SiC JBS Diode Surge Handling via Minority Carrier Injection
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Solution Overview
Problem
Silicon carbide Junction Barrier Schottky (JBS) diodes face challenges in handling current surges, leading to potential catastrophic failure due to thermal runaway, and existing designs that mitigate this often increase on-state resistance at lower currents.
Innovation Solution
The diode structure includes stripe-shaped p+ regions and surge protection regions formed by ion implantation, which inject minority carriers at high current densities to reduce resistance during surges, while maintaining low resistance at normal operating conditions through strategically designed doping and depth of these regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surge protection regions are added to handle current surges, then reliability during surges is improved, but device complexity increases
Solution Approach 1:
The patent combines the surge protection function with the existing JBS diode structure by integrating surge protection regions into the drift layer. The p-n junctions formed by implanting opposite-type dopants in the drift layer serve dual purposes: maintaining normal Schottky diode operation at low currents and providing surge protection at high currents, thereby merging two functions into a single integrated structure.
Solution Approach 2:
The surge protection regions are strategically positioned in specific areas of the drift layer where surge currents are most likely to flow. By localizing the surge protection function to specific regions rather than uniformly across the entire device, the patent provides effective surge handling while minimizing the increase in overall device complexity.
2Reliability
If p-n junctions are formed for surge protection, then current surge handling is improved, but on-state resistance increases at lower currents
Solution Approach 1:
The patent designs the surge protection regions to be dynamically activated only when needed. The p-n junctions remain in a high-impedance state during normal low-current operation, effectively disconnecting themselves from the current path. When surge currents occur, the junctions turn on and provide low-impedance paths for surge current diversion, thus achieving dynamic adaptation to different operating conditions.
Solution Approach 2:
The patent carefully controls the doping concentration and depth of the surge protection regions to ensure they have high resistance at normal operating voltages but low resistance when activated by surge currents. By adjusting dopant concentration and junction depth parameters, the surge protection regions maintain minimal impact on on-state resistance at low currents while providing effective surge protection at high currents.
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
This design effectively reduces power dissipation and prevents forward current runaway during current surges, enhancing the diode's ability to handle high currents without increasing on-state resistance at lower currents.
Implementation Method 1
stripe-shaped p+ regions and surge protection regions formed by ion implantation, which inject minority carriers at high current densities to reduce resistance during surges
Implementation Method 2
A metal anode contact 18 is formed on the surface of the n- drift layer 14 in contact with both the n- drift layer 14 and the p+ regions 16. The anode contact 18 forms a Schottky junction with the exposed portions of the drift layer 14
Implementation Method 3
Under reverse bias conditions, however, the depletion regions formed by the PN junctions J2 between the p+ regions 16 and the drift layer 14 expand to block reverse current through the device 10
Implementation Method 4
A plurality of p+ regions 16 are formed, typically by ion implantation, in the surface of the n- drift layer 14
Data Source
Figure 1~6
Figure 2~3
Figure 4~5
AI summary
An electronic device includes a silicon carbide drift region having a first conductivity type, a Schottky contact on the drift region, and a plurality of junction barrier Schottky (JBS) regions at a surface of the drift region adjacent the Schottky contact. The JBS regions have a second conductivity type opposite the first conductivity type and have a first spacing between adjacent ones of the JBS regions. The device further includes a plurality of surge protection subregions having a second conductivity type. Each of the surge protection subregions has a second spacing between adjacent ones of the surge protection subregions that is less than the first spacing.