SiC Junction Barrier Schottky Diode Surge Current Handling
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Solution Overview
Problem
SiC Schottky diodes face limitations in surge current capability due to thermal losses, leading to potential device destruction during high surge currents, and existing JBS diodes suffer from localized overheating during initial surge current concentration.
Innovation Solution
A semiconductor power rectifier design featuring a semiconductor layer with a drift layer, pilot regions, and stripe-shaped emitter regions forming a grid pattern that connects to a transition region, allowing nearly simultaneous switching of p-n junctions to minimize local heat generation during surge currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SiC Schottky diode is used for high-power rectification, then the reverse leakage current is reduced and blocking voltage is increased, but the device is destroyed by heat generation during high surge currents
Solution Approach 1:
The device is segmented into multiple functional regions: a drift layer for voltage blocking, p-n junction regions for surge current handling, and a Schottky junction for low forward voltage drop. Each region is optimized for its specific function, allowing the device to simultaneously achieve high blocking capability and surge current robustness by distributing different tasks to different segments
Solution Approach 2:
The device combines two different junction types (p-n junction and Schottky junction) in a hybrid structure. The p-n junction regions provide high surge current capability with lower thermal losses, while the Schottky junction maintains low forward voltage drop and fast switching. This composite approach allows the device to overcome the limitations of pure Schottky or pure p-n diodes
2Reliability
If a JBS diode is used to improve surge current capability, then blocking characteristics are improved, but localized overheating occurs during initial surge current concentration
Solution Approach 1:
Different regions of the device are given different properties: the p-n junction regions are positioned to handle initial surge current with lower resistance, while the Schottky junction regions provide low forward voltage drop during normal operation. The drift layer is designed with specific doping gradients to control electric field distribution. This local differentiation of properties ensures that surge current is distributed across multiple paths simultaneously, preventing localized overheating
3Reliability
If the p-n junction grid is used in JBS diode, then good blocking characteristics are achieved, but thermal losses occur in the Schottky junction during high surge currents
Solution Approach 1:
The device dynamically switches between different conduction mechanisms based on operating conditions. During normal low-current operation, the Schottky junction dominates with its low forward voltage drop. During surge current conditions, the p-n junction regions activate and provide lower resistance paths, automatically reducing thermal losses. This dynamic adaptation occurs without external control, based on the inherent electrical characteristics of the different junction types
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances surge current capability by ensuring simultaneous switching of p-n junctions, reducing excessive heat generation and improving the rectifier's ability to handle high surge currents without localized overheating.
Implementation Method 1
the electrode layer 21 forms a Schottky contact with the n−-type drift layer 15
Implementation Method 2
the at least one pilot region is connected to the transition region by the plurality of stripe-shaped emitter regions. Connecting the pilot region by the stripe-shaped emitter regions to the transition regions results in a switching on of the first and third p-n junctions nearly simultaneously
Implementation Method 3
the SiC Schottky diode may be destroyed by the heat generation due to thermal losses in the Schottky junction
Data Source
AI summary
A semiconductor power rectifier with increased surge current capability is described. A semiconductor layer includes a drift layer having a first conductivity type, at least one pilot region having a second conductivity type different from the first conductivity type, a plurality of stripe-shaped emitter regions having the second conductivity type, and a transition region having the second conductivity type, wherein the at least one pilot region has in any lateral direction parallel to the first main side a width of at least 200 μm and is formed adjacent to the first main side to form a first p-n junction with the drift layer, each emitter region is formed adjacent to the first main side form a second p-n junction with the drift layer, and the transition region is formed adjacent to the first main side to form a third p-n junction with the drift layer.