SiC Rectifier Channel Structure for Leakage Control
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Solution Overview
Problem
Current high voltage diode rectifiers face high reverse bias leakage currents due to low turn-on voltage, leading to thermal runaway, especially at high temperatures or under electrical overload, which can damage the semiconductor device and coupled components.
Innovation Solution
A silicon carbide (SiC) rectifier design with a substrate, drift region, JFET region, body region, anode implant region, and channel structure that maintains low turn-on voltage while minimizing reverse bias leakage by using a channel configured to be off under zero-bias conditions and on at positive turn-on voltage, with charge balance p-bodies to reduce on-state resistance without compromising blocking voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If turn-on voltage is lowered in a diode rectifier, then on-state power loss is reduced, but reverse bias leakage current increases leading to thermal runaway
Solution Approach 1:
The rectifier is segmented into multiple functional regions: a drift region for voltage blocking, a JFET region for channel control, and a body region with anode implant for threshold voltage management. This segmentation allows each region to independently optimize its function, enabling low turn-on voltage without compromising reverse bias performance.
Solution Approach 2:
Different regions of the rectifier are doped with different concentrations and types to create localized electrical properties. The body region has higher doping concentration than the drift region, creating a localized high-field region that controls the channel threshold voltage independently from the overall device turn-on voltage, allowing optimization of both low-state loss and reverse bias leakage.
2Productivity
If turn-on voltage is lowered to reduce power loss, then efficiency improves, but thermal runaway occurs under high temperature and electrical overload
Solution Approach 1:
The body region with its higher doping concentration creates a preliminary counteracting effect by establishing a higher threshold voltage that prevents excessive reverse bias current before thermal runaway can occur. This built-in protective mechanism counteracts the tendency toward thermal runaway that would otherwise result from the lowered turn-on voltage.
Solution Approach 2:
The invention changes the doping concentration parameter locally in the body region to be higher than in the drift region. This parameter change creates a dual-effect device: low overall turn-on voltage for efficiency, but high local threshold voltage to prevent thermal runaway under high temperature and overload conditions.
3Loss of energy
If forward voltage drop is reduced for low turn-on voltage, then on-state resistance decreases, but blocking voltage capability is compromised
Solution Approach 1:
The rectifier structure segments the voltage blocking function (drift region) from the conduction function (JFET channel with body region). The drift region maintains high doping concentration for low on-state resistance and forward voltage drop, while the body region's higher doping creates a threshold effect that preserves blocking voltage capability without increasing forward voltage drop.
Solution Approach 2:
Local quality variations in doping concentration allow the drift region to be optimized for low resistance conduction while the body region provides localized high-field control for voltage blocking. This spatial differentiation of electrical properties enables simultaneous optimization of forward voltage drop and blocking voltage capability.
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 SiC rectifier achieves near-theoretical performance with low turn-on voltage and low on-state resistance, reducing reverse bias leakage and preventing thermal runaway, while maintaining a desired blocking voltage, thus enhancing the reliability and efficiency of high power applications.
Implementation Method 1
A silicon carbide (SiC) rectifier can include a channel of the first conductivity type. The channel can be in contact with and disposed between the JFET region and the anode implant region. The channel can be configured to be off under zero-bias conditions, and on at a positive turn-on voltage.
Implementation Method 2
lowering turn-on voltage in a diode rectifier also lowers an associated energy barrier for reverse bias charge flow (e.g., reduces barrier height). Accordingly, such devices can experience high reverse bias (e.g., leakage) currents and, as a result, enter thermal runaway
Data Source
AI summary
In a general aspect, a silicon carbide (SiC) rectifier can include a substrate of a first conductivity type, a drift region of the first conductivity type, a junction field effect transistor (JFET) region of the first conductivity type, a body region of a second conductivity type, an anode implant region of the first conductivity type, and a channel of the first conductivity type. The channel can be in contact with and disposed between the JFET region and the anode implant region. A portion of the channel between the anode implant region and the JFET region can be disposed in the body region, The channel can be configured to be off under zero-bias conditions, and on at a positive turn-on voltage.