Computer-aided design of functional materials for optoelectronic application

今天，有限元模拟在工程中经常用于各种设计方案的分析。然而，计算机模拟在探索新材料方面的作用往往限于解释实验观察结果，而不是促进发现具有针对特定应用而量身定做的特性的材料。计算机辅助材料设计方法的成功依赖于理论的能力，即从基本原理出发，将新化合物的原子结构与其性质联系起来，即理想情况下，无需任何先验经验知识。拟议的研究计划旨在促进量子力学方法的发展，以模拟和发明用于广泛光电子应用(激光器、太阳能电池、发光二极管等)的新型功能材料。*在即将到来的资金期间，我们计划专注于开发可用于电信网络的半导体激光器的光学增益材料。新的材料系统有望改善远程光纤网络中光源的热管理和效率。为了实现这一目标，我们将致力于一种完全第一原理的方法来模拟半导体激光材料。重点将集中在化合物半导体合金中不可避免地存在的成分无序的明确描述，以及它在激光增益介质的光学跃迁和损耗特性中的含义。通过将激光增益的量子力学模型与由密度泛函理论计算得到的腔内损耗的细节相结合，将实现可预测的定量理论。这一创新特征使新方法优于以前基于流行的K.P理论的微观模型，后者无法捕捉无序和局域化的影响。量化内在的“无序惩罚”将使我们能够为进一步改进现有技术和评估新兴材料系统的潜力提供一个基准。关于半导体异质结中非辐射损耗的新知识对其他电子器件，如光伏器件和发光二极管具有重要意义。拟议研究的成功可能最终将范式转变为在进行电子设备的制造和表征之前，针对特定应用量身定做的以理论为指导的功能材料选择。

Today finite element simulations are routinely used in engineering for analysis of various design alternatives. However, the role of computer modelling in exploration of novel materials is often limited to interpretation of experimental observations rather than facilitation the discovery of materials with properties tailored to specific applications. The success of a computer-aided material design approach relies on an ability of the theory to relate the atomic structure of novel compounds to their properties from first principles, i.e., ideally without any prior empirical knowledge. The proposed research program aims at advancement of quantum-mechanical approaches to the simulation and invention of novel functional materials for a broad spectrum of optoelectronic applications (lasers, solar cells, light emitting diodes, etc.).******In the upcoming funding period, we plan to focus on the development of optical gain materials that can be used in semiconductor lasers for telecommunication networks. The new material system is expected to improve the heat management and efficiency of the light source in long-range fiber-optic networks. In order to fulfill this goal, we will work towards a fully first-principle approach to the modelling of semiconductor laser materials. The emphasis will be placed on an explicit description of compositional disorder, which is inevitably present in compound semiconductor alloys, and its implication in optical transitions and loss characteristics of the laser gain medium. A predictive quantitative theory will be achieved by combining a quantum-mechanical model of the laser gain with details of intra-cavity losses evaluated from density functional theory calculations. This innovative feature makes the new method superior to previous microscopic models based on popular k.p theory, which are not capable of capturing effects of disorder and localisation. Quantifying the intrinsic "disorder penalty" will allow us to provide a benchmark for further improvement of existing technologies and assess the potential of emerging material systems. The new knowledge obtained about non-radiative losses in semiconductor heterostructures is of fundamental importance to other electronic devices, such as photovoltaic devices and light-emitting diodes. The success of the proposed study can ultimately shift the paradigm towards theory-guided selection of functional materials tailored to specific applications prior to undertaking fabrication and characterisation of electronic devices.