Floating Junction Schottky Barrier Diodes Research Articles

Influence of three-dimensional p-buried layer pattern on the performance of 4H-SiC floating junction Schottky barrier diode

4H-SiC floating junction Schottky barrier diodes (FJ-SBDs) are excellent SiC devices with high Baliga’s figure of merit (BFOM). However, the p-type buried layers in epilayers partially obstruct the current paths, and increase the on-resistance, while the buried layers of dot patterns can reduce the obstruction. In this paper, a three-dimensional (3D) simulation of 4H-SiC FJ-SBDs with dot patterns is reported for the first time. By comparing the results obtained from stripe, square, octagon, and circle patterns, dot patterns are proved to be good choices for buried layers in 4H-SiC FJ-SBDs, and the FJ-SBD with the circle pattern has the highest BFOM of 12.09 GW/cm2, which is 22.62% greater than that of the FJ-SBD with the stripe pattern.

Analytical models of on-resistance and breakdown voltage for 4H-SiC floating junction Schottky barrier diodes

The analytical models of on-resistance and reverse breakdown voltage for 4H-SiC floating junction SBD are presented with the analysis of the transport path of the carriers and electric field distribution in the drift region. The calculation results from the analytical models well agree with the simulation results. The effects of the key structure parameters on specific on-resistance and breakdown voltage are described respectively by analytical models. Moreover, the relationship between BFOM and parameters of floating junction are investigated. It is proved that the analytical models are more convenient for the design of the floating junction SBDs.

Study and optimal simulation of 4H—SiC floating junction Schottky barrier diodes' structures and electric properties

This paper stuides the structures of 4H—SiC floating junction Schottky barrier diodes. Some structure parameters of devices are optimized with commercial simulator based on forward and reverse electrical characteristics. Compared with conventional power Schottky barrier diodes, the devices are featured by highly doped drift region and embedded floating junction layers, which can ensure high breakdown voltage while keeping lower specific on-state resistance, and solve the contradiction between forward voltage drop and breakdown voltage. The simulation results show that with optimized structure parameter, the breakdown voltage can reach 4.36 kV and the specific on-resistance is 5.8 mΩ ·cm2 when the Baliga figure of merit value of 13.1 GW/cm2 is achieved.

Optimized design of 4H-SiC floating junction power Schottky barrier diodes

SiC floating junction Schottky barrier diodes were simulated with software MEDICI 4.0 and their device structures were optimized based on forward and reverse electrical characteristics. Compared with the conventional power Schottky barrier diode, the device structure is featured by a highly doped drift region and embedded floating junction region, which can ensure high breakdown voltage while keeping lower specific on-state resistance, solved the contradiction between forward voltage drop and breakdown voltage. The simulation results show that with optimized structure parameter, the breakdown voltage can reach 4 kV and the specific on-resistance is 8.3 mΩ·cm2.

Doping Concentration Optimization for Ultra-Low-Loss 4H-SiC Floating Junction Schottky Barrier Diode (Super-SBD)

Previous simulation works and experiments on the loss of 4H-SiC floating junction Schottky barrier diodes (Super-SBDs) show that the loss is related to the doping concentration in the drift region and the pattern of the floating layer. The effect of the doping concentration for lowering the loss is characterized the breakdown voltage (Vbd) and the on-state resistances (RonS) of the Super-SBDs based on Baliga’s figure of Merit (BFOM). Experimental devices with two doping concentrations in the drift region are fabricated to investigate the static characteristics: Vbd and RonS. The Vbd of the Super-SBDs is close to the simulation result, near 3000 V. However the tendency of the Vbd by the doping concentration is not similar to the simulation result. And the RonS are about 3.22 mcm2 which is higher than that of simulation result. The doping concentration optimized in this study does not show significant lowering loss and the design of the floating layer in the termination region affect the low-loss static characteristics of the Super-SBD. In addition, adopting PiN structure with floating layer (Super-PiN) affects the low-loss dynamic characteristics, optimizing the doping concentration in the drift region. We conclude that the fabricated Super-SBDs with the floating layer in the termination region, the drift region with a doping concentration of 1.01016 cm-3 and mesa-shaped termination structure, have excellent Vbd of 2990 V which is almost same as that of simulation result and RonS of 3.22 mcm2.

Simulation, Fabrication and Characterization of 4H-SiC Floating Junction Schottky Barrier Diodes (Super-SBDs)

The calculation for 4H-SiC floating junction Schottky barrier diodes (Super-SBDs) was carried out by device simulation and the optimized device structure was fabricated. The best characteristics of the Super-SBDs were breakdown voltage of 2700V and the specific on-resistance of 2.57m*cm2. The world record of Bariga’s Figure of Merit (BFOM) for SiC-SBD expressed by 4Vbd 2/Ron was improved to 11,354MW/cm2.

Fabrication of 4H-SiC Floating Junction Schottky Barrier Diodes (Super-SBDs) and their Electrical Properties

4H-SiC floating junction Schottky barrier diodes (Super-SBDs) were fabricated. It was found that their properties are closest to the theoretical limitation, defined by the relationship between specific on-state resistance and breakdown voltage of 4H SiC-unipolar devices. They have a p-type floating layer designed as line-and-spacing. The specific on-state resistances of Super-SBDs with a few micrometers of spacing width were found to be nearly equal to those of conventional SBDs without p-type floating layer. The breakdown voltages of Super-SBDs were higher than those of conventional SBDs. Accordingly the properties of Super-SBDs have improved the trade-off between specific on-state resistance and breakdown voltage, and the highest value to date for Baliga’s Figure of Merit (BFOM) has been obtained.

Process and Device Simulation of a SiC Floating Junction Schottky Barrier Diode (Super-SBD)

This paper describes process and device simulation results of SiC floating junction Schottky barrier diodes (Super-SBDs). Two-dimensional process simulation of a SiC device is implemented using the customized ISE’s process simulator “DIOS”. The simulation results reproduce the experimentally observed buried floating junction structure of a SiC Super-SBD. The device simulation method using the anisotropic impact ionization coefficients is formulated. The effect of anisotropic avalanche breakdown field on termination structures of SiC SBDs is examined. Finally, by the device simulation we have shown that the trade-off between the on-state resistance and the breakdown voltage of the super-SBD that contains two drift layers exceeds that of the conventional SBD.