Design And Optimization Of New Structure Of GaN-based Vertical JFET Power Device

As the representative of the third generation of wide band gap semiconductor materials,GaN has great potential in the field of power semiconductors due to its advantages such as wide band gap,high critical breakdown electric field and high thermal conductivity.On the one hand,the development of GaN-on-Si has significantly reduced the cost of GaN devices,which is a milestone for the application and development of GaN material.On the other hand,since GaN devices are planar devices,they are highly compatible with existing Si semiconductor processes,which makes it easier to integrate with other semiconductor devices.Because of this,the research on GaN devices is receiving more and more attention.After the development of GaN devices for more than 30 years,the research on lateral AlGaN/GaN HEMT devices is relatively mature,and the disadvantages of lateral devices are becoming more and more well known.1)Traditional lateral GaN HEMT devices can cause a series of stability issues such as current collapse.2)The breakdown of the lateral GaN HEMT device due to the concentrated channel electric field distribution.Aiming at the shortcomings of lateral devices,this paper respectively studies GaN VJFET devices with intrinsic reverse conduction characteristics and the breakdown mechanism and structural optimization design of GaN VJFET devices from the perspective of vertical JFET devices.1.We propose a novel enhancement-mode vertical GaN JFET power device that integrates a reverse recovery Schottky barrier diode(SBD).By embedding the reverse recovery diode and separating the forward and reverse current conduction path,the intrinsic reverse conductance functionality of the GaN vertical JFET are achieved.The Sentaurus TCAD was used to simulate the forward and reverse characteristics of the proposed GaN VJFET.The results show that the threshold voltage of the forward VJFET is 2.0 V,the breakdown voltage is 1720 V,and the specific resistance is 2.79 m?·cm~2,and the turn-on voltage of the reverse SBD is 0.7 V.The new GaN JFET structure proposed in this paper has great potential in the field of power semiconductors.2.The breakdown mechanism of traditional GaN VJFET devices is studied deeply,and a new structure of PI-VJFET(P-GaN Island-Vertical Junction Field Effect Transisitor)is proposed based on this.The characteristics of the PI-VJFET device are:(1)The introduction of a P island structure in the JFET region effectively reduces the on-resistance of the device.From the simulation results,it is known that the on-resistance of the PI-VJFET structure is about 50%of the traditional GaN VJFET;(2)The P island structure is extended from the JFET channel region to the drift region of the device,which makes the electric field distribution in the device more uniform,thereby effectively improving the breakdown voltage of the device.It can be known from the simulation results that the breakdown voltage of the proposed PI-VJFET is 1400 V,which is about500 V higher than the conventional structure.In addition,the structural parameters of the P island are optimized and analyzed in this paper.The proposed PI-VJFET structure is of great significance for improving the breakdown voltage of GaN vertical JFET.