Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung

Hamburg, Germany

Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung

Hamburg, Germany

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Heyn C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Schnull S.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Jesson D.E.,University of Cardiff | Hansen W.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung
Nanoscale Research Letters | Year: 2014

We describe a method to control the shape of nanoholes in GaAs (001) which combines the technique of local droplet etching using Ga droplets with long-time thermal annealing. The cone-like shape of inverted nanoholes formed by droplet etching is transformed during long-time annealing into widened holes with flat bottoms and reduced depth. This is qualitatively understood using a simplified model of mass transport incorporating surface diffusion and evaporation. The hole diameter can be thermally controlled by varying the annealing time or annealing temperature which provides a method for tuning template morphology for subsequent nanostructure nucleation. We also demonstrate the integration of the combined droplet/thermal etching process with heteroepitaxy by the thermal control of hole depth in AlGaAs layers. © 2014 Heyn et al.; licensee Springer.


PubMed | University of Cardiff and Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung
Type: Journal Article | Journal: Nanoscale research letters | Year: 2014

We describe a method to control the shape of nanoholes in GaAs (001) which combines the technique of local droplet etching using Ga droplets with long-time thermal annealing. The cone-like shape of inverted nanoholes formed by droplet etching is transformed during long-time annealing into widened holes with flat bottoms and reduced depth. This is qualitatively understood using a simplified model of mass transport incorporating surface diffusion and evaporation. The hole diameter can be thermally controlled by varying the annealing time or annealing temperature which provides a method for tuning template morphology for subsequent nanostructure nucleation. We also demonstrate the integration of the combined droplet/thermal etching process with heteroepitaxy by the thermal control of hole depth in AlGaAs layers.


Nemcsics A.,H+ Technology | Nemcsics A.,Research Institute for Technical Physics and Materials Science | Tth L.,Research Institute for Technical Physics and Materials Science | Dobos L.,Research Institute for Technical Physics and Materials Science | And 5 more authors.
Superlattices and Microstructures | Year: 2010

Self-assembled strain-free quantum dot (QD) structures were grown on AlGaAs surface by the droplet epitaxal method. The QDs were developed from pure Ga droplets under As pressure. The QDs were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Both techniques show that the QDs are very uniform in size and their distribution on the surface is also homogeneous. The high resolution cross-sectional TEM investigation shows perfect lattice matching between the QD and the substrate, and also the faceting of the side walls of QD can be identified exactly by lattice planes. Analytical TEM (elemental mapping by EELS) unambiguously identifies the presence of Al in the QD. © 2010 Elsevier Ltd. All rights reserved.


Nemcsics A.,Research Institute for Technical Physics and Materials Science | Nemcsics A.,H+ Technology | Heyn C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Toth L.,Research Institute for Technical Physics and Materials Science | And 3 more authors.
Journal of Crystal Growth | Year: 2011

We investigate strain-free GaAs quantum dots (QDs) fabricated by filling of nanoholes in semiconductor surfaces. The nanoholes are created in a self-organized fashion by local droplet etching with Al droplets as etchants. High resolution transmission electron microscopy (TEM) demonstrates that the quantum dots are free of extended defects. Elemental mapping using local electron energy loss spectroscopy (EELS) shows that the walls surrounding the nanohole openings consist of AlAs. This result confirms that the walls are optically inactive. © 2011 Elsevier B.V. All Rights Reserved.


Nemcsics A.,Research Institute for Technical Physics and Materials Science | Nemcsics A.,H+ Technology | Toth L.,Research Institute for Technical Physics and Materials Science | Dobos L.,Research Institute for Technical Physics and Materials Science | Stemmann A.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung
Microelectronics Reliability | Year: 2011

In this work, droplet epitaxially grown GaAs quantum dots on AlGaAs surface are studied. The quantum dots are investigated in situ with RHEED and ex situ with TEM method. The TEM picture shows that the quantum dot is perfectly crystalline and fits very well to the crystal structure of the substrate. Furthermore, the side of the quantum dot shows stepped facet shape. Here, we show, how the stepped side shape forms from the droplet during crystallization. The RHEED picture shows broadened chevron-tail, which can be explained by the shape of the quantum dot. © 2011 Elsevier Ltd. All rights reserved.


