Growth mode transitions and scaling behaviour at successive stages of molecular beam epitaxy

Recently developed kinetic model for homoepitaxial growth is extended to th e case of heteroepitaxy (without lattice mismatch) by introducing different adatom surface mobilities in the first layer (heterodiffusion) and in all the next layers (self-diffusion). With this model the effect of two adatom mobilities as a function of the Schwoebel step-edge barrier is studied with an emphasis on the growth mode transitions. It is shown that the differenc e between homo- and heteroepitaxy is concerned to the first few monolayers and is crucially sensitive to the ratio between the hetero- and self-diffus ion coefficients: lower heterodiffusion coefficient with respect to that of self-diffusion improves essentially epitaxial growth and vice-versa. This is important for growing smooth ultrathin layers needed in modern nanotechn ology. Island density kinetics in successive growing layers is studied and it is found that in smooth growth regime it acquires eventually (after depo sition approx. 10 monolayers) a universal scaling form and corresponding sc aling exponents have been determined. (C) 2000 Elsevier Science B.V. All ri ghts reserved.