Invited Speaker

Assoc. Prof. Wei Wang

Xi’an Jiaotong University

E-mail: wei_wang2014@mail.xjtu.edu.cn

Title: Normally-off Hydrogen-terminated Diamond Field-effect Transistor and its Logic Inverter

Profile:

Prof. Wei Wang, Associate Professor, was recruited to work in Xi'an Jiaotong University from 2014. Relying on the Key Laboratory for Physical Electronics and Devices of the Ministry of Education, he mainly carried out research on diamond semiconductor material growth, electronic device research, and proposed to use low power function materials as gate to realize enhanced-mode diamond field effect transistors, which solved the problem of damage to conductive channels by existing technique and improved the electrical characteristics of transistors. As a visiting scholar, he collaborated on surface modification of nanodiamonds at the Department of Human Environment of Kyoto University, proposed the use of long-chain alkyl groups to modify the surface of nanodiamonds to obtain surface hydrophobic nanoparticles, significantly improving the dispersion characteristics of nanodiamonds in organic solvents. In recent years, he have led more than 10 project funded by the National Natural Science Foundation of China, Frontier Innovation Program, Shaanxi Provincial Key R&D Program, and so on. He published over 60 SCI journal papers, such as Carbon, IEEE Electron Device Letters, Applied Physics Letters, applied for over 50 Chinese invention patents, and obtained 14 authorizations. He have been invited multiple times to give presentations at conferences in related fields both domestically and internationally.

Abstract: 

Diamond, considered as the fourth-generation wide band gap semiconductor material, has excellent properties such as large band gap, high breakdown voltage, high mobility, and high thermal conductivity. It has broad application prospects in the fields of high frequency, high power, and high temperature. The diamond normally-off field effect transistor (FET) has the advantages of safety and energy saving. This article proposes the implementation of an enhancement-mode hydrogen terminated diamond FET using a low work function gate. The reason for the normally-off operation is that electrons flow into the hydrogen terminal diamond surface from the low work function material, compensating and depleting the two-dimensional hole gas (2DHG), thereby pinching the channel. The advantage of this technology is that it does not damage the characteristics of 2DHG such as carrier concentration and mobility, avoids the potential interface contamination problem of multi-layer gate deposition, has a simple manufacturing process, and is compatible with industrialized semiconductor processes, which will promote the development of enhancement single crystal diamond FETs. The directly coupled hydrogen-terminated diamond FET logic (DCHDFL) circuit is fabricated. The E-mode and D-mode FETs are assigned as driver and load devices of the DCHDFL circuit to achieve inversion characteristics. The E-mode FET showcases high IDSmax of 53.3mA/mm, VTH of -0.8 V, low SS of 98 mV/dec and on/off ratio of 109, which enable input/output logic level matching with a low drive/load ratio of 1.0. The peak gain of circuit increases from 12.57 to 36.3 V/V with VDD ranging from -5 V to -25 V, which is the highest gain achieved of diamond inverters, due to the high on/off ratio and low SS of E-mode FET. This circuit exhibits proper functions up to 200 °C, demonstrating a good thermal stability. These results indicate the great potential and possibilities for diamond smart power integrated circuit application.