Microscopic calculations: First principles microscopic atomistic calculations are made of structures and the electronic and optical properties of semiconductor materials and nanostructures using density functional theory. Microscopic calculations of electrical and thermal transport are made using numerical solutions of inelastic Boltzmann equations. Concepts are developed for, and numerical simulations are made of, the coherent responses of nanostructures for quantum information technology. Current interests include graphene, electrical and thermal transport in nanostructures and implementation for quantum information.
Macroscopic modeling: The ESTD has long engaged in substantial and collaborative device modeling activities. These efforts emphasize continuum descriptions, and within this context new approaches have been pioneered for modeling quantum confinement and tunneling, thermoelectroelastic effects in the III-nitrides, and 2D transport in graphene, for example. The device modeling work has impacted a wide variety of experimental programs including Sb-based transistors, GaN and SiC power devices, dual0band infrared photodetectors, solar cells, chemical sensors, graphene transistors, diamond-based cooling, and device failure mechanisms.
Vacuum Electronics: Many approaches are pursued to model the coherent, collective interaction of electromagnetic waves with electron beams for vacuum electronic amplifiers. Particle-in-cell algorithms are developed for high-performance graphic processor units (GPUs) to model interactions in D device geometries. This general-purpose approach supports research of new amplifier concepts, antenna design, and metamaterials. For particular device types, physics-based models are created using tailored approximations to give fast and highly accurate predictions of amplifier performance. To obtain realistic electron beam models for simulation, fundamental calculations of beam formation are made using quantum mechanical electron emission models.
Additional Computational Capabilities are used across the ESTD to support research and development in theory, design and analysis of devices, including electromagnetics, nanoscale plasmonics, and solar cell physics. To complement internally-developed software tools, commercial codes used for research include COMSOL Multiphysics, CST Microwave Studio, Lumerical, HFSS, Analyst, Crosslight, Silvaco and NEXTNANO.