Songrui Zhao, Ph.D.
The Molecular Beam Epitaxy Laboratory
Department of Electrical and Computer Engineering
McGill University, Montreal, Canada
III-Nitride Nanostructures and Their Application to Optoelectronic Devices
Location: BTEC Room 135
Tuesday, January 24th 2017 - 11:00 am
In 2014, the Nobel Prize in Physics was awarded to three researchers for their invention of GaN-based blue light emitting diodes (LEDs), which have revolutionized today's lighting technology. However, equally technologically important deep ultraviolet (UV) and near-infrared (NIR) LEDs and lasers with GaN-based III-nitride materials (GaN, InN, AlN) are rather immature. For example, the turn-on voltage of Ga(Al)N quantum well deep UV LEDs increases drastically as the increase of Al content; and for the end compound AlN, the turn-on voltage is 20-30 V while the bandgap energy of AlN is 6 eV. Moreover, Ga(Al)N quantum well lasers shorter than 336 nm are still hard to achieve. In addition, InN p-i-n NIR LEDs have remained difficult to obtain with epilayers.
Comparing to bulk materials, materials with reduced dimensions can have fundamentally different electrical and optical properties, and thus provide a new avenue to solve material challenges and produce technologically important devices. In this seminar, I will show that using III-nitride nanowire heterostructures grown by molecular beam epitaxy (MBE), quite a few underlying material challenges for III-nitride deep UV and NIR LEDs and lasers, e.g., p-type doping, can be largely addressed, which leads to devices that are not possible to realize previously, such as AlN LEDs with 6 V turn-on voltage, electrical injected AlGaN deep UV lasers at 239 nm, and InN p-i-n NIR LEDs.
Dr. Songrui Zhao holds Ph.D. degrees in Electrical Engineering and Solid State Physics from McGill University (Montreal, Canada) and Zhejiang University (Hangzhou, China), respectively. He is currently a Research Fellow in the Department of Electrical and Computer Engineering at McGill University. In the past few years, he has been working on the MBE growth and characterization of III-nitride nanowire heterostructures and their application to optoelectronic devices, with a recent focus on deep UV LEDs and lasers. His research on electrically pumped deep UV lasers has been highlighted in Laser Focus World, Compound Semiconductor, Semiconductor-today, etc. He is also the recipient/co-recipient of the Outstanding Student Paper Award from the 29th - 31th North American MBE Conference and the 18th International Conference on MBE. He has published more than 50 peer-reviewed journal papers. He is also the author/co-author of 5 book chapters on nitride semiconductors.