GaN Transistor Gate Electrode Schottky Barrier Design
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Solution Overview
Problem
High electric fields in AlGaN/GaN transistors lead to charge trapping, limiting their performance and reliability, especially at high temperatures, despite advancements in materials and field plate optimization.
Innovation Solution
The use of a gate electrode made from materials with high Schottky barrier properties, such as platinum (Pt), tungsten (W), molybdenum (Mo), chromium (Cr), or nickel-chromium alloys (NiCr), and polycrystalline indium nitride, combined with spacer layers and field plates, reduces peak electric fields and enhances durability at high temperatures, thereby minimizing degradation and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate materials are used in AlGaN/GaN transistors, then manufacturing is simpler, but charge trapping occurs due to high electric fields, limiting performance and reliability at high temperatures
Solution Approach 1:
The patent changes the material parameter of the gate electrode from conventional metals to materials with high Schottky barrier properties (such as nickel-chromium alloys with barrier heights exceeding 1.0 eV, or polycrystalline indium nitride). This parameter change in Schottky barrier height prevents charge trapping by creating a higher energy barrier that charges cannot easily overcome, thereby improving device reliability at high temperatures while maintaining conventional manufacturing processes.
2Power
If high electric fields are present in the transistor structure, then voltage operation is enhanced, but charge trapping increases, degrading device performance
Solution Approach 1:
The patent converts the harmful effect of high electric fields (which cause charge trapping) into a beneficial configuration by using high Schottky barrier materials. The high electric fields are retained to enable high voltage operation, but the high Schottky barrier gate material prevents these fields from causing charge trapping, thus converting the potential harm into a beneficial high-voltage capability without the associated degradation.
3Device complexity
If conventional gate materials are used, then device structure is simpler, but leakage currents are higher and breakdown voltage is lower
Solution Approach 1:
The patent changes the Schottky barrier height parameter of the gate material to exceed 1.0 eV (compared to conventional materials with lower barriers). This parameter change simultaneously reduces leakage currents by increasing the barrier that prevents carrier injection and increases breakdown voltage by preventing premature avalanche breakdown, all while maintaining a relatively simple gate structure that can be integrated into existing AlGaN/GaN HEMT fabrication processes.
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 solution results in transistors with reduced leakage currents, increased breakdown voltage, and minimal RF output power degradation over time, even at elevated temperatures, ensuring consistent high-performance operation.
Implementation Method 1
The gate comprises a contact portion made from a material having a high Schottky barrier and exhibiting low degradation at high operating temperatures
Data Source
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AI summary
A transistor device capable of high performance at high temperatures. The transistor comprises a gate having a contact layer that contacts the active region. The gate contact layer is made of a material that has a high Schottky barrier when used in conjunction with a particular semiconductor system (e.g., Group-III nitrides) and exhibits decreased degradation when operating at high temperatures. The device may also incorporate a field plate to further increase the operating lifetime of the device.