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Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth.

Helfrich M, Gröger R, Förste A, Litvinov D, Gerthsen D, Schimmel T, Schaadt DM - Nanoscale Res Lett (2011)

Bottom Line: Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth.Successive cleaning steps were analyzed and optimized.A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination.

View Article: PubMed Central - HTML - PubMed

Affiliation: DFG-Center for Functional Nanostructures (CFN) and Institut für Angewandte Physik, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany. daniel.schaadt@kit.edu.

ABSTRACT
In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination.

No MeSH data available.


Related in: MedlinePlus

TEM image of burried defect hole originating from the regrowth interface.
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Figure 4: TEM image of burried defect hole originating from the regrowth interface.

Mentions: The additional defect holes were not defined during EBL and thus interfere with the attempt of deterministic QD positioning. The holes are less than 16 nm deep, which corresponds to the BL thickness. That is suggested by the linescan of Figure 3b. Therefore, the defect holes seem to originate from the regrowth interface. Further confirmation is given by TEM analysis of a capped sample. Figure 4 shows a TEM image of the profile of a defect hole, which was found on a pre-structured sample. The different layers of the structure are visible. In this case the defect hole develops from the pre-structured surface upward in the GaAs BL. A local change on that surface inhibits the proper regrowth of GaAs. InAs, however, then nucleates inside the hole, which is finally covered by the final capping layer. The GaAs sidewalls of the defect hole exhibit a curved shape with increasing thickness of the GaAs BL at larger distances from the hole. This implies that strain is accumulated at the surface of the GaAs BL facing the site where nucleation of GaAs is hindered.


Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth.

Helfrich M, Gröger R, Förste A, Litvinov D, Gerthsen D, Schimmel T, Schaadt DM - Nanoscale Res Lett (2011)

TEM image of burried defect hole originating from the regrowth interface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211268&req=5

Figure 4: TEM image of burried defect hole originating from the regrowth interface.
Mentions: The additional defect holes were not defined during EBL and thus interfere with the attempt of deterministic QD positioning. The holes are less than 16 nm deep, which corresponds to the BL thickness. That is suggested by the linescan of Figure 3b. Therefore, the defect holes seem to originate from the regrowth interface. Further confirmation is given by TEM analysis of a capped sample. Figure 4 shows a TEM image of the profile of a defect hole, which was found on a pre-structured sample. The different layers of the structure are visible. In this case the defect hole develops from the pre-structured surface upward in the GaAs BL. A local change on that surface inhibits the proper regrowth of GaAs. InAs, however, then nucleates inside the hole, which is finally covered by the final capping layer. The GaAs sidewalls of the defect hole exhibit a curved shape with increasing thickness of the GaAs BL at larger distances from the hole. This implies that strain is accumulated at the surface of the GaAs BL facing the site where nucleation of GaAs is hindered.

Bottom Line: Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth.Successive cleaning steps were analyzed and optimized.A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination.

View Article: PubMed Central - HTML - PubMed

Affiliation: DFG-Center for Functional Nanostructures (CFN) and Institut für Angewandte Physik, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany. daniel.schaadt@kit.edu.

ABSTRACT
In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination.

No MeSH data available.


Related in: MedlinePlus