SiC Thyristor Carrier Injection Layer for Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optically triggered silicon carbide thyristors face challenges with high operating temperatures, requiring high optical power for switching and exhibiting negative temperature coefficients of forward voltage, which can lead to thermal runaway when operated in parallel, and have poor turn-on time and current gain due to thick drift layers.
Innovation Solution
The design includes a silicon carbide thyristor with a carrier injection layer and a buffer layer forming a p-n junction, optimized thickness and doping concentrations to reduce minority carrier injection, and a plurality of optically triggered assistant thyristors to enhance current supply and blocking voltage, achieving a positive temperature coefficient of forward voltage at low current densities and high reverse blocking modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the drift layer is made thick to sustain high reverse blocking voltages, then the reverse blocking capability is improved, but the turn-on time and current gain deteriorate
Solution Approach 1:
The device is segmented into multiple functional layers: the drift layer for voltage blocking, and a separate carrier injection layer for rapid carrier supply. This segmentation allows the drift layer to maintain its thickness for high voltage blocking while the carrier injection layer provides fast turn-on response, resolving the contradiction between reverse blocking capability and turn-on time.
2Power
If conventional silicon carbide thyristors are operated in parallel to increase power handling, then the power handling capability is improved, but thermal runaway occurs due to negative temperature coefficients
Solution Approach 1:
The invention changes the temperature coefficient parameter from negative to positive by optimizing the carrier injection layer thickness and doping concentration. This parameter change ensures that when devices are operated in parallel, the positive temperature coefficient provides automatic current balancing, preventing thermal runaway and enabling reliable parallel operation for enhanced power handling.
3Reliability
If the carrier injection layer is optimized to reduce minority carrier injection at high temperatures, then the temperature coefficient becomes positive, but the optical power required for switching increases
Solution Approach 1:
The carrier injection layer is designed with specific local properties: a thickness of 1-20 micrometers and doping concentration of 1E16 to 1E18 atoms/cm³. These localized quality parameters are optimized to achieve the right balance between reducing minority carrier injection (for positive temperature coefficient) and maintaining sufficient optical switching capability, resolving the contradiction between temperature stability and switching energy.
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 configuration reduces minority carrier injection, improves turn-on characteristics, and enables thyristors to sustain high reverse blocking voltages, preventing thermal runaway and allowing for successful parallel operation with enhanced power handling capabilities.
Implementation Method 1
a thickness of the carrier injection layer and the second doping concentration are selected to reduce minority carrier injection by the carrier injection layer in response to an increase in operating temperature of the thyristor
Implementation Method 2
a plurality of optically triggered assistant thyristors to enhance current supply and blocking voltage
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A thyristor includes a first conductivity type semiconductor layer, a first conductivity type carrier injection layer on the semiconductor layer, a second conductivity type drift layer on the carrier injection layer, a first conductivity type base layer on the drift layer, and a second conductivity type anode region on the base layer. The thickness and doping concentration of the carrier injection layer are selected to reduce minority carrier injection by the carrier injection layer in response to an increase in operating temperature of the thyristor. A cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is thereby reduced.