IEEE Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia 2018)

195 / 2017-12-06 21:20:45

Vertical GaN MOSFETs with Over 1.6 kV breakdown voltage :A theoretical studying

GaN,mosfet,breakdown voltage,vertical stracture

Plenary track > Device structures and fabrication techniques

Owing to its high breakdown electric field, excellent frequency characteristics, high electron drift velocity and so on, Gallium Nitride (GaN)has a great utilization potential in developing high-voltage high-power semiconductor devices. Because of the poor conductivity of the substrate or the AlN nucleation, the longitudinal conductivity of heteroepitaxial GaN material structure is not good enough. Traditionally, most GaN MOSFETs are studied using lateral structures. However, there is always a contradiction between the breakdown voltage and the area of the device, so the lateral structure does not apply to the requirements of higher pressure and device miniaturization.
In this paper, a GaN MOSFET device on a free-standing GaN substrate has been investigated. The optimization and simulation of the device structure are carried out in order to obtain the device characteristics of high voltage and high power. We design the GaN MOSFETs structure through SILVACO platform. Influence of the key parameters on the DC characteristics are investigated, such as the doping concentration of the drift and body region, the length of the drift region. The breakdown characteristics are analyzed emphatically. We find that with the increase the bulk region doping concentration ,the breakdown voltage also increases. The reason is that the increasing doping concentration can reduce the avalanche current. The analysis shows that the breakdown voltage of the vertical GaN MOSFET device can also be improved by reducing the doping concentration or increasing the length of the drift region. Design of the high voltage GaN MOSFETs is also be optimized, the doping concentration of p-GaN region is set to 9 × 1016 cm-3; the doping concentration of n-GaN drift layer is 2 × 1015 cm-3; the device on-resistance is 125 mΩ • cm and the breakdown voltage is up to 1602 V.