Wide Bandgap Semiconductor Rectifier Reducing Hole Injection Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor rectifiers with high-endurance-voltage levels, such as those using silicon carbide, face challenges in reducing the hole injection voltage, leading to increased resistance and breakdown probability due to heat generation during forward surge currents.
Innovation Solution
The semiconductor rectifier design incorporates a wide bandgap semiconductor substrate with specific impurity regions and electrode configurations, including a wide p+-type impurity region of 15 μm or more, and a RESURF region, to reduce the hole injection voltage and enhance conductivity modulation, thereby improving surge current resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional high-endurance-voltage semiconductor rectifier designs are used, then voltage blocking capability is improved, but hole injection voltage increases leading to higher resistance and breakdown probability
Solution Approach 1:
The patent applies local quality by creating a p+-type impurity region with high doping concentration (1E+19 to 1E+21 atoms/cm³) localized at the interface between the n-type drift layer and the Schottky contact. This localized high-doping region modifies the electric field distribution specifically at the critical interface area, enabling conductivity modulation that reduces on-state voltage and hole injection voltage without compromising the overall voltage blocking capability of the device structure.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the doping concentration of the p-type impurity region to be significantly higher (1E+19 to 1E+21 atoms/cm³) than conventional designs, and by optimizing its depth (0.1 to 2.0 μm) and lateral dimensions. These parameter modifications enable the formation of a strong p-n junction that facilitates efficient minority carrier injection and conductivity modulation, thereby reducing resistance and breakdown probability while maintaining high voltage blocking capability.
2Productivity
If forward surge current flows through the semiconductor rectifier, then current discharge capability is improved, but heat generation increases causing crystal or junction breakdown
Solution Approach 1:
The patent applies parameter changes by optimizing the p-type impurity region with high doping concentration (1E+19 to 1E+21 atoms/cm³) and controlled depth (0.1 to 2.0 μm), which enables efficient conductivity modulation. This allows the device to discharge large forward surge currents with reduced on-state voltage, thereby suppressing heat generation energy (current×voltage) and preventing thermal breakdown while maintaining high current discharge capability.
Solution Approach 2:
The patent converts the potentially harmful effect of high current flow into a beneficial effect by utilizing conductivity modulation through the p-type impurity region. The high doping concentration enables efficient minority carrier injection that reduces on-state resistance dynamically during surge current flow, transforming the heat-generating current into a mechanism that actually reduces voltage and suppresses heat generation.
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 the hole injection voltage, suppressing heat generation and lowering the breakdown probability, enabling a high-endurance-voltage semiconductor rectifier with improved surge current resistance and operational efficiency.
Implementation Method 1
The wide bandgap semiconductor has a band gap wider than that of Si, and has a breakdown electric field strength and a heat conductivity which are higher than those of Si. By utilizing the characteristics, a power semiconductor device with low loss and capable of operating at a high temperature can be realized.
Implementation Method 2
a Merged PiN-diode Schottky-diode (MPS) in which a contact between an impurity region (for example, p-type) and a metal in a JBS is made an ohmic contact or close to an ohmic contact so as to cause minority carrier injection when a voltage exceeding a built-in potential (Vbi) between the impurity region and the semiconductor layer is applied, thereby obtaining a decrease of a resistance due to the conductivity modulation is known.
Implementation Method 3
When a current larger than that in a stationary state flows into the MPS, the current causes crystal breakdown or junction breakdown of an electrode or the like by heat generation based on the energy equation: current×voltage=energy.
Data Source
AI summary
A semiconductor rectifier includes a first conductivity type wide bandgap semiconductor substrate having a first conductivity type wide bandgap semiconductor layer on an upper surface of which is formed a plurality of first wide bandgap semiconductor regions of the first conductivity type sandwiching a plurality of second wide bandgap semiconductor regions of a second conductivity type, and a plurality of third wide bandgap semiconductor regions of the second conductivity type, at least a part of the third wide bandgap semiconductor regions being connected to the second wide bandgap semiconductor regions and each of the third wide bandgap semiconductor regions having a width smaller than that of the second wide bandgap semiconductor regions. A first electrode is formed on the first and second wide bandgap semiconductor regions and a second electrode is formed on a lower surface of the wide bandgap semiconductor substrate.