The gallium oxide vertical trench gate field effect transistor was developed for the first time! The research group of Professor Long Shibing from the University of Science and Technology of China has made important progress in the field of gallium oxide power electronic devices in cooperation with the processing platform of Suzhou Institute of Nanotechnology, Chinese Academy of Sciences
Recently,
the research group of Professor Long Shibing, School of Microelectronics, University of Science and Technology of China, and the processing platform of Suzhou Institute of Nanotechnology, Chinese Academy of Sciences have made important progress in
the field of gallium oxide power electronic devices . Using oxygen atmosphere annealing and N ion implantation technologies, gallium oxide has been developed for the first time. Vertical Trench Gate Field Effect Transistor .
Power semiconductor devices are the core components in power electronic systems, mainly used for power conversion of power equipment and high power in control circuits. Application scenarios include industrial control, renewable energy and new energy systems, electric vehicles, rail transit, etc.
With the development of new energy vehicles and other industries and their ever-increasing requirements for power system control capabilities, and traditional semiconductor materials such as Si are gradually approaching the physical limit, gallium oxide, as a new generation of power semiconductor materials, has a large bandgap, shock The high cross-field strength is expected to play an important role in the field of power devices in the future.
In addition,
gallium oxide semiconductor materials can be grown by the melt method, and will have more advantages in cost than materials such as SiC and GaN in the future.
At present,
gallium oxide materials are facing an important difficulty :
it is difficult to achieve p-type doping of gallium oxide ,
which leads to problems such as difficulty in realizing enhancement mode and improving power quality factor in gallium oxide field effect transistors. Gallium oxide vertical field effect transistors are suitable for the preparation of high-voltage and high-current devices. Compared with the preparation of horizontal structure MBE samples, the material has a lower cost.
Among the several structures of gallium oxide vertical transistors, although FinFET has excellent performance, the process is difficult and
it is difficult to achieve mass production. Therefore, there is an urgent need
to design a new vertical gallium oxide transistor ,
overcome the current blocking layer technology required by the enhancement transistor, and use the current blocking layer to prepare a newly designed gallium oxide vertical gate transistor.
research work
In the work reported in this report,
the current blocking layer of the device was prepared by oxygen atmosphere annealing and nitrogen (N) ion implantation processes , and gallium oxide that does not require P-type doping technology was developed
in conjunction with the gate groove etching process. Vertical trench field effect transistor structure.
Figure 1 (a) Schematic diagram of the structure of GaO vertical trench gate field effect transistor; (b) Schematic diagram of the working principle of the device; (c) The output curve of N ion implanted transistor; (d) The performance of the reported GaO vertical field effect transistor Compare.
The current blocking layer formed by oxygen atmosphere annealing and N ion implantation can effectively isolate the current path between the source and drain of the transistor. When a positive gate voltage is applied, a conductive channel for electron accumulation will be formed on the side wall of the gate groove, realizing the Current regulation.
Annealing gallium oxide in an oxygen atmosphere can form compensation defects on the surface, thereby forming a high resistance layer. Oxygen atmosphere annealing process is a relatively unique technical means of gallium oxide. This method is inspired by one of the secrets of the success of silicon technology - the oxygen atmosphere annealing of semiconductor silicon.
Similar to silicon annealing in an oxygen atmosphere can form a high-resistance surface layer, gallium oxide uses this method to prepare a current blocking layer (compared to ion implantation), which has the characteristics of fewer defects, no diffusion, and low cost.
N ion implantation MOSFET is based on industrial high-energy ion implantation equipment, adopts N ion implantation doping process, when the N implantation
concentration is 5×10^18cm-3, the threshold voltage of the prepared vertical groove gate MOSFET reaches 4.2V (@1A/cm2) , the saturation current density is as high as 702.3A/cm2, and the on-resistance is 10.4mΩ·cm2 . In addition, by adjusting the concentration of N ion implantation, the breakdown voltage of the device can reach 534V, which is
the highest value of current blocking layer gallium oxide MOSFET devices, and the power quality factor exceeds the theoretical limit of silicon unipolar devices. The two works have found new technical routes and structural solutions for gallium oxide transistors.
