Lateral and vertical ordering in multilayered self-organized InGaAs quantum dots studied by high resolution x-ray diffraction

Abstract

Lateral and vertical ordering in multilayered selforganized InGaAs quantum dots studied by high resolution x-ray diffraction Darhuber Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Darhuber, A. A., Holy, V., Stangl, J., Bauer, G., Krost, A., Heinrichsdorff, F., ... Werner, P. (1997). Lateral and vertical ordering in multilayered self-organized InGaAs quantum dots studied by high resolution x-ray diffraction. Applied Physics Letters, 70(8),[955][956][957]

Optical anisotropy in vertically coupled quantum dots

“…In the In 0.5 Ga 0.5 As samples under investigation, HREM indicates that the QD's have a pyramidal shape, 7,21 and plan-view TEM reveals bases with facets in the ͓100͔ and ͓010͔ directions, and elongated slightly in ͓1-10͔ direction. During the growth of the VCQD samples, the QD's in the initial layer elongate slightly along ͓1-10͔ direction.…”

“…Recently, multiple stacked layers of QD's with GaAs or Al x Ga 1Ϫx As spacers were reported, which show self alignment of the QD's into vertical columns. [4][5][6][7] During the stacking process, the shape uniformity of the dots in the higher layers is improved and thereby the inhomogeneity of the optical transitions is decreased. These vertically coupled quantum dots ͑VCQD's͒ have been characterized by scanning tunneling microscopy, high-resolution x-ray diffraction and transmission electron microscopy ͑TEM͒.…”

“…These vertically coupled quantum dots ͑VCQD's͒ have been characterized by scanning tunneling microscopy, high-resolution x-ray diffraction and transmission electron microscopy ͑TEM͒. 7,8 The vertical alignment is caused by the strain fields of the lower QD layer extending into the barrier material. Due to the strong vertical coupling between the dots, the electronic states can acquire a wire-like character.…”

X-ray diffraction investigation of a three-dimensional Si/SiGe quantum dot crystal

“…[11][12][13][14][15] However, despite the fact that elastic interactions favor lateral ordering of islands as well, they turned out to be rather weak 16 and only rather short-range ordering was observed in the above mentioned systems by atomic force microscopy, transmission electron microscopy, and x-ray diffraction ͑XRD͒. [16][17][18][19][20][21] Apart from vertical island ordering in columnar form, in III-V, 22,23 II-VI, [24][25][26] and IV-VI compounds 27 also oblique ordering was observed, 28 typically for larger spacer layer thicknesses, before for sufficiently wide spacers the ordering finally vanishes. 29 For the PbSe/PbEuTe system the formation of a three-dimensionally ͑3D͒ ordered trigonal island crystal in PbSe island multilayers separated by PbEuTe spacer layers was observed for a certain range of the spacer layer thickness for growth along an elastically soft ͓111͔ direction.…”

Mechanism of organization of three-dimensional islands in SiGe/Si multilayers

“…Lateral and vertical ordering of 3D islands in multilayers has been studied in both the SiGe/Si 2-4 and the InAs/GaAs 5,6 systems and was probably present even in some of the first superlattices grown by molecular beam epitaxy ͑MBE͒. 7 For the SiGe/Si͑100͒ system, it has been shown by atomic force microscopy ͑AFM͒ that coherent 3D islands undergo a transition from a broad size distribution in a single SiGe layer to intraplanar size equalization in a SiGe/Si multilayer structure.…”