From Dislocations to Luminescence: Heteroepitaxy of Dissimilar Semiconductors for Infrared Optoelectronics
Integrating dissimilar semiconductors on a single crystalline platform could enable the next generation of devices for optical communication and sensing. Materials such as III-V and chalcogenide semiconductors, when epitaxially integrated with established platforms, offer distinct optoelectronic properties that expand the capabilities of conventional technology. However, bridging structural and chemical mismatches between these crystals introduces extended crystal defects such as dislocations, making this a significant materials science challenge. A key theme of this talk is that structural perfection is not always achievable or even necessary in heteroepitaxy. Materials and device design can instead be used together to mitigate or tolerate the effects of these defects on performance.
In this talk, I will first show how understanding dislocation dynamics led us to design more defect-tolerant III-V telecom lasers on silicon. By combining alloy hardening with InAs quantum dots, we realized lasers 100àmore reliable than prior state-of-the-art devices. I will then contrast this approach with IV-VI semiconductors such as PbSe, which we demonstrate can tolerate naturally high dislocation densities while maintaining efficient infrared light emission at wavelengths spanning 3-8 õm for sensing applications. I will conclude with anisotropic chalcogenides, including SnSe, where we developed heteroepitaxial approaches to preserve optical anisotropy and harness crystalline-to-crystalline phase transitions for reconfigurable photonics. By identifying the key limitations in mismatched epitaxy, we find new ways to preserve function during scalable integration of optoelectronic materials.
Bio: Kunal Mukherjee is an assistant professor in the Department of Materials Science and Engineering at Stanford University. His research focuses on compound semiconductor thin-film synthesis and defect science. He received a B.Eng. in electrical engineering from Nanyang Technological University, an M.S. from the National University of Singapore, and an M.Eng. and Ph.D. in materials science and engineering from MIT. Before joining Stanford, he held postdoctoral appointments at IBM and MIT and served as an assistant professor in the Materials Department at UC Santa Barbara from 2016 to 2020. His work on epitaxy and crystal defects has been recognized with an NSF CAREER Award, the Corbett Prize at the International Conference on Defects in Semiconductors, the Young Scientist Award at the International Symposium on Compound Semiconductors, and the Young Investigator Award at the North American Molecular Beam Epitaxy Conference.