GaAs cap layer growth and In-segregation effects on self-assembled InAs-quantum dots monitored by optical techniques

Steimetz, E.; Wehnert, Timon; Haberland, K.; Zettler, J.‐T.; Richter, Wolfgang

doi:10.1016/s0022-0248(98)00650-2

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…The occurrence of segregation during growth interruptions was already predicted by theoretical calculations [20]. Furthermore, optical in-situ online observations on similar samples show the dissolution of already existing quantum dots during growth interruptions [21]. In the present work, we confirm these first observations and demonstrate how the segregation and dissolution depends on the particular arrangement of the growth parameters.…”

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confidence: 85%

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Segregation effects during GaAs overgrowth of InAs and InGaAs quantum dots studied by cross‐sectional scanning tunneling microscopy

Eisele

Timm

Lenz

et al. 2003

phys. stat. sol. (c)

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We present a cross-sectional scanning tunneling microscopy study of segregation effects during the overgrowth of InAs and InGaAs quantum dots by GaAs. The thickness of the overgrowth layer and the insertion of a further growth interruption after a thin overgrowth layer are responsible for the occurrence of a vertical segregation of InAs material into this GaAs overgrowth layer. In an extreme case this segregation leads to a complete dissolution of already existing quantum dots.1 Introduction Since a couple of years the growth of quantum-dot heterostructures is of considerable interest in semiconductor physics. Especially self-organized InAs and InGaAs quantum dots within a GaAs matrix are an often investigated system [1]. But the details of the growth process are still not understood completely. An atomically resolved investigation of the spatial structure and local stoichiometry is important to improve the knowledge about the growth process. For optical and electronic studies as well as for applications the quantum dots have to be overgrown. Such overgrown structures are usually characterized by cross-sectional transmission electron microscopy [2]. But with this technique only averaged information over columns of atoms can be achieved. In this work we use cross-sectional scanning tunneling microscopy (XSTM), enabling us to study the atomically resolved structure in more detail at a surface prepared by cleavage perpendicular to the growth direction [3][4][5]. Using this technique, several studies of the spatial parameters of InAs and InGaAs quantum dots were presented recently [6][7][8][9][10][11][12][13][14][15][16][17][18][19].In this work the influence of the growth parameters on segregation effects during the overgrowth of InAs and InGaAs quantum-dot structures by GaAs is studied in detail for samples grown by metalorganic chemical vapor deposition (MOCVD). Comparing the growth parameters we found that especially the insertion and the arrangement of growth interruptions after a thin GaAs overgrowth layer is responsible for the occurrence of segregation and thus for the intermixing of the dot and host materials. The driving force for this segregation is the strain acting at the growth surface until the quantum dot structure is covered by a sufficiently thick GaAs layer. The occurrence of segregation during growth interruptions was already predicted by theoretical calculations [20]. Furthermore, optical in-situ online observations on similar samples show the dissolution of already existing quantum dots during growth interruptions [21]. In the present work, we confirm these first observations and demonstrate how the segregation and dissolution depends on the particular arrangement of the growth parameters.

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confidence: 85%

“…The sample temperature was held at 500 °C during the whole growth process. From optical in-situ online control it is known that quantum dots were present before the overgrowth with GaAs, while the optical signal from the quantum dots decreases during the growth interruption, indicating the dissolution of the already existing dots [21].…”

Section: Methodsmentioning

confidence: 99%

Segregation effects during GaAs overgrowth of InAs and InGaAs quantum dots studied by cross‐sectional scanning tunneling microscopy

Eisele

Timm

Lenz

et al. 2003

phys. stat. sol. (c)

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“…These results are in agreement with the work of (Takehama et al, 2003) who has studied the influence of the GaAs capping layer thickness on quantum dot morphology. The stronger dissolution of bigger dots can be also deduced from reflectance anisotropy results presented in (Steimetz et al, 1998). In conclusion of this section the GaAs capping layer proved to have many disadvantages for a quantum dot laser design.…”

Section: A) B)mentioning

confidence: 64%

“…The capping process of InAs quantum dots can be monitored in situ by time resolved reflectance anisotropy spectroscopy, which enables one to observe in situ the mechanism of In atoms migration from quantum dots and surfactant behaviour of In atoms during GaAs capping layer growth (Steimetz, 1998). To monitor processes during the capping of quantum dots by GaAs layer we grew a set of samples A1, A2 and A3 using Triethyl gallium (TEGa), Trimethyl indium (TMIn) and Tertiary-butyl arsin (TBAs).…”

Section: A) B)mentioning

confidence: 99%

“…The localization of electrons in dots can be further improved by graded composition of InGaAs (Kim, 2003) or by combining the InGaAs strain reducing layer with InAlAs (Kong, 2008). Unfortunately, graded InGaAs composition is difficult to achieve when metal-organic vapour phase epitaxy is used for structure growth due to high In segregation during capping (Steimetz, 1998). Also the combination of InGaAs with InAlAs cannot be used by this technology because of the high decomposition temperature of available Al precursors.…”

Section: Ingaas Strain Reducing Capping Layermentioning

confidence: 99%

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