| As a core component of industrial electronics,wide bandgap semiconductor power electronics are widely used in smart grids,electric vehicles and high-frequency communications.As global energy scarcity becomes increasingly apparent,the desire to achieve sustainable development through technological revolutions and other means has led to technological products that place greater demands on the performance of power electronics.Due to the limitations of silicon(Si),gallium arsenide(GaAs),indium phosphide(InP)and other materials,the performance of the fabricated power devices is approaching the theoretical limit and cannot meet the market demand,while gallium nitride(GaN)materials have a wider bandgap(3.43 eV),higher critical breakdown field strength(3.3 MV/cm)and higher electron mobility(1245 cm/V·s).GaN is the ideal material to break the bottleneck in the development of conventional power electronics.GaN power devices can be divided structurally into lateral and vertical devices.Compared to lateral devices,vertical devices are more suitable for high voltage,low impedance and highly integrated power electronics systems due to their high current expansion capability,high wafer utilization and power density.Currently manufactured vertical GaN Schottky barrier diodes(SBDs)still suffer from high reverse leakage current and breakdown voltage far below theoretical values.The use of trench metal oxide semiconductor(MOS)structure embedded in the Schottky contact region to form trench MOS Schottky barrier diodes(TMBS)can effectively increase the breakdown voltage and reduce the reverse leakage current of SBDs.However,the TMBS device has a high forward on-resistance due to the MOS structure occupying part of the Schottky contact area and the local electric field crowding in the oxide layer at the bottom of the trench MOS structure,which leads to premature breakdown of the device.In order to improve the static characteristics of GaN TMBS devices,the TCAD(Technology Computer Aided Design)techniques is used for structural modelling and numerical simulation in this work.1.To address the problem of premature breakdown of GaN TMBS due to the presence of electric field crowding effect in the oxide layer at the bottom of the trench MOS structure,the embedded p-GaN shielding ring and the vertical guard ring are proposed respectively.The parameters of the p-GaN shielding ring and the vertical guard ring are discussed systematically to mitigate the local electric field crowding effect in the device,thus maximizing the breakdown voltage of the device.The forward conduction characteristics of the device are also analyzed and the Baliga’s figure of merit(BFOM)of the device is calculated using the optimized forward on-resistance and breakdown voltage and compared with the conventional GaN TMBS.2.The trench MOS structure of the GaN TMBS occupies part of the Schottky contact area,resulting in narrowing of the electron conduction channel and increasing the forward onresistance.A core-shell structure and a floating Superjunction diode with a double drift layer are proposed to improve the on-resistance of the device,respectively.The effect of the relevant parameters of the core-shell structure on the regulation of the electron conduction channel is discussed;the mechanism of the concentration ratio of the double drift layer and the spatial distribution of the Superjunction on promoting the charge balance within the drift layer and alleviating the local electric field crowding effect is analyzed.The final result is to ensure that the device is maintained at a high breakdown voltage,so that the forward conduction resistance of the device is as low as possible,resulting in a higher BFOM value and a comprehensive comparison with GaN TMBS diodes. |
