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极大的关注，因为Ge/Si多层结构具有直接带隙。为了制备这些Ge/Si异质结，有必要对异质外延生长和生长界面上的固相反应机理有一个透彻的了解。用原位反射高能电子衍射(RHEED)研究了Ge在(100)Si和(811)Si衬底上用GeH4气源分子束外延生长初期的生长过程。这项工作的重点是异质外延生长的机制以及生长界面上的界面反应。明确了薄膜的生长过程和生长动力学行为，初步形成了单层过生长模式的应变薄膜，具有平行取向的外延关系，Ge岛为…在所考察的衬底温度300-700ﾟC以上继续生长，生长出更多的面。在(100)Si表面的岛生长阶段，生长的岛的主要面最初是(811)Ge面，随着生长，这最终转变为1311)Ge面。在(811)Si表面岛状生长的情况下，生长出具有(811)晶面的片状Ge岛，但随着进一步的生长，主晶面转变为(1311)Ge和(100)Ge面。这些生长过程与在(100)Si表面上生长Ge膜的过程一致。结果表明，在(811)Si和(100)Si表面上，具有(8111)面的Ge岛在生长初期是能量稳定的，在生长初期形成了Ge和Si原子的有序结构，这是生长界面附近固相反应的结果。今后，我们将进一步研究Ge/Si异质结界面反应体系中{811}表面的热稳定性，弄清异质外延生长的机制和有序结构的来源。较少

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