Title: Characterization and control of GaN and AlGaN surfaces for high-performance GaN-based transistors
Speaker: Prof. Tamotsu Hashizume(Hokkaido University，Japan)
Time: 10:00(AM),Nov 6,2009
Venue: Academic Meeting Room, Institute of Semiconductors, CAS
Abstract：Highly stable and reliable operation is absolutely required for GaN-based high-efficiency power switching devices and high-power RF AlGaN/GaN HEMTs. For the improvement of operation stability in such devices, in this paper, the surface control technologies will be addressed by introducing an ultrathin-Al-layer process, an atomic layer deposition of Al oxide and a multi-mesa-channel structure with relevant technologies. The “air-gap” CV and the surface conduction measurements revealed that high-density surface electronic states can induce potential instability or local charges at “free” AlGaN surfaces. Based on this characterization, we have developed surface control processes associating with atomic disorder, vacancy defects and oxygen impurity. The atomic layer deposition of Al oxide was employed to control AlGaN surfaces, in combination with the post-annealing using a mixture of nitrogen and oxygen. From the point of view of device design, a multi-mesa gate control structure has been applied to AlGaN/GaN HEMTs. With forming a periodic trench just under the gate region, the multi-mesa gate structure has a surrounding field effect on the 2DEG layer. This resulted in the shallower threshold voltage, higher current drivability and higher current stability.
About Speaker：
Prof. Tamotsu Hashizume received Ph.D degree in electrical engineering from Hokkaido University, Hokkaido, Japan, in 1991. In 1994, he joined the Graduate School of Electronics and Information Engineering, Hokkaido University, as Associate Professor. Since 2004, he has been a Professor of Research Center for Integrated Quantum Electronics, Hokkaido University. His research interests included surface passivation and device processing technologies for III-V compound semiconductors. Currently, his major activity expanded into characterization and control of surfaces and interfaces of GaN and related materials, and their application to GaN-based electron devices. He has authored or co-authored over 150 papers in scientific and technical journals. Prof. Hashizume acts as an area chair (Area 6) in the International Conference on Solid State Devices and Materials (SSDM) and a chair of Electron Devices Committee in the Institute of Electronics, Information and Communication Engineers, Japan (IEICE).