The range of materials and device systems investigated by our faculty can be roughly separated into III-Nitrides, other semiconductors, organics, and 2D systems.
III-Nitrides
In the III-Nitride area, research is focusing on epitaxy, crystal growh, power electronics, light-emission, lasers, and point-defects. Organic materials are being investigated in the form of polymers as well as small-molecule assemblies, towards applications as organic semiconductors, photovoltaics, electro-optic modulation, or nonlinear optical all-optical switching or frequency conversion. Inorganic semiconductors are of interest for general compound semiconductor technologies, high-speed and power transistors, THz sources for sensing/spectroscopy. Layered and 2D systems are studied theoretically with ab-initio prediction of relevant functionalties, and fabricated using atomic layer deposition (ALD).
Crystal Growth of Ultra-Wide Band Gap Semiconductors
Siddha Pimputkar‘s lab is building foundational capabilities to synthesize and develop ultra-wide bandgap semiconductors, with the aim of leveraging these new materials for superior optoelectronic and electronic devices in fields such as power electronics, high-frequency modulation, or short wavelength emission. These are all important areas towards efficient electric power conversion, or for such health-related applications like the ability of creating powerful ultraviolet emitters for the disinfection of water and surfaces.
The group develops and implements novel equipment and technologies to access new synthesis capabilities for both bulk and thin film growth. Single crystal growth of nitrides is obtained using a variety of techniques. Thin films are grown using traditional and a novel high pressure MOCVD system. Additional work focus on solving the current lack of a scalable industrial technology to grow cubic Boron Nitride: two fundamentally different approaches to its synthesis are being implemented for the first time. In particular, the ammonothermal method and a newly developed flux-based approach carry great promise to deliver inexpensive, large volume single crystals for use in device development.
Other Semiconductors and Thin Film Growth
Sushil Kumar’s lab works on the creation of multiple quantum well systems to be used in quantum cascade lasers for THz emission, as well as on plasmonic structures that can be used for beam shaping.
Nick Strandwitz and his research group are working on Atomic layer deposition, molecular layer deposition, and growth of metal oxides and nitrides, developing new science and technology for thin film growth and processing.
Organics
The very same reason that organic materials allow the multitude of living organisms that we can observe on planet Earth, also leads to enormous flexibility in the design and synthesis of new functionalities based on organic molecules. Organic materials also allow to create large area systems that are flexible and cheap, and that can contribute unique solutions in electronics, optoelectronics, or biomedical devices. One explosive success of organic electronics and optoelectronics of the last 20 years is the development and commercialization of the Organic Light Emitting Diodes (OLEDs, produced by physical vapor deposition of specially designed organic molecules) that power most of the screens of our phones, and also other, larger screens. Within CPN, research on organic molecules focuses on polymers, small molecule assemblies, and semiconductor-organic-hybrid systems.
Polymers/hybrid semiconductors and organics for energy conversion and storage
Elsa Reichmanis‘ lab investigates the chemistry and properties of polymeric and nanostructured materials for advanced optoelectronics via the design and development of organic or organic/hybrid semiconductors systems for flexible and stretchable electronics (such as transistors), and the control of polymer/hybrid semiconductor organization at the molecular through meso-scales. Related research focuses on active materials for lithium-ion electrodes that can have up to 10 times the charge capacity of the graphite electrodes used in current systems, like high-capacity magnetite and silicon anodes, while also exploring flexible electrodes and polymer electrolytes.
Organic small-molecule assemblies
Ivan Biaggio‘s lab is working on ways to integrate active photonics functionality in the nano-scale structures of integrated optical circuits such as those of the silicon-photonics platform. This research focuses on the development and use of small organic molecules that still have a strong ability to interact with electromagnetic waves but that can also be sublimated in high vacuum to build small-molecule assemblies via thermal vapor deposition, a flexible technology that is already used on a very large scale to create organic light-emitting (OLED) displays. The appeal of such small molecules derives from this ability of them forming molecular glasses with low low absorption and scattering losses that can homogenousy fill gaps smaller than 100 nm in photonics circuits, and do so systematically and reproducibly. The structures that one can build in this way will then be used to deliver a desired photonics functionality, such as all-optical switching or ultra high-speed electro-optic modulation.
Semiconductor and Photonic Devices
Sushil Kumar’s lab is working on the design, fabrication, and characterization of semiconductor lasers, in particular distributed-feedback lasers and surface-emitting lasers as applied to Terahertz photonics, sensing and spectroscopy. A focus on the research is on THz and mid-infrared plasmonics, which can be used to obtain large brightness and collimated beams from THz emitters, with the recent demonstration of a multi-watt output in a single spectral mode.
Ning Li’s Semiconductor Emerging Electronic Device (SEED) lab is investigating various emerging semiconductor and photonic devices, including non-volatile memory and logic devices for the next generation computing and semiconductor technologies, optoelectronic devices for optical interconnects and high-speed optical links, and flexible electronics using inorganic and organic semiconductors.