GaN Double Gate Transistor for Normally-Off Operation
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Solution Overview
Problem
Gallium nitride (GaN)-based high electron mobility transistors typically have normally-on characteristics, leading to excessive current flow and requiring a negative power supply to turn off, which weakens the electric field and reduces electron concentration in the two-dimensional electron gas region due to piezo-polarization.
Innovation Solution
A field effect semiconductor device with a double gate structure is designed, where the gate electrode is formed on a surface opposite to the source and drain, using a gallium nitride-based semiconductor material with a greater band gap energy, and a method of manufacturing involving a buffer layer, first and second semiconductor layers, and third semiconductor layers is employed to achieve normally-off characteristics and increased breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a GaN-based compound layer is formed substantially thin to obtain normally-off characteristics, then the transistor can be turned off without negative power supply, but the electric field is weakened and electron concentration in the 2D-EG region is reduced
Solution Approach 1:
The patent introduces a vertical dimension by forming a gate electrode on the back surface of the GaN layer opposite to the source-drain surface. This dual-surface gate configuration allows independent control of electric fields at different locations, enabling normally-off characteristics while maintaining strong electric fields and high electron concentration in the 2D-EG region through coordinated gate voltages.
2Speed
If a heterogeneous junction structure is formed with materials having different band gaps to increase electron mobility, then a 2D-EG region is created, but normally-on characteristics occur requiring negative power supply to turn off
Solution Approach 1:
The patent segments the gate control into two independent parts: a front gate on the source-drain surface and a back gate on the opposite surface. This segmentation allows the front gate to maintain the 2D-EG region for high electron mobility while the back gate independently controls the overall conductivity to achieve normally-off characteristics, eliminating the need for negative power supply.
3Ease of manufacture
If a gate electrode is formed on the same surface as source and drain, then fabrication is simplified, but control over the 2D-EG region and electric field distribution is limited
Solution Approach 1:
The patent moves the gate electrode to the back surface of the GaN layer, utilizing the vertical dimension rather than competing for space on the same surface. This spatial separation provides superior control over electric field distribution and 2D-EG region characteristics while maintaining fabrication feasibility through established semiconductor processing techniques.
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 double gate structure and specific layer formation enable normally-off characteristics and a high breakdown voltage, enhancing the electrical performance of GaN-based transistors for high-frequency applications.
Implementation Method 1
an electric field may be weakened due to piezo-polarization, and the concentration of electrons of a 2D-EG region formed in the heterogeneous junction may be reduced
Data Source
AI summary
Field effect semiconductor devices and methods of manufacturing the same are provided, the field effect semiconductor devices include a second semiconductor layer on a first surface of a first semiconductor layer, a first and a second third semiconductor layer respectively on two sides of the second semiconductor layer, a source and a drain respectively on the first and second third semiconductor layer, and a gate electrode on a second surface of the first semiconductor layer.