SiC Bipolar Devices with Gallium Doped Base
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Solution Overview
Problem
High-power silicon carbide bipolar junction transistors (BJTs) face challenges in achieving high current gain while maintaining near-theoretical blocking voltage and on-state resistance, as reducing acceptor dose in the base region to improve current gain leads to degraded blocking voltage due to early punch-through.
Innovation Solution
The implementation of a silicon carbide power semiconductor device with a base region predominantly doped with gallium, incorporating a multi-layer base region structure with gallium and aluminum doping, and an Ohmic contact with aluminum-doped sub-contact regions to enhance current gain and reduce base resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acceptor dose in the base region is reduced to improve current gain, then current gain is improved, but on-state resistance increases
Solution Approach 1:
The multi-layer base structure creates local variations in doping concentration, where higher-doped regions provide charge carriers for lower on-state resistance while lower-doped regions enhance current gain. This spatial differentiation of doping quality allows simultaneous optimization of both current gain and on-state resistance.
Solution Approach 2:
The invention changes the doping concentration parameter across different base layers, creating a gradient from higher doping in the first base layer to lower doping in subsequent layers. This parameter variation enables the device to achieve improved current gain while maintaining acceptable on-state resistance through the combined effect of all layers.
2Reliability
If multi-layer base region structure with gallium and aluminum doping is implemented, then current gain and blocking voltage are improved, but device complexity increases
Solution Approach 1:
The base region is segmented into multiple discrete layers, each with specific doping concentrations and compositions. The first base layer has distinct properties from the second, third, and subsequent base layers. This segmentation allows independent optimization of each layer's characteristics to achieve superior overall device performance while managing complexity through systematic layer design.
Solution Approach 2:
The base region employs composite materials with different doping compositions (gallium and aluminum) across multiple layers. This composite structure enables tailored electrical properties in each layer, achieving high current gain and blocking voltage while the systematic composition variation provides a manageable approach to the increased structural complexity.
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 approach achieves increased current gain while retaining near-theoretical blocking voltage and reducing on-state resistance, improving the performance of high-power BJTs for high-temperature and high-frequency applications.
Implementation Method 1
The base region can include p-type SiC doped with gallium
Implementation Method 2
The sub-contact region can be doped with aluminum
Data Source
AI summary
In a general aspect, a power semiconductor device can include a collector region disposed on a substrate, the collector region can include n-type silicon carbide (SiC). The power semiconductor device can also include a base region disposed on the collector region. The base region can include p-type SiC doped with gallium. The power semiconductor device can include an emitter region disposed on the base region. The emitter region can include n-type SiC carbide.