Control of the MBE equipment for growth of nano structures
The technique of molecular-beam-epitaxy (MBE) is the most refined for making semiconductor nanostructures. Nowadays, the growth of self-organised nano structures has been intensively investigated. This technique makes it possible the necessary special sample preparation and the in-situ observation of the nanostructures, growing in a self-organising manner. For the sample preparation and its investigation, we need very accurate control of the MBE equipment. In this paper, we present the programable logical controller (PLC) system wich steer our equipment. Here, we show the control of the heating out system of the vacuum chambers, the control of the furnace of the molecular sources and the control of the moving of the shutters.
The RHEED tracking of the droplet epitaxial grown quantum dot and ring structures
Abstract Self-assembled strain-free GaAs quantum dot and quantum ring structures grown by droplet epitaxy were investigated by the RHEED technique. The temporal evolution of these nanometer-scale objects were tracked in situ manner during the growth process. The initial stage of the surfaces was the same for both kinds of quantum objects. We have compared step by step the RHEED pattern in [ 1 1 ¯ 0 ] direction in the case of both quantum objects. After the Ga deposition the pattern becomes diffuse. Almost at the same time with the offering of arsenic the RHEED pattern changed from diffuse to spotty and later changed slowly to spots with chevrons in case of the quantum dot. In case of the quantum ring the situation is quite different. The pattern, which consists of streaks and spots, evaluate slowly and continuously. The different patterns and their different temporal evaluations can be explained with the shape and the kinetic of development of different quantum objects.
Initial growth stage and optical properties of a three‐dimensional InAs structure on GaAs
A few mololayers of InAs is heteroepitaxially grown on GaAs substrate by molecular‐beam epitaxy. Structure and optical properties are investigated. Reflection high‐energy electron‐diffraction observation reveals that an InAs layer forms a three‐dimensional structure with specific facets after two‐dimensional growth. The transmission electron microscope observation shows that these structures have structural anisotropy in the growth plane. Photoluminescense spectroscopy shows that the luminescence from the InAs structures exhibits the polarization property caused by the quantum dot effect of the structural anisotropy.