APPROACHES TO UNDERSTANDING MBE GROWTH PHENOMENA

A physical picture of molecular beam epitaxy (MBE) growth is presented in a consistent form taking into consideration the atomistic nature o f crystallization phenomena occurring in this process. To this end, th e entire MBE growth system directly involved in epitaxial crystallizat ion is divided into three different parts. The crystalline solid phase of the substrate, or the already grown epilayer, is one extreme, the gaseous phase of the intersecting molecular beams is the second extrem e and the transition layer in between, where transition from a gas to a crystal occurs, creates the third part of the system. The transition layer, where all processes leading to epitaxy occur, is obviously the most important part of the growth system. Its geometrical form and th e processes occurring there depend strongly on the growth conditions c hosen. The following approaches have been considered when discussing t he attributes of MBE growth processes: (i) thermodynamics, (ii) ''surf ace sites-particle'' interaction analysis, and (iii) chemical bond qua ntum mechanics. Taking as examples: (i) MBE of non-stoichiometric stru ctures, (ii) UHV atomic layer epitaxy, and (iii) self-organization eff ects in MBE, the importance of the transition layer concept for unders tanding MBE growth processes has been illustrated.