OPTICAL CHARACTERISATION OF GROWTH AND INTERDIFFUSION KINETICS IN QUANTUM STRUCTURES

摘要

The growth of low dimensional structures and devices is normally carried out by techniques such as Molecular Beam Epitaxy (MBE) and Metallo-organic Chemical Vapour Deposition (MOCVD). Such techniques, in principle, allow the growth of well defined structures, i.e. known composition and dimensions, and with monolayer sharp heterostructure interfaces. However, for anything but the most favourable combinations of materials the growth mechanisms can become more complicated than the simple growth models might suggest. For example in the MBE growth of III-III-V semiconductor alloys we can be faced with the problem of preferential desorption of one of the group III elements. This can lead to composition and growth rate changes and must be allowed for. A second related problem is surface segregation. Subsequent to growth quantum structures are usually processed to form devices. Often the processing is at elevated temperatures and a worry at this stage is the thermal stability of the structure and in particular diffusion at the interfaces. In this paper we report on the use of optical techniques to characterise such processes.