Title: Forces that drive the formation of self-assembled nanostructures
Speaker: Dayan Ban, University of Waterloo
Location: Room 616, Physics Building
Time: 14:00-15:00, Tue, July 21, 2015
The operation and performance of active photonic devices are governed by inner workings such as electric potential distribution and dynamic charge carrier distribution, which can conventionally be calculated from theoretical modeling but rarely be measured directly from experiments. The experimental characterization of active photonic devices is mainly focused on input/output behaviors or static structural information. In the former case, the devices are in operation but no nanoscopic information can be obtained. In the latter case, nanoscopic structural information can be obtained by using scanning electron microscopy and transmission electron microscopy but the devices under inspection are not in their working condition. Scanning probe microscopy, including scanning spreading resistance microscopy, scanning capacitance microscopy and scanning voltage microscopy (SVM), is a novel and enabling tool to quantitatively probe internal dopant profile, voltage distribution and carrier distribution at nanometer scales. In this talk, I will present our experimental study by applying scanning probe microscopy to a few representative photonic devices – buried heterostructure (BH) lasers, ridge waveguide lasers, terahertz (THz) quantum cascade lasers (QCL) and interband cascade lasers (ICL). The experimental results demonstrate that the unique SPM technique can reveal the inner workings, thus connect internal mechanism with external measures. The demonstration of resolving dynamic charge carrier density distribution and electric potential profile in an operating optoelectronic laser device is unprecedented and could open the door to many future applications in probing the underlying mechanisms for many puzzling issues such as sub-par performance and degradation in nanoelectronic devices, quantum devices and optoelectronic devices.
Dayan Ban is a Professor of Nanotechnology Engineering in the Department of Electrical and Computer Engineering of the University of Waterloo. He received a B.Sc. and M.A.Sc at the University of Science and Technology of China, Hefei, China. He received a Ph.D. in Electrical and Computer Engineering from the University of Toronto, Toronto, Ontario, Canada, in 2003. During 2001-2002, he was a visiting scientist at Nortel Networks Optical Components, Ottawa, Ontario, Canada. Dr. Ban was on staff at the Institute for Microstructural Sciences of the National Research Council, Ottawa, from Sept. 2002 to Oct. 2005. He was a visiting scientist with the Research Lab of Electronics at MIT in 2009. Dr. Ban is a senior member of IEEE/LEOS and a registered Professional Engineer in Ontario. He has over 15 years experience in designing, fabricating, characterizing optoelectronic devices as well as in scanning probe microscopy technique. Dr. Ban has authored or coauthored over 140 papers in refereed journals and conference proceedings and has contributed a chapter to the seminal book on novel scanning probe microscopy. He holds three patents in novel optoelectronic devices.