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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

RHEED pattern of GaAs (100) surface after Ga-assisted deoxidation and subsequent quick anneal under As4 atmosphere. The usual 2 × 4 reconstruction is observed indicating the successful removal of the native oxide.
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Figure 2: RHEED pattern of GaAs (100) surface after Ga-assisted deoxidation and subsequent quick anneal under As4 atmosphere. The usual 2 × 4 reconstruction is observed indicating the successful removal of the native oxide.

Mentions: After reintroducing the pre-structured sample into the MBE chamber, the native oxide has to be removed prior to regrowth. The Ga-assisted deoxidation is advantageous as it is performed at moderate temperatures and thus inhibits additional surface pitting. Since only Ga is provided this gentle deoxidation method does not introduce electronic defects at the surface. Also, any excess Ga on the surface will be incorporated in the subsequent GaAs BL. The surface is monitored by means of in situ reflection high energy electron diffraction (RHEED). Diffuse and faint main streaks of the 2 × 4 reconstruction evolve into a clear full 2 × 4 reconstruction pattern after deposition of about 8 ML of Ga. The RHEED pattern of a pre-structured sample after oxide removal is shown in Figure 2. InAs QDs are grown on top of a 16 nm GaAs BL. Mainly double dot nucleation is observed. One possible reason for that phenomenon is a change in hole shape during BL growth with the hole developing into two separate holes with increasing BL thickness [8]. A sample with site-selective InAs QDs is shown in Figure 3. The upper linescan of Figure 3b clearly reveals the double dot feature. Moreover, some defects are apparent in the AFM images as well. Figure 3a shows larger areas of defects (white circles) and Figure 3b contains smaller defect holes, as visualized by the lower linescan. Their origin is further investigated in the following section.


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)

RHEED pattern of GaAs (100) surface after Ga-assisted deoxidation and subsequent quick anneal under As4 atmosphere. The usual 2 × 4 reconstruction is observed indicating the successful removal of the native oxide.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: RHEED pattern of GaAs (100) surface after Ga-assisted deoxidation and subsequent quick anneal under As4 atmosphere. The usual 2 × 4 reconstruction is observed indicating the successful removal of the native oxide.
Mentions: After reintroducing the pre-structured sample into the MBE chamber, the native oxide has to be removed prior to regrowth. The Ga-assisted deoxidation is advantageous as it is performed at moderate temperatures and thus inhibits additional surface pitting. Since only Ga is provided this gentle deoxidation method does not introduce electronic defects at the surface. Also, any excess Ga on the surface will be incorporated in the subsequent GaAs BL. The surface is monitored by means of in situ reflection high energy electron diffraction (RHEED). Diffuse and faint main streaks of the 2 × 4 reconstruction evolve into a clear full 2 × 4 reconstruction pattern after deposition of about 8 ML of Ga. The RHEED pattern of a pre-structured sample after oxide removal is shown in Figure 2. InAs QDs are grown on top of a 16 nm GaAs BL. Mainly double dot nucleation is observed. One possible reason for that phenomenon is a change in hole shape during BL growth with the hole developing into two separate holes with increasing BL thickness [8]. A sample with site-selective InAs QDs is shown in Figure 3. The upper linescan of Figure 3b clearly reveals the double dot feature. Moreover, some defects are apparent in the AFM images as well. Figure 3a shows larger areas of defects (white circles) and Figure 3b contains smaller defect holes, as visualized by the lower linescan. Their origin is further investigated in the following section.

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