Formation of heterovalent interfaces: A combined photoemission and ab initio DFT study of GaP/Si heterostructures

在硅上集成III-V半导体是新一代微电子功率器件、高效多结太阳能电池和用于可再生氢发电的光解串联吸收器的理想选择。GaP/Si（001）是伪晶虚拟衬底的理想候选材料，是高效光电器件结构的通用元件。我们的目标是克服目前与极性-非极性异质外延相关的限制挑战，在进一步的III-V集成之前，以生长低缺陷的活性材料。因此，尖锐的GaP/Si（001）界面的制备是金属有机化学气相沉积（MOCVD）的关键技术步骤，因为它强烈影响随后生长的外延膜的质量和最终器件的性能。初步研究表明，v族元素砷的加入对界面结构的调整起决定性作用。目前，界面形成机制在原子尺度上还没有得到很好的理解，这些埋藏界面的电子结构也尚未得到解决。近年来，在减少埋藏的GaP/Si（001）异质界面缺陷形成方面取得了很大进展。因此，该界面不仅是光电应用的通用元件，而且是模型结构，是实现界面电子结构对比实验和从头算研究的关键。在这个双边项目中，我们将加入我们在工业可扩展，最先进的MOCVD外延生长，先进的界面分析和从头算理论方面的互补专业知识，为全面的异质界面研究提供所有必要的元素。因此，我们的目标是解决极性对非极性异质外延中一个历史性的开放问题：如何在补偿界面电荷的同时，尽可能地形成尖锐的界面，以便在界面上获得良好定义的电子特性？我们将采用一种独特的方法，结合制备，光学原位光谱，实验室以及基于同步加速器的光电子能谱技术，深度剖面和从头算密度泛函理论计算，以建立对GaP/Si（001）和GaP/Si(001): as异质界面的结构和电子性质的结论性原子尺度理解。界面的结构将以自下而上，自上而下和原位方法进行研究。我们将介绍原子结构的专门修改，以了解如何调整异质界面的电子特性以及如何在原位控制。该项目的目标是在原子尺度上获得对III-V/IV异质界面形成的基本理解，并直接影响高性能器件的应用。

Integration of III-V semiconductors on silicon is desirable for a new generation of microelectronic power devices, high-efficiency multi-junction solar cells and photolytic tandem absorbers for the renewable generation of hydrogen. GaP/Si(001) is the ideal candidate for a pseudomorphic virtual substrate, a generic element for high-efficiency optoelectronic device structures. The goal is to overcome the today limiting challenges, which are related to polar-on-nonpolar heteroepitaxy, prior further III-V integration in order to grow low-defect active material. The preparation of sharp GaP/Si(001) interfaces thereby is the critical technological step in metalorganic chemical vapor deposition (MOCVD), because it strongly impacts the quality of subsequently grown epitaxial films and the final device performance. Preliminary work showed that the additional group-V element arsenic plays a decisive role for tuning the interfacial structure. Today, interface formation mechanisms are not well understood at the atomic scale and the electronic structure of these buried interfaces has not yet been resolved. Recently, there has been much progress to reduce defect formation considerably at buried GaP/Si(001) heterointerfaces. Therefore, this interface is not only significant as generic element for optoelectronic application, but also as model structure, which is the key to enable comparative experimental and ab initio studies of the interface electronic structure. In this bilateral project, we will join our complementary expertise in industrially scalable, state-of-the-art epitaxial growth by MOCVD, in advanced interface analysis and in ab initio theory to provide all essential elements for a comprehensive heterointerface study. Thereby, we aim to resolve a historic open question in polar-on-nonpolar heteroepitaxy: How can interfaces form as sharp as possible, while compensating interface charges in order to get well-defined electronic properties across the interface? We will apply a unique methodology combining preparation, optical in situ spectroscopy, lab-based as well as synchrotron-based photoelectron spectroscopy techniques, depth profiling and ab initio density functional theory calculations in order to establish a conclusive atomic-scale understanding of the structural and electronic properties of GaP/Si(001) and GaP/Si(001):As heterointerfaces. The structure of the interface will be studied both with bottom-up, top-down and in situ approaches. We will introduce dedicated modifications of the atomic structure in order to understand how the electronic properties of the heterointerface can be tuned and how this can be controlled in situ. The objective of this project is to gain a fundamental understanding of III-V/IV heterointerface formation on the atomic scale with direct implications for high-performance device applications.