ELEMENTAL GROWTH PROCESS OF SEMICONDUCTOR ON VICINAL SURFACE

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Many informations on elemental growth process can be obtained by studying growth of molecular beam epitaxy (MBE) on by the groups of Tokyo University (Japanese side) and London University (U. K. side). The Japanese side made MBE experiments and theoretical studies. The U. K. side did also MBE experiments and theoretical works especially concentrating on Monte Carlo Simulation. The results of these studies were brought together and discussions were made to understand the elemental growth process of MBE. The conclusions so far obtained are summarized as follows.1) By measuring the critical temperature between 2D-nucleation and step flow modes, the surface diffusion lengths of Ga and Al were determined.2) The degree of supersaturation at the step edge during the MBE growth of GaAs was evaluated and it was concluded that it takes a value less than 20% at a relatively high growth temperature. This means the near-equilibrium is established at step edge even in MBE.3) By using micro-probe RHEED MBE. diffusion of Ga from (111)A to (100) was studied and it was found that the growth is carried out by As controlled made in contrast to usual MBE growth where the material transport of Ga controls the growth.4) At the growth temperature just below the mode transition between 2D nuclei and step flow modes, it was found that the period of RHEED intensity oscillation becomes longer compared with that for the growth at lower temperature. This has been understood as the growth at the steps from the misorientation contributes the growth in some part. By a derailed investigation of this period change, one can evaluate the reactivity of the step as a function of As pressure.5) Monte Carlo simulation was made to find the ad-atom concentration profile on the terrace between steps, which agrees very well with the analytical calculation. It is shown that the cross diffusion from (111)A to (100) occurs due to the difference of ad-atom mobility on each surface.