T-Gate Transistor With Mini Field Plate for High-Field GaN HEMTs
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Solution Overview
Problem
Transistors with T-gate and gamma-gate structures face challenges in high power and high electric field conditions, leading to current collapse effects in Gallium Nitride HEMT devices and inefficiencies at high frequencies due to capacitive loading.
Innovation Solution
A transistor design featuring a mini field plate and an angled gate stem, which includes a gate structure with three sections: a gate stem, a mini field plate, and a gate top, using metals like Nickel, Platinum, and Gold, and customizable through etching and lithography processes to control the angle and width of the gate stem and mini field plate for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a T-gate structure is used, then frequency response is improved, but performance under high power and high electric field conditions deteriorates
Solution Approach 1:
The gate structure is divided into three distinct sections: gate stem, mini field plate, and gate top. This segmentation allows each part to perform its specific function - the gate stem provides vertical control, the mini field plate manages electric field distribution, and the gate top provides horizontal control, collectively resolving the contradiction between frequency response and high power performance
Solution Approach 2:
The mini field plate acts as an intermediary element between the gate stem and gate top, and also between the gate structure and the channel. It mediates the electric field distribution, preventing direct exposure to high electric fields while maintaining the frequency response benefits of the T-gate structure
2Reliability
If a gamma gate structure is used, then performance under high power conditions is improved, but high frequency efficiency deteriorates due to capacitive loading
Solution Approach 1:
The gate top is positioned at a specific height above the substrate, and the mini field plate has optimized dimensions, creating an optimal balance between electric field management and capacitive loading. This parameter optimization allows the structure to achieve both high power performance and high frequency efficiency
3Reliability
If gate top is positioned closer to substrate, then electric field control is improved, but effective gate length increases due to capacitive loading
Solution Approach 1:
Instead of positioning the gate top closer to the substrate in the vertical dimension, the mini field plate extends laterally to provide electric field control. This dimensional shift allows electric field management without increasing capacitive loading, maintaining effective gate length while achieving field control
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 design enhances the transistor's ability to operate at higher frequencies and voltages, reducing lateral electrical fields and increasing stability, thus overcoming the limitations of prior art T-gate and gamma-gate transistors.
Implementation Method 1
The design enhances the transistor's ability to operate at higher frequencies and voltages, reducing lateral electrical fields and increasing stability
Data Source
AI summary
A transistor and method of fabricating the same comprising a channel layer; an epitaxial barrier layer on the channel layer; an epitaxial cap layer on the epitaxial barrier layer; a dielectric layer on the epitaxial cap layer having an opening through to the epitaxial barrier layer; a gate having angled sidewalls in the opening of the dielectric layer; a mini field plate having angled sidewalls on the gate; and a gate top on the mini field plate, wherein the gate, the mini field plate, and the gate top form a âTâ shape.