Collaborative Research: Atomic Displacement Engineering of Post-epitaxial Thin-films (ADEPT)

非技术描述：现代外延半导体技术的出现导致了光电和电子器件制造的范式转变。具体来说，将半导体层厚度控制在单个原子层内以及在两种不同半导体材料之间创建多个突然界面导致了许多结构的实现，这些结构是现代激光器，探测器和晶体管的关键元素。然而，到目前为止，对异质外延半导体组件中化学成分的精确控制仅限于生长方向-半导体结构进化的下一个飞跃将是实现对所有三个维度成分的精确控制，为量子计算和密码学等新技术的光电构建模块开辟道路。该项目试图通过利用纳米压痕引起的机械力来横向控制现有外延技术产生的半导体异质结构中的化学成分来实现这一目标。该项目将纳米尺度化学成分和结构的实验测量与原子扩散的多尺度计算机建模结合起来。利用计算机模型，该模型部分由专门定制的实验提供信息，该团队探索了一个广泛的参数空间，并确定了有效和可靠地驱动原子扩散所需的必要操作条件。如果成功，这个项目的结果将为创造一种具有广泛应用潜力的新型半导体结构铺平道路。该项目作为一个多学科的家，培训研究生和本科生在两个参与机构。为代表性不足的群体提供本科研究机会是一个特别的重点，新墨西哥大学的学生被招募到宾夕法尼亚大学参加暑期研究机会。技术描述：在这个项目中，研究小组研究了一种在外延生长的III-V半导体系统中横向定义纳米级成分模式的新策略。这种多步骤策略被称为后外延薄膜的原子位移工程，或ADEPT，它与传统的异质外延方法相结合，可能为创建具有高度可控性的三维量子势垒配置提供实用途径。ADEPT方法采用空间图型应力场和热退火来驱动由两种不同大小的可移动原子组成的化合物半导体合金薄膜的扩散和对弹性应力的扩散响应。应力场是通过将可重复使用的、预图案化的纳米柱阵列压在半导体衬底上施加的。值得注意的是，“压印”ADEPT策略不依赖于难以控制的子相成核和生长，适用于存在两种不同尺寸的移动原子的任何材料体系。该团队最近在SiGe中展示了ADEPT方法，并在这里研究了其在III-V异质外延系统中的更广泛应用，即InP支持的InGaAs和GaAsSb。与SiGe相反，这些材料中的原子扩散率并没有完全表征，特别是作为温度和弹性应力的函数，这阻碍了预测建模和充分探索ADEPT过程的能力。该研究活动旨在通过两步计算机辅助实验设计方法克服大工艺参数空间和有限实验吞吐量所带来的障碍。在第一阶段，使用一系列相对“简单”的实验来开发数据辅助模型，这些实验专门为III-V材料相互扩散的参数化模型生成信息。在第二阶段，使用参数化模型来探索多维参数空间，并确定进行ADEPT过程实验演示的合适条件。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Description: The advent of modern epitaxial semiconductor technologies has resulted in a paradigm shift in optoelectronic and electronic device fabrication. Specifically, the control of semiconductor layer thickness to within a single atomic layer and the creation of multiple, abrupt interfaces between two different semiconductor materials have led to the realization of a host of structures that are key elements in modern lasers, detectors and transistors. However, to date, precise control of chemical composition in heteroepitaxial semiconductor assemblies has been limited to the growth direction - the next leap in the evolution of semiconductor structures will be to realize precise control of composition in all three dimensions, opening routes to optoelectronic building blocks for new technologies, such as quantum computing and cryptography. This project seeks to achieve this goal by using mechanical forces induced by nano-indentation to laterally control chemical composition in semiconductor heterostructures created with existing epitaxial technology. The project integrates experimental measurements of chemical composition and structure at the nanoscale with multiscale computer modeling of atomic diffusion. Using computer models that have been partially informed by specifically tailored experiments, the team explores a broad parameter space and identifies the necessary operating conditions needed to efficiency and robustly drive atomic diffusion. If successful, the outcome of this project could pave the roadmap for creating a new class of semiconductor structures with broad potential applications. The project serves as a multidisciplinary home for training graduate and undergraduate students at both participating institutions. Undergraduate research opportunities for underrepresented groups is a special emphasis whereby students identified at the University of New Mexico are recruited into summer research opportunities at the University of Pennsylvania.Technical Description: In this project, the research team investigates a new strategy for laterally defining nanoscale compositional patterns in epitaxially-grown III-V semiconductor systems. This multistep strategy is referred to as Atomic-Displacement Engineering of Post-epitaxial Thin-films, or ADEPT, which, coupled with traditional heteroepitaxial methods, may provide a practical pathway for creating three-dimensional quantum barrier configurations with a high degree of controllability. The ADEPT approach employs spatially patterned stress fields and thermal annealing to drive diffusion in a compound semiconductor alloy film comprised of two mobile atomic species with different sizes and diffusional responses to elastic stress. The stress fields are applied by pressing a reusable, pre-patterned array of nanopillars against the semiconductor substrate. Notably, the "press-and-print" ADEPT strategy does not rely on nucleation and growth of sub-phases that are difficult to control and is applicable to any material system in which two mobile atomic species of different sizes are present. The team has recently demonstrated the ADEPT approach in SiGe and here investigates its broader application to III-V heteroepitaxial systems, namely InGaAs and GaAsSb, both supported on InP. In contrast to SiGe, atomic diffusivities in these materials is not fully characterized, particularly as a function of temperature and elastic stress, preventing predictive modeling and the ability to fully explore the ADEPT process. The research activity seeks to overcome the obstacles posed by a large process parameter space and limited experimental throughput with a two-step, computer-aided experimental design approach. In the first stage, data-assisted models are developed using a sequence of relatively "simple" experiments specifically designed to generate information for parameterizing models for interdiffusion in III-V materials. In the second stage, the parameterized models are used to explore the multidimensional parameter space and identify suitable conditions for performing experimental demonstrations of the ADEPT process.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.