Title: Direct bandgap group IV materials for photonic devices 

Speaker: Prof. Hung Hsiang Cheng（ Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University ）   

Time: Dec. 1, 2015 14:30PM 

Venue: No.101 Meeting Room, IOS, CAS 

Abstract: As we all know that, the group IV element of Si and Ge are the basic building elements for various electronic devices. Recently, the size of these devices continues to shrink in dimension, pushing to its physical limit. These materials, have been mentioned less for its optical properties. This is simply because the optical efficiency of these materials is poor due to its indirectness energy band. In this talk, a tangiable direct bandgap group IV material is discussed－Sn-based group IV materials. Some of our results on GeSn-based photonic devices and an overall view on the present progress are present. Using these advanced diodes, mid-infrared image is demonstrated. If the group IV photonic is achieved, then the reward could open a new scope for on-chip CMOS optoelectronic systems. It will be applicable for various applications like, sensing, and free-space communications.

Biography：Dr. Cheng received his Ph.D. in Physics from the Oxford University, UK. Dr. Cheng’s research activities center around Si-related topics mainly focusing in three areas: (a) molecular Beam Epitaxy (MBE) growth of IV-IV compounds, (b) developments and Physics of semiconductor nano patterns for opto-electronic, and (c) advanced direct bandgap group IV materials (Sn-based group IV compounds and heterostructures) for optical emitters for telecommunication. He has published more than 100 refereed articles. Several papers have been selected by American Institute of Physics, American Physical Society and Editor’s pick in APL. His group has demonstrated the first group IV direct bandgap light-emitting diode and the highest responsivity mid-infrared photodetectors operated at room temperature. Currently he is working at National Taiwan University. He is a member of several Technical Committees.