半导体超晶格二维电子气材料的辐照效应研究

In weapon and space-based applications, two dimensional electron gas materials based on semiconductor superlattice are exposed in fluxes of neutrons and gamma rays, which result in defect generation and aggregation, and ultimately deteriorate the electric properties. It is thus of critical importance to enhance the electrical properties and radiation tolerance of electronic materials to ensure the electronic systems functioning properly under radiation environment. In this study, the role of charge transfer in radiation process will be considered and ab initio molecular dynamics method will be employed to study the radiation effects of Si-Ge, GaAs-AlGaA and GaAs-AlAs. The micro-mechanism for radiation damage will be revealed with ab initio accuracy, and the influences of radiation defects on the carrier concentration and mobility will be predicted, aiming at building models predicative of semiconductor superlattice with superior electric properties and radiation resistance. Based on theoretical predictions, experimental studies will be carried out to investigate the response of Si-Ge, GaAs-AlGaA and GaAs-AlAs to neutron and γ irradiaiton, in order to obtain the relationship between defect distribution and electric performance. The synergetic theoretical and experimental studies will help to modify and improve the theoretical models, and to characterize the electric properties and radiation resistance appropriately. The research results will benefit for improving the electric properties and radiation tolerance of electronic materials and for designing novel materials sustainable and durable for harsh environment applications. The proposed work is not only of great scientific importance, but also has great impacts on engineering application.

半导体超晶格二维电子气材料在武器及航天航空等领域中应用时会暴露在中子、γ等强辐射环境中，导致大量缺陷产生和聚集而使得材料的电学性能退化。如何增强其电学和抗辐照性能，对确保电子器件在辐射环境中正常有效地工作至关重要。本项目拟考虑电荷转移在辐照过程中的作用，采用从头算分子动力学方法模拟Si-Ge, GaAs-AlGaAs和GaAs-AlAs的辐射效应，以第一性原理的精度揭示辐射损伤机制，预测辐照缺陷对载流子浓度和迁移率的影响，提出半导体超晶格材料高载流子迁移率和耐强辐射的理论模型。根据理论预测结果，通过实验研究这些材料在中子和γ辐照下的缺陷分布与电学性能的内在联系，修正和完善理论模型，并结合理论模拟和实验研究结果提出表征材料电学和抗辐照性能的方法。其研究结果将有利于提高电子材料的电学和抗辐照性能，可为新型电子材料的研发提供理论和实验支撑，具有重要的学术研究价值和工程应用参考价值。

半导体超晶格二维电子气材料已广泛应用于航空航天、高能物理及核相关领域的高科技应用。在辐照环境下缺陷的产生、聚集和积累可能会使材料电学性能退化甚至导致器件永久失效。如何增强其电学和抗辐照性能，对确保电子器件在辐射环境中正常有效地工作是十分关键的。在本基金资助下，本项目主要研究半导体超晶格二维电子气材料的辐照效应。主要取得的研究成果如下：（1）通过研究Si/Ge、GaAs/AlAs和GaAs/AlGaAs半导体超晶格材料在辐照前后微观结构和电学性质的变化，我们发现半导体材料成分及堆垛层数、取代元素的浓度、产生缺陷的类型等都会影响二维电子气形成及载流子浓度和迁移率。另外，通过研究不同堆垛层数的半导体超晶格材料的能带结构、电子有效质量浓度和迁移率、不同元素的位移阈能、产生缺陷的类型数量和形成能、损伤态电子有效质量浓度和迁移率，可以评估材料的电学和耐辐照性能。（2）通过研究三种半导体超晶格材料在辐照前后缺陷的类型、浓度和分布，我们发现在大部分情况下，辐照产生的空位、间隙、反位、弗伦克尔对等缺陷会导致电学性能下降，但GaAs/AlGaAs超晶格中各种类型反位缺陷反而提升电子迁移率。研究结果揭示了辐照损伤过程的物理机制，获得了半导体超晶格材料耐辐照性能的规律，对工程应有具有重要的价值。