DMREF: GOALI: Tetrahedral Ferroelectrics

Nontechnical Description:Ferroelectricity is the ability to reverse a spontaneous electrical polarization by the application of an external electric field. This property is crucial to many modern electronic and optical technologies, but there has been limited success directly integrating ferroelectric materials with electronics based on conventional semiconductors despite decades of efforts. Part of the challenge is that traditional ferroelectrics exhibit very different crystal structures, bonding, and defect densities from commercial semiconductors such as silicon. This project seeks to resolve this problem by introducing a new class of ferroelectric materials with a tetrahedral bonding structure common to commercial semiconductors. Introducing a new function to tetrahedral semiconductors will represent a step change in the capabilities of integrated electronic and optical devices. This project will discover and develop new tetrahedral ferroelectrics and result in a new mechanistic understanding of ferroelectricity. The project will emphasize workforce development, through the education of students and post-docs trained to accelerate materials discovery via modern approaches to integrated computation and experiment. Technological advances will be accelerated through close collaboration with an industrial partner, Broadcom, Inc. Technical Description:Tetrahedral ferroelectrics such as modified aluminum nitride (AlN) offer a unique opportunity to extend our fundamental understanding of polarization reorientation and to discover new families of materials with enabling non-linear dielectric properties. The recent discovery of tetrahedral ferroelectrics has highlighted gaps in the scientific understanding of ferroelectricity and of polar semiconductors. The current project addresses three sets of fundamental questions: (1) How is switchable polarization related to coercive field, a paraelectric transition and/or stiffness? How is coercive field related to structure? (2) What is (are) the switching mechanism(s) in tetrahedral ferroelectrics? (3) How do local structure, individual and clustered point defects, and synthesis affect switching and breakdown? These questions will be addressed via integrated computation and experimentation, expanding the understanding of the fundamentals of ferroelectricity and of polar semiconductors alike. Enabling ferroelectricity in tetrahedral semiconductors represents a potential step change in semiconductor device capability and offers an attractive alternative to fighting defect accommodation in complex oxides. This project will expand ferroelectric and semiconductor physics, through a greater understanding of the mechanisms of polarization reorientation that welcomes a family of heretofore unknown tetrahedra-based systems to the universe of known ferroelectrics while simultaneously introducing a new intrinsic capability to the toolbox of tetrahedral semiconductors.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.