Date and Time:  7-Nov-2023  2pm 

Speaker:  Li Wang, Senior researcher, RIKEN, Japan

Host: Quanyong Lu ( BAQIS）

Title: Recent development of terahertz quantum cascade lasers based on GaAs or GaN semiconductor material systems

Venue: Room 526

Abstract: 

Despite its wide range of potential applications, terahertz (THz) frequency range (1-10 Thz) is often deemed as an relatively underexplored frequency domain due to the lack of high power THz emitters. Traditional electronic or photonic devices has failed to bridge this spectral gap for various reasons. Quantum cascade lasers (QCLs) based on electron’s intersubband transitions and elaborate semiconductor material epitaxy technology have emerged as one of the most promising laser sources in this spectral range. In my presentation, I will first delve into our latest developments on this type of device, including the efforts to achieve high-temperature operation (>200 K) for GaAs THz-QCLs, and also our endeavors to lasing action from GaN THz-QCLs. The presentation will also encompasses a theoretical understanding of quantum transport utilizing nonequilibrium Green’s function model, the exploration of new laser designs, the high-quality growth of both materials using various epitaxy techniques (MBE/MOCVD), and analysis of device performance.

About the Speaker:

Dr. Wang Li earned his Ph.D in semiconductor physics from Nankai university in Dec. 2013. Since 2014, he has held positions as senior researcher in Japan, first at Toyota technological institute and later at RIKEN. His research primarily focuses on the epitaxial growth of semiconductor materials, including the use of molecular beam/chemical beam epitaxy for GaAs and GaAsN, as well as the metal-organic chemical vapor deposition for GaN. For semiconductor devices, Dr. Wang experiences on silicon-based solar cells previously, and now focus on quantum cascade lasers. Over the past five years, he has led four fundings by the Japan society for the promotion of science (JSPS), and two collaborated projects with Tohoku university. He has successfully applied for and been granted 13 overseas Patents. Dr. Wang is members of both the Japan society of applied physics (JSAP) and the Japan institute of electronics, information, and communication engineers (IEICE). Since 2020, he has served as an invited screening member for the JSPS young researcher projects and innovative projects. He has published over 30 journal papers, such as Applied physics letters and Applied surface science. In recognition of his contributions, he received the Toyota research prize in 2016 and the RIKEN Ohbu prize in 2023.