Growth of self-organized quantum dots for optoelectronics applications: nanostructures, nanoepitaxy, defect engineering

We report on the most recent results in novel nanoepitaxy approaches for applications in optoelectronics. The first class of self-organized semiconductor structures is related to spontaneous ordered surface nanofaceting. The most recent data on reflection of high-energy electron diffraction and high-resolution electron microscopy studies prove formation of corrugated superlattices and individual GaAs clusters (quantum dots) on (311)A AlAs surface with characteristic 3.2nm lateral periodicity. Three-dimensional islands may also result in well-ordered surface structures and represent the second class. Recent results indicate that Volmer-Weber and Stranski-Krastanow growth can be realized in the same material system just by tuning the composition of the alloy substrate or cap layer. The other classes are related to two-dimensionally shaped quantum dots (QDs) formed by submonolayer insertions in the InAs-GaAs and other III-V or II-VI systems, to ordered nanostructures formed by spinodal and/or activated spinodal decomposition, for example, in the InGaAs-GaAs and InGaAsN-GaAs materials systems and to arbitrary combinations of different approaches. Uniform in size and in shape QDs may be used in a variety of novel devices. A different class of growth effects is related to dislocations. The elastic interaction of deposited material with dislocations may result in deposit repulsion from the dislocated regions. This effect allows selective elimination of dislocations using in situ annealing. In some cases, dislocation networks may be used for direct fabrication of coherent pedestals having nanoscale sizes for QD fabrication or for use as templates for further nanoepitaxy. We illustrate the application of defect-free self-organized QDs for GaAs-based edge- and surface-emitting lasers operating in the 1.3 mum range. (C) 2003 Elsevier Science B.V. All rights reserved.