ECE EDS Seminar: Paul J. Simmonds: Tensile-strained self-assembly: Nanoscale stretching creates novel quantum materials
Location
Description
Cornell Electron Devices Society (EDS) presents:
Paul J. Simmonds
Boise State University
Tensile-strained self-assembly: Nanoscale stretching creates novel quantum materials
Abstract
Since the early 1990s, self-assembled quantum dots (QDs) have been the subject of intensive research for technologies ranging from high-stability lasers, to intermediate band solar cells. Driven by compressive strain, semiconductor QDs form spontaneously on the (001) surfaces of both III-V and group IV materials. However, for certain applications, QDs grown on non-(001) surfaces, or QDs grown under tensile rather than compressive strain are needed. The low fine-structure splitting of (111) QDs should make them ideal entangled light sources. Tensile-strained QDs would have dramatically reduced semiconductor band gaps and a light-hole exciton ground state, with implications for infrared optoelectronics and quantum transduction. However, until recently it has been enormously challenging to synthesize non-(001) or tensile-strained QDs that are free from crystallographic defects.
I will introduce a robust approach to QD self-assembly that overcomes these difficulties, and explain how using molecular beam epitaxy we can reliably and controllably grow defect-free, tensile-strained QDs on (111) and (110) surfaces. I will discuss the application of tensile-strained self-assembly to several different material systems, and present data confirming the promising properties of these novel QDs for entangled photon emission. I will also describe how we can use a similar approach to create highly tensile-strained quantum wells on (111) and (110) surfaces. The light-hole exciton ground state in these quantum wells is of great interest for exploring low-dimensional quantum transport and contributing to the search for Majorana bound states.
In summary, tensile-strained self-assembly represents a powerful tool for heterogeneous materials integration, and the development of novel quantum information platforms.
Bio
Dr. Paul Simmonds completed his Ph.D. in semiconductor physics at the University of Cambridge in 2008, followed by postdoctoral positions at the University of Minnesota, UCSB, and Yale University. While at Yale, Simmonds discovered that by using tensile strain it is possible to create III-V quantum dots on (110) and (111) surfaces, with implications for the fields of quantum information science and spintronics. Starting in 2011, he managed the Integrated NanoMaterials Laboratory at UCLA, and Chaired the IEEE Photonics Society chapter. Dr. Simmonds joined Boise State University in 2014, with joint appointments in Physics and Materials Science, and was promoted to Associate Professor in 2020. He is a Senior Member of the IEEE, winner of the 2018 North American Molecular Beam Epitaxy Young Investigator award, and a National Science Foundation CAREER awardee.