GaN Buffer Doping for HEMT Breakdown Voltage
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face a trade-off between improving breakdown voltage and maintaining device performance due to unintentional doping in GaN buffer layers, which increases leakage current and decreases breakdown voltage, and carbon doping, while attempting to control trap concentrations, affects device performance.
Innovation Solution
Co-doping a region of the carbon-doped GaN buffer layer with silicon to independently control donor and acceptor trap concentrations, optimizing carbon doping for acceptor traps and silicon doping for donor traps, thereby minimizing leakage current and enhancing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon doping is used to increase acceptor trap concentration to improve breakdown voltage, then breakdown voltage increases, but device performance deteriorates due to current collapse and hot electron effects
Solution Approach 1:
The patent divides the single carbon doping function into two separate doping functions: carbon doping provides acceptor traps for breakdown voltage enhancement, while silicon doping provides donor traps for device performance maintenance. This segmentation allows independent optimization of each doping element's concentration and distribution, resolving the trade-off between breakdown voltage and device performance.
Solution Approach 2:
The patent changes the doping parameters by introducing a second dopant (silicon) with different electrical characteristics. By independently controlling acceptor trap concentration (via carbon) and donor trap concentration (via silicon), the system can optimize breakdown voltage without suffering from the performance degradation caused by excessive acceptor traps alone.
2Strength
If high carbon doping concentration is used to achieve significant breakdown voltage improvement, then breakdown voltage increases, but leakage current increases due to self-compensation effects
Solution Approach 1:
Silicon doping acts as an intermediary that mitigates the harmful self-compensation effects of high carbon doping. The silicon-provided donor traps compensate for the excessive acceptor traps from carbon doping, reducing the net positive charge that causes leakage current while preserving the breakdown voltage enhancement from the carbon acceptor traps.
3Strength
If GaN buffer layer is made highly resistive to achieve high breakdown voltage, then breakdown voltage increases, but unintentional doping increases leading to higher leakage current
Solution Approach 1:
The patent changes the electrical parameters of the highly resistive buffer by introducing controlled doping elements (carbon and silicon). Instead of relying on unintentional doping from high resistivity alone, the system uses intentional doping to create specific trap concentrations that achieve both high resistivity and low leakage current through the balanced acceptor-donor trap mechanism.
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 allows for improved breakdown voltage and minimized leakage current in HEMTs by optimizing trap concentrations, reducing the adverse effects of carbon doping on device performance and maintaining high resistivity, thus achieving better performance characteristics.
Implementation Method 1
Carbon (C) is a widely used compensation dopant to increase buffer resistivity and improve breakdown voltage characteristics of the AlGaN/GaN HEMT by reducing buffer leakage. Carbon doping works by introducing deep acceptor traps in the buffer layer.
Implementation Method 2
In some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Implementation Method 3
Donor traps have a major role in delayed avalanche action due to relaxation of the vertical electric field, without which, there is no significant improvement in breakdown characteristics of the device.
Data Source
AI summary
The present invention proposes a set of impurity doping configurations for GaN buffer in an AlGaN/GaN HEMT device to improve breakdown characteristics of the device. The breakdown characteristics depend on a unique mix of donor and acceptor traps and using carbon as a dopant increases both donor and acceptor trap concentrations, resulting in a trade-off in breakdown voltage improvement and device performance. A modified silicon and carbon co-doping is proposed, which enables independent control over donor and acceptor trap concentrations in the buffer, thus potentially improving breakdown characteristics of the device without adversely affecting the device performance.