ELEMENTAL GROWTH PROCESS OF SEMICONDUCTOR ON VICINAL SURFACE

日本东京大学和美国伦敦大学的分子束外延（MBE）生长研究组，通过对MBE生长的研究，可以获得许多有关元素生长过程的信息。K.侧）。日本方面进行了分子束外延实验和理论研究。联合K.方也做了MBE实验和理论工作，特别是集中在蒙特卡罗模拟。这些研究的结果汇集在一起，并进行了讨论，以了解分子束外延的元素生长过程。通过测量二维形核和台阶流动模式之间的临界温度，确定了Ga和Al的表面扩散长度; 2）计算了GaAs分子束外延生长过程中台阶边缘的过饱和度，发现在较高的生长温度下，台阶边缘的过饱和度小于20%。这意味着即使在分子束外延中，也能在台阶边缘建立近平衡。研究了Ga从（111）A到（100）A的扩散，发现生长是由As控制的，这与通常的MBE生长相反，在通常的MBE生长中Ga的材料输运控制生长。4）在刚好低于2D核和阶跃流动模式之间的模式转变的生长温度下，结果表明，与低温生长相比，RHEED强度振荡周期变长。这已经被理解为来自取向差的台阶处的生长在一定程度上贡献了生长。通过对台阶周期变化的详细研究，可以估算台阶反应性随As压强的变化。5）用Monte Carlo方法模拟了台阶上的原子浓度分布，与解析计算结果吻合较好。结果表明，由于各表面上原子迁移率的差异，发生了从（111）A到（100）A的交叉扩散。

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.