Xiang Yang Liu

Optoelectronic devices, central to many aspects of current and emerging technologies, can be exposed to extreme radiation environments when deployed in specific applications. These environments can induce complex materials effects within the device, resulting in significant device performance degradation. A comprehensive multiphysics tool that can precisely capture the dynamics and reliably predict the behavior of optoelectronic components is needed for interpreting experimental observations and enabling performance optimization without extensive reliance on costly and time-consuming experimental iterations. Capturing all the relevant physics, however, is nontrivial. At the device scale, models require solving a system of nonlinear partial differential equations that govern charge carrier transport, electrostatics, and, in optically active regions, electromagnetic wave dynamics. This study presents a multiphysics simulation approach for such devices using the MOOSE (Multiphysics Object-Oriented Simulation Environment) finite element framework. This framework enables the coupling of semiconductor electronic and optical physics, where the electronic behavior is described by Poisson's equation and the drift-diffusion equations, while the optical response is introduced through photon generation from carrier recombination processes and the propagation of electromagnetic waves. We describe two optoelectronic device structures, a PiN diode and a laser diode, to highlight the coupling of electronic and optical physics within a unified computational model. Ultimately, this work demonstrates how an open-source multiphysics framework can be leveraged to advance the computational study of semiconductor optoelectronic devices, providing a scalable pathway toward modeling more complex systems beyond specific geometries or material platforms under extreme radiation environments.

Radiation-resilient optoelectronic materials are highly desired in space and nuclear applications, and understanding the relevant defects and electronic processes in those materials is crucial for both current and next-generation applications. GaAs is a prototypical semiconductor that serves as a foundational system for describing and understanding optoelectronic devices. In this review, both experimental studies and molecular dynamics (MD) simulations of irradiated GaAs are reviewed, with particular emphasis on the deep-level transient spectroscopy, irradiation-induced amorphization zones, and MD predictions of damage structures. The MD results are also compared to predictions of the non-ionized energy-loss model. Recent theoretical studies, in particular, density functional theory based calculations on the simple intrinsic defects and defect clusters in GaAs, are also reviewed. These defects have an important role in dictating the evolution of GaAs in radiation damage environments, as they impact the coupled dynamics of charge carriers. Finally, possible gaps and challenges toward the general understanding of defect evolution in GaAs are discussed.

The U.S. Department of Energy's Office of Scientific and Technical Information