Dr. Jin-Ping Ao received his BS degree in physics from Wuhan University in 1989, Wuhan, MS degree in semiconductor physics and semiconductor device physics from Hebei Semiconductor Research Institute (HSRI) in 1992, Shijiazhuang, and PhD degree in electronic engineering from Jilin University in 2000, Changchun, China. He joined HSRI in 1992, working on high-speed compound semiconductor devices and integrated circuits, optoelectronic devices and optoelectronic integrated circuits. He joined The University of Tokushima, Japan, in Feb 2001, and currently he is an associate professor involved in the research and development of wide bandgap semiconductor electronic devices, monolithic integrated circuits, chemical sensor and optoelectronic devices. He is also a member of the Thousand Talents Program of China and a specially-appointed professor of Xidian University. He published more than 180 papers in international journals and conferences, owing several related patents. Dr. Ao is a senior member of the IEEE and a member of The Electrochemical Society, The Japan Society of Applied Physics and The Institute of the Electronics, Information and Communication Engineers.
Wireless power transmission using microwave was developed fifty years ago. Recently, it has been attracting much attention owing to the increasing demands for the various wireless technologies, such as electric vehicle power charging, energy harvesting, ubiquitous power source, and wireless power distribution within a building. In the receiving terminal of a wireless power transmission system, which consists of DC/RF conversion, microwave transmission and RF/DC conversion, a so-called rectenna circuit is adopted to complete the RF to DC conversion. The conversion efficiency strongly depends on the performance of the Schottky barrier diode (SBD) used in the rectenna circuit, such as on-resistance, off-capacitance, and turn-on voltage. To improve the efficiency, the reduction of the turn-on voltage to breakdown voltage ratio is very important. As a wide bandgap semiconductor, gallium nitride (GaN) is regarded as a promising material compared with silicon and GaAs to realize high breakdown-voltage, low turn-on voltage to breakdown voltage ratio, and low-resistance devices. However, the turn-on voltage of GaN SBD was about 0.8 V when a Ni electrode was adopted. It is possible to reduce the turn-on voltage by using low work function metals. In this case, attentions should be paid to suppress the leakage current due to the possible interface reaction. Other novel ideas are the proposals of using F-ion implantation or recessed anode technique to realize low turn-on voltage on AlGaN/GaN heterostructure and good results were achieved. We proposed an n--GaN/n+-GaN structure to realize a quasi-vertical structure. By using this structure, low sheet resistance can be expected by adopting the n+-GaN access layer. In this presentation, I will report the fundamentals of GaN SBD and the GaN SBDs for microwave rectification with a low turn-on voltage by using reactively-sputtered TiN as the Schottky electrode.