Heyn C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Klingbeil M.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Strelow C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Stemmann A.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | And 2 more authors.
Nanoscale Research Letters | Year: 2010

We study the optical emission of single GaAs quantum dots (QDs). The QDs are fabricated by filling of nanoholes in AlGaAs and AlAs which are generated in a self-assembled fashion by local droplet etching with Al droplets. Using suitable process parameters, we create either uniform QDs in partially filled deep holes or QDs with very broad size distribution in completely filled shallow holes. Micro photoluminescence measurements of single QDs of both types establish sharp excitonic peaks. We measure a fine-structure splitting in the range of 22-40μeV and no dependence on QD size. Furthermore, we find a decrease in exciton-biexciton splitting with increasing QD size. © 2010 The Author(s).


Heyn C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Stemmann A.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Koppen T.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Strelow C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | And 4 more authors.
Nanoscale Research Letters | Year: 2010

Experimental results of the local droplet etching technique for the self-assembled formation of nanoholes and quantum rings on semiconductor surfaces are discussed. Dependent on the sample design and the process parameters, filling of nanoholes in AlGaAs generates strain-free GaAs quantum dots with either broadband optical emission or sharp photoluminescence (PL) lines. Broadband emission is found for samples with completely filled flat holes, which have a very broad depth distribution. On the other hand, partly filling of deep holes yield highly uniform quantum dots with very sharp PL lines. © The Author(s) 2009.


Bartsch T.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Wetzel A.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Sonnenberg D.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Schmidt M.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | And 2 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2013

We study the thermal transport through only few nanometer long GaAs pillars. The pillars are epitaxially embedded between two otherwise isolated thermal reservoirs. Because of the short length and absence of defects and interfaces, the heat current through the pillars is free of distracting influences and perfectly controlled. This enables simple understanding of the observed thermal transport, regarding the pillars as ballistic thermal point contacts. The adjacent figure sketches a side view of the structures employed for the experiments. The thermal conductance of the pillars was measured with the 3ω method. Scheme of the investigated heterostructure with heater and thermal anchor. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Landgraf B.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Slobodskyy T.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Heyn C.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung | Hansen W.,Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2012

The strain relaxation in a metamorphic In xAl 1-xAs buffer placed on top of an AlAs/GaAs superlattice (SL) was analyzed using high-resolution X-ray diffraction and compared to a reference sample containing no SL. Pole figures were constructed to characterize the strain relaxation and twist in the metamorphic buffer layers, AlAs/GaAs SL and GaAs substrate. Lattice mismatch induced strain within such heterostructure causes tilt angles of the layers inside the buffer to rotate around the surface normal. The strong disorder observed in the AlAs/GaAs superlattice supports our previous finding that an AlAs/GaAs SL in the virtual substrate is important for strain relaxation on the substrate side. © 2012 Elsevier B.V..


PubMed | Institute For Angewandte Physik Und Zentrum For Mikrostrukturforschung
Type: Journal Article | Journal: Nanoscale research letters | Year: 2016

We study the optical emission of single GaAs quantum dots (QDs). The QDs are fabricated by filling of nanoholes in AlGaAs and AlAs which are generated in a self-assembled fashion by local droplet etching with Al droplets. Using suitable process parameters, we create either uniform QDs in partially filled deep holes or QDs with very broad size distribution in completely filled shallow holes. Micro photoluminescence measurements of single QDs of both types establish sharp excitonic peaks. We measure a fine-structure splitting in the range of 22-40eV and no dependence on QD size. Furthermore, we find a decrease in exciton-biexciton splitting with increasing QD size.

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