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Excitation Intensity Driven PL Shifts of SiGe Islands on Patterned and Planar Si(001) Substrates: Evidence for Ge-rich Dots in Islands.

Brehm M, Grydlik M, Hackl F, Lausecker E, Fromherz T, Bauer G - Nanoscale Res Lett (2010)

Bottom Line: For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber.We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra.The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Semiconductor and Solid State Physics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria.

ABSTRACT
For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber. We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra. The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.

No MeSH data available.


Related in: MedlinePlus

PL spectra for 16 mW/cm2 <Pexc < 244.3 W/cm2 measured for islands on a pit-patterned substrate. Only a minor shift of the island PL with increasing Pexc is observed. A new peak of unknown origin appears for Pexc ≥ 18 W/cm2 at 898 meV. The detector cut-off at 0.77 eV is indicated by the dashed line. The spectra are shifted vertically for clarity
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Figure 2: PL spectra for 16 mW/cm2 <Pexc < 244.3 W/cm2 measured for islands on a pit-patterned substrate. Only a minor shift of the island PL with increasing Pexc is observed. A new peak of unknown origin appears for Pexc ≥ 18 W/cm2 at 898 meV. The detector cut-off at 0.77 eV is indicated by the dashed line. The spectra are shifted vertically for clarity

Mentions: In Fig. 2, the PL spectra of the Ge WL and islands grown on the pit-patterned Si substrate were measured as a function of Pexc that was varied between 16 mW/cm2 and 244.3 W/cm2. For Pexc = 16 mW/cm2 (blue spectrum, bottom), the island NP peak at 0.882 eV and the island TO-phonon peak at 0.825 eV can be clearly observed. For Pexc > 91 mW/cm2, peaks corresponding to the Si bulk phonon replica arise. Additionally, a weak signal between 0.99 and 1.075 eV is attributed to the Ge WL between the islands. For Pexc > 18.21 mW/cm2, we observe the formation of so-called electron-hole droplets correlated to the Si bulk phonon replica [16]. Only a small blue-shift of the island NP-PL from 0.882 to 0.9 eV is observed by increasing Pexc from 16 mW/cm2 to 244 W/cm2. The peak at 0.898 eV that appears for Pexc > 3.3 W/cm2 is of unknown origin.


Excitation Intensity Driven PL Shifts of SiGe Islands on Patterned and Planar Si(001) Substrates: Evidence for Ge-rich Dots in Islands.

Brehm M, Grydlik M, Hackl F, Lausecker E, Fromherz T, Bauer G - Nanoscale Res Lett (2010)

PL spectra for 16 mW/cm2 <Pexc < 244.3 W/cm2 measured for islands on a pit-patterned substrate. Only a minor shift of the island PL with increasing Pexc is observed. A new peak of unknown origin appears for Pexc ≥ 18 W/cm2 at 898 meV. The detector cut-off at 0.77 eV is indicated by the dashed line. The spectra are shifted vertically for clarity
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2991224&req=5

Figure 2: PL spectra for 16 mW/cm2 <Pexc < 244.3 W/cm2 measured for islands on a pit-patterned substrate. Only a minor shift of the island PL with increasing Pexc is observed. A new peak of unknown origin appears for Pexc ≥ 18 W/cm2 at 898 meV. The detector cut-off at 0.77 eV is indicated by the dashed line. The spectra are shifted vertically for clarity
Mentions: In Fig. 2, the PL spectra of the Ge WL and islands grown on the pit-patterned Si substrate were measured as a function of Pexc that was varied between 16 mW/cm2 and 244.3 W/cm2. For Pexc = 16 mW/cm2 (blue spectrum, bottom), the island NP peak at 0.882 eV and the island TO-phonon peak at 0.825 eV can be clearly observed. For Pexc > 91 mW/cm2, peaks corresponding to the Si bulk phonon replica arise. Additionally, a weak signal between 0.99 and 1.075 eV is attributed to the Ge WL between the islands. For Pexc > 18.21 mW/cm2, we observe the formation of so-called electron-hole droplets correlated to the Si bulk phonon replica [16]. Only a small blue-shift of the island NP-PL from 0.882 to 0.9 eV is observed by increasing Pexc from 16 mW/cm2 to 244 W/cm2. The peak at 0.898 eV that appears for Pexc > 3.3 W/cm2 is of unknown origin.

Bottom Line: For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber.We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra.The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Semiconductor and Solid State Physics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria.

ABSTRACT
For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber. We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra. The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.

No MeSH data available.


Related in: MedlinePlus