately I larger than 3 W cm-2, additional bands with a nearly quadratic I dependence appear in the PL spectra, resulting from biexcitonic transitions. These emerging PL contributions shift the composite no-phonon PL band of the SiGe quantum dots to higher energies. The experimentally obtained energies of the no-phonon transitions are in good agreement with the exciton and biexciton energies calculated using the envelope function approximation and the configuration interaction method.
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