MSE Seminar: Hiroshi Amano (Nagoya)

Description

Acceleration of Social Implementation of Wide Bandgap and Ultrawide Bandgap Semiconductors

I would like to emphasize the need for the research and development of wide- bandgap (WBG) and ultrawide-bandgap (UWBG) semiconductors, especially GaN, AlN, and their alloys. The contribution of GaN and related materials in LED lighting to energy savings is significant. The application of these material systems is not limited to lighting: replacing Si-based power devices with GaN-based power devices can reduce the total electricity consumption by 25%. GaN-based high-voltage power devices should become the key devices in establishing renewable-energy-based electricity grids because of their high-efficiency, high-speed switching, and high-voltage capability. GaN-based high- frequency and high-power transistors will provide a unique solution for realizing millimeter-wave communication systems.

For the early social implementation of these devices, it is necessary to establish mass production technology. Si-based logic, memory, and power device manufacturing are now mature, and mass production is already widespread. One of the key issues for the early commercialization of WBG and UWBG semiconductor devices is compatibility with Si-device processes. An in-plane junction can be achieved by ion implantation, which is commonly used in Si device fabrication because the damage caused by ion implantation can be repaired by annealing. In the case of nitrides, which are compound semiconductors, there are many types of damage such as anion and cation vacancies as well as interstitials and their complexes. Therefore, the simple annealing technique used in Si device processes can hardly repair damaged WBG and UWBG devices. The formation of low-resistance ohmic contacts, especially p-layers, is one of the key issues for the dynamic stable operation of high-power and high-frequency devices. In the ASPIRE program, Cornell University and Nagoya University are trying to understand the formation mechanism of Mg in GaN intercalated structures and its application to low- resistance ohmic contacts to the p-layers. It is also very important to form an interface between the large-bandgap dielectric and the p-GaN inversion MOS structure with low carrier traps, high stability, and positive threshold voltage to realize high-efficiency high- power devices. In the case of Si, a good and stable MOS structure is easily formed by Si surfaces oxidation. Conversely, if dense carrier traps form between the oxide and p-GaN layers, a good interface of MOS structures cannot be achieved.

In this presentation, the challenges of fabricating GaN, AlN, and AlGaN-based devices in a process compatible with Si devices and the underlying physics in these devices are discussed.
 

Bio: Professor Hiroshi Amano received Doctor of Engineering from Nagoya University. Currently he is a Director, Center for Integrated Research of Future Electronics, and a Professor, Institute of Materials and Systems for Sustainability, Nagoya University.

He shared the 2014 Nobel Prize in Physics with Prof. Isamu Akasaki and Prof. Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources".

He is currently developing technologies for the fabrication of high-efficiency power semiconductor development and new energy-saving devices at Nagoya University.