Investigation of the Mechanism of Ge/Si heteroepitaxial Growth with Interfacial Reactions

近年来，Ge/Si超晶格在光学器件中的应用受到了广泛的关注，因为Ge/Si多层结构具有直接的带隙。为了制备这些Ge/Si异质结构，有必要深入了解异质外延生长和生长界面固相反应的机理。本文采用原位反射高能电子衍射（RHEED）观察方法，研究了GeH4气源分子豆外延在（100）Si和（811）Si衬底表面上生长Ge初期的生长过程。本文重点研究了异质外延生长的机理以及生长界面上的界面反应。明确了薄膜的生长过程和动态行为。在300-700℃的衬底温度下，薄膜以平行取向的外延关系形成，并逐渐生长出更多的平面。在（100）Si表面上的岛生长阶段，生长岛的主要面最初是（811）Ge面，随着生长最终转变为1311)Ge面。在（811）Si表面的岛状生长中，生长出了具有（811）面的板状Ge岛，但随着生长的进一步，主要的面变成了1311)Ge和（100）Ge面。这些生长过程与Ge薄膜在（100）Si表面的生长过程一致。结果表明，（8111）晶面的Ge岛在（811）Si表面和（100）Si表面上的岛生长初期能量稳定。在生长的初始阶段，由于生长界面附近的固相反应，形成了有序的Ge和Si原子结构。在未来，我们将研究{811}表面的热稳定性，并在界面反应的Ge/Si异质结构体系中明确异质外延生长的机理和有序结构的起源。少

Recently, the application of Ge/Si superlattices to optical devices has received considerable attention, because the Ge/Si multilayer structure has a direct band-gap. In order to fabricate these Ge/Si heterostructures, it is essential to have a thorough understanding of the mechanism of the heteroepitaxial growth and solid phase reactions at growing interfaces. In the present work, the growth process in the initial stage of growth of Ge on (100)Si and (811)Si substrate surfaces by gas source molecular bean epitaxy using GeH4 has been studied by in-situ reflection high energy electron diffraction (RHEED) observation. Focus in this work has been placed on the mechanism of the heteroepitaxial growth with the interfacial reactions at the growing interfaces. The following growth process and dynamic behavior of the film growth have been made clear.A strained film by the monolayer overgrowth mode is formed initially with an epitaxial relationship of the parallel orientation, and Ge islands wi … More th facets are grown with proceeding the growth over examined substrate temperatures of 300-700ﾟC. In the island growth stage on (100)Si surfaces, the predominant facet of the growing islands is (811)Ge planes initially and this changes to 1311)Ge eventually with growth. In the case of the island growth on (811)Si surfaces, plate-shaped Ge islands with (811) facets are grown, but the predomi nant facet changes to 1311)Ge and (100)GE planes with the further growth. These growth processes accord with those of Ge films on (100)Si surfaces. It is concluded that Ge islands with (8111 facets are energetically stable in the initial stage of the island growth on the (811)Si surfaces as well as the (100)Si surfaces.It has been found that an ordered structure of Ge and Si atoms are formed in the initial steps of growth, which results from the solid phase reaction near the growing interfaces. In future, we intend to investigate the thermal stability of the {811} surface and make clear the mechanism of heteroepitaxial growth and the origin of the ordered structure in the system of the Ge/Si heterostructure with the interfacial reaction. Less