Study Of High Voltage 4H-SiC Junction Barrier Schottky Diode

Wide band-gap semiconductor silicon carbide is the ideal material for powerdevices due to its superior properties and it has been widely researched. 4H-SiC JBS(Junction Barrier Schottky Diode) combines the advantages of PiN and SBD (SchottkyBarrier Diode), that is it has low turn-on voltage, low leakage current, high breakdownvoltage and high switching speed, therefore it can be widely used in the fields of highvoltage and high speed.Focusing on the design of high voltage 4H-SiC JBS, we study the junctiontermination technology (JTT) and novel structures by the two-dimensionalsemiconductor simulator ISE-DESSIS.Breakdown voltage (BV) will decrease severely due to the electric field crowdingeffect, so the junction termination technique is required. In this paper thecommonly-used planar junction termination techniques are discussed, including fieldplate (FP), field limiting rings (FLR) and junction termination extension (JTE). Wedescribe their basic principles and explain in detail the effects of the structuralparameters of each technique on BV. Based on these results, a mixed JTT which is acombination of FP, FLR and JTE is investigated, and simulations demonstrate that it caneffectively improve the reliability and stability of the breakdown voltage.Buried layer in the drift region is also introduced in this paper, and simulationresults show that it can improve BV remarkably and can effectively alleviate thecontradiction between BV and on-resistance. We make detail analysis how the device'scharacteristics are affected by the parameters of the buried layer, such as the position,spacing, overlay accuracy and so on. Lastly another novel structure with the buriedlayer beside the main junction aiming to reduce the reverse leakage current is discussed,and according to the simulations we point out that it should make a tradeoff betweenon-resistance and reverse current when designing the buried layer.