The Microscopic Origin of Efficiency Droop in LEDs
Marco Bernardi, Assistant Professor of Applied Physics and Materials Science, and his colleagues’ semiconductor research has shown that the coupling between electrons and thermal vibrations may be sapping energy from Light-emitting diodes—or LEDs. "Our work shows for the first time that the ever-present interaction between electrons with lattice vibrations can, by itself, explain why excited electrons can leak out of the active layer and account for inefficiencies in GaN LEDs," Professor Bernardi says. [Caltech story]
Professor Bernardi Wins AFOSR Young Investigator Award
Marco Bernardi, Assistant Professor of Applied Physics and Materials Science, has won a 2017 Air Force Office of Scientific Research (AFOSR) Young Investigator Award. The objectives of this program are: to foster creative basic research in science and engineering, enhance early career development of outstanding young investigators, and increase opportunities for the young investigators to recognize the Air Force mission and the related challenges in science and engineering. Professor Bernardi received the award for his proposal entitled, “Ab Initio Electron-Defect and Electron-Phonon Scattering for Understanding and Designing High-Mobility Semiconductors and Oxides.” [AFOSR Press Release]
Studying Entropy in Metallic Glasses
Brent Fultz, Barbara and Stanley R. Rawn, Jr., Professor of Materials Science and Applied Physics, and colleagues have pinpointed that arrangement of atoms is the main source of an increase in entropy during the glass transition. One persistent mystery about metallic glasses occurs at the so-called "glass transition." A cold metallic glass is hard and brittle, but when it is heated past a certain point—the glass transition—it becomes soft. [Caltech story]
Professor Minnich Receives IPPA Junior Prize
Austin Minnich, Professor of Mechanical Engineering and Applied Physics, is a recipient of the International Photothermal and Photoacoustics Association (IPPA) Junior Prize. He received the prize for outstanding contributions to the understanding of quasiballistic thermal transport, including the development of photothermal methods to directly probe heat conduction at length scales comparable to phonon mean free paths; for demonstrating how microscopic transport properties of thermal phonons in solids may be obtained using photothermal experimental methods along with ab-initio calculations; and for advances in the mathematical treatment of quasiballistic transport using the Boltzmann equation.