Semiconductor Hetero- and Nanostructures

Abstract: In this thesis, chemical beam epitaxy was used to fabricate nm-sized crystalline structures. Most of the systems were based on heterostructures, i.e., combinations of different kinds of crystalline materials. One-dimensional quantum structures were investigated in two systems, the Stranski-Krastanow grown horizontal GaAs wires on GaP substrates, and the Vapour-Liquid-Solid grown vertical GaAs and InAs nanowhiskers. In addition, the heterostructural interface between GaP and a Si substrate was optimized and investigated. The strain-induced formation of horizontal GaAs quantum wires was studied with atomic force microscope and in situ electron diffraction. The density of the wires could be varied from single, monolithic elongted islands transforming into a corrugated surface. The critical occurrence of anti-phase domain related defects in the growth of heteroepitaxial GaP on Si has been approached. The influence of surface orientation and the selective growth on atomicaly flat sub-µm Si areas have been investigated, resulting in succesful fabrication of defect free GaP nanocrystals. In this system, 200 µm wide pn-junctions containing a heterointerface were fabricated. Semiconductor nanowhiskers have been investigated for InAs and GaAs, with the focus on control of size, position, density and growth rate of the whiskers. Hetereostructures containing InAs and GaAs segments in nanowhiskers have also been pursued.