Design Of 100V Lateral Bootstrap Diode With Optimized Reverse Recovery Characteristics

The GaN-based power devices show the advantages of higher critical electric field,higher switching frequency and higher mobility.Therefore,they are widely used in high-frequency power systems,in which bridge topology is often used.In bridge circuits,GaN-based power devices need to be driven by high-speed and highly reliable gate drive IC.The bootstrap diode is the key component of bootstrap circuits in the gate drive IC.The characteristics of the bootstrap diode strongly affect the performances of the gate drive IC.Therefore,it is significant to optimize the bootstrap diode.Based on the silicon-based bootstrap diode that has been manufactured,forward voltage drop,reverse recovery speed and reverse recovery reliability have been further optimized.It is found that reverse recovery failure under high d I/dt condition is caused by severe electric field strength at the anode side.Low commutating d I/dt in the final phase of reverse recovery process greatly increase the reverse recovery time.In the proposed structure,floating P+ dynamic field limiting rings are adopted to suppress the peak of electric field at the anode side.Moreover,the concept of highly doped N-type buried layer is implemented to improve the forward voltage drop and reverse recovery time.Furthermore,an anode region with lower doping concentration and less P+ regions is utilized to achieve low injection efficiency.This results in faster reverse recovery speed.The simulation results demonstrate that forward voltage drop,breakdown voltage and reverse recovery time of the improved structure is 0.87 V,157V and 39 ns,respectively.In addition,the proposed structure can work safely with d I/dt of 350A/μs,its reverse recovery ruggedness has been greatly improved.