Wide Bandgap JBS Diode Well Region Impurity Density
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Solution Overview
Problem
Wide band gap semiconductor JBS diodes, such as those using silicon carbide, face challenges with high built-in potential leading to uneven current distribution between Schottky and pn diodes, resulting in difficulty in turning on the pn diode and increased risk of overcurrent in the Schottky diode during surge events, which can cause device breakdown.
Innovation Solution
A semiconductor device structure featuring a wide band gap substrate with a drift layer, first and second well regions of different impurity densities and widths, and Schottky and ohmic electrodes, where the surface layer between well regions is depleted in the off-state, allowing for lower bias voltage operation and increased current flow in the pn diode, thereby reducing the risk of overcurrent in the Schottky diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wide band gap semiconductor JBS diode is used, then switching speed is improved, but current distribution becomes uneven and the pn diode becomes difficult to turn on
Solution Approach 1:
The patent applies local quality by creating well regions with different impurity densities (first well regions with higher density and second well regions with lower density) at different locations within the drift layer. This non-uniform doping structure enables different regions to serve different functions: the first well regions facilitate easier pn diode turn-on while the second well regions maintain low off-state current, thereby resolving the contradiction between switching speed and current distribution uniformity in wide band gap semiconductor JBS diodes
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 structure enables high switching speed and resistance to surges, ensuring that surge currents primarily flow through the pn diode, preventing overcurrent in the Schottky diode and enhancing the semiconductor device's reliability.
Implementation Method 1
when the semiconductor device is in an off-state, a surface layer portion of the drift layer that is between the first well regions and is in contact with the Schottky electrode is entirely depleted by a depletion layer expanding from the first well regions adjacent to each other
Data Source
AI summary
In a JBS diode using a wide band gap semiconductor, the wide band gap semiconductor has a large built-in voltage, which sometimes causes difficulties for the pn diode portion to turn on, resulting in a problem that resistance to surge currents is not sufficiently ensured. In order to solve this problem, in the wide-band-gap JBS diode, a pn junction of the pn diode is formed away from the Schottky electrode, and well regions are formed so as to have a width narrowed at a portion away from the Schottky electrode.