| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
AA2, Atomic Structure of InAs/InGaAsP/InP(001) Quantum Dashes and Decomposition of the InGaAsP Matrix Material |
| Author(s) |
Andrea Lenz, Holger Eisele, Florian Genz, Lena Ivanova, Rainer Timm, Dieter Franke, Harald Künzel, Udo Pohl, Mario Dähne |
| On-Site Speaker (Planned) |
Andrea Lenz |
| Abstract Scope |
Semiconductor nanostructures based on InP are interesting for various applications in opto-electronics at datacom emission wavelengths around 1.55 μm. In contrast to InAs deposition on GaAs, self-organized growth of InAs on InGaAsP/InP leads to more elongated structures, referred to as quantum dashes (QDashes). Here we study the structural properties of stacked InAs/InGaAsP QDashes buried in a heterostructure pin-diode, using cross-sectional scanning tunneling microscopy (XSTM). Samples with InAs layers embedded in an In0.78Ga0.22As0.47P0.53 matrix were grown lattice-matched on InP(001) using metal¬organic vapor phase epitaxy. XSTM images scanned at both the (-110) and (110) cleavage surfaces show ~2 nm high InAs QDashes, extending to about 15 nm along the [110] and to about 60 nm along the [ 110] direction. They are characterized by an almost pure binary InAs stoichiometry and cover almost the entire surface with typical center-to-center distances of 20 nm along the [110] direction and of 70 nm along the [-110] direction, corresponding to a QDash density of 7 x 10^10 cm-2. The InGaAsP material between the InAs QDash layers appears inhomogeneous with bright regions separated by darker areas. From similar observations at filled-state and empty-state images we conclude that the quaternary material partly de¬com¬poses into columns of InAs-rich regions, which appear bright, and darker GaP-rich regions. The corresponding stoichiometry variation could be determined by a quantitative analysis of the strain-induced outward relaxation of the cleavage surface, amounting to about +/- 10% for both sublattices or up to +/- 20% if the decomposition occurs only at one sublattice.
Images taken at both orthogonal cleavage planes show evidence for a spatial correlation of the InAs QDashes with the decomposition of the InGaAsP matrix material. Furthermore, a vertical stacking is found for the QDashes in the different InAs layers even being separated by the unusually large distance of 40 nm. It is demonstrated that InAs QDash formation on InGaAsP occurs by nucleation on initially slightly de¬composed InAs-rich regions. This effect is intensified on top of an InAs QDash layer, leading to a column-like modulation of the InGaAsP composition, and hence a preferential vertical alignment of the QDashes in subsequently grown InAs layers. |
| Proceedings Inclusion? |
Undecided |