Deposition of epitaxial Ga2O3 and (AlxGa1-x)2O3 thin films by ion beam sputtering: a systematic study

离子束溅射是一种沉积技术，它提供了独特的机会来控制溅射和沉积过程，并研究它们之间的相关性。以前的全面调查的离子束溅射沉积（IBSD）过程中进行了非晶单原子和二元氧化物薄膜。除其他外，它可以表明，该过程提供了一个内在的离子辅助，它可以用来调整几个薄膜的性能。在本提案中，这些研究将扩展到两个目标：（i）复杂的二元和三元薄膜材料的研究，和（ii）IBSD工艺参数和晶体结构和质量的技术相关材料之间的关系的研究。研究的对象将是氧化镓（Ga 2 O3）和氧化铝镓（[AlxGa 1-x] 2 O3）。这些材料由于其有趣的性质而具有高技术兴趣，例如宽带隙和高击穿场强，这使得它们能够用于例如超高功率电子器件中。为了充分利用Ga 2 O3和（AlxGa 1 −x）2 O3薄膜的潜力，需要高结晶质量，这只能通过更好地理解和控制沉积工艺来实现。其他研究小组证明，对于不同的单原子和二元材料，IBSD能够生长具有高结晶质量的外延膜。然而，这些研究忽略了，例如，以前确定的主要工艺参数之一，即溅射几何形状。因此，需要一个全面和广泛的系统研究，以揭示IBSD的全部潜力，关于拟议的目标。本项目旨在全面，系统地研究离子束溅射沉积Ga 2 O3和（AlxGa 1 −x）2 O3薄膜，通过研究工艺参数之间的基本相关性（溅射几何形状、离子种类、离子能量、氧分压、衬底温度、衬底材料）、次级、溅射和散射粒子种类的性质以及薄膜。我们的目标是提高我们的理解如何实现外延和高结晶质量（较大的晶粒，晶格缺陷的密度较低）的薄膜，通过利用离子束溅射的独特功能。中等能量的成膜物种的生长过程中的贡献和它的调整是特别感兴趣的选定的材料系统。

Ion beam sputtering is a deposition technique, which provides unique opportunities to control the sputtering and deposition processes, and to study the correlations between them. Previous comprehensive investigations of the ion beam sputter deposition (IBSD) process were carried out for amorphous monoatomic and binary oxide films. Among others, it could be shown that the process provides an intrinsic ion-assist, which can be used to tune several thin film properties. In the present proposal, these investigations will be extended with two objectives: (i) study of complex binary and ternary film materials, and (ii) study of relations between IBSD process parameters and crystalline structure and quality of technologically relevant material. The subject of the investigation will be gallium oxide (Ga2O3) and aluminum gallium oxide ([AlxGa1−x]2O3). These materials are of high technological interest because of their interesting properties, such as a wide bandgap and a high breakdown field strength, which enable their use, for instance, in ultra-high-power electronics. To fully exploit the potential of Ga2O3 and (AlxGa1−x)2O3 thin films, high crystalline quality is needed, which can be achieved only through a better fundamental understanding and control of the deposition process. Other groups demonstrated for different monoatomic and binary materials that IBSD is capable to grow epitaxial films with high crystalline quality. However, these studies disregarded, for instance, one of the previously identified major process parameters, namely the sputtering geometry. Therefore, a comprehensive and extended systematic study is needed to reveal the full potential of IBSD with regard to the proposed objectives.The present project aims for a comprehensive, systematic study of ion beam sputter deposition of Ga2O3 and (AlxGa1−x)2O3 films by investigating the fundamental correlations between process parameters (sputtering geometry, ion species, ion energy, partial oxygen pressure, substrate temperature, substrate material), properties of secondary, sputtered and scattered particle species, and thin films. The goal is to improve our understanding of how to achieve epitaxy and high crystalline quality (larger grains, a lower density of lattice defects) of the films by utilizing the unique features of ion beam sputtering. The contributions of moderately energetic film-forming species to the growth process and its tuning are of particular interest for the selected material systems.