GaN FET Barrier Structure for Independent 2DEG and Threshold Control
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Solution Overview
Problem
Conventional p-doped GaN power transistors face limitations in independently controlling threshold voltage and two-dimensional electron gas (2DEG) characteristics, are sensitive to surface effects, and exhibit reduced current capabilities and low threshold voltage due to parasitic and voltage overshoots.
Innovation Solution
A semiconductor structure with a buffer layer of gallium nitride (GaN) and n-doped GaN source layer, combined with AlGaN barrier layers and p-doped GaN gate layers, allowing for independent optimization of 2DEG characteristics and threshold voltage, with a regrown n-doped GaN source layer enhancing on-state resistance and breakdown capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional p-doped GaN power transistor uses a single AlGaN barrier layer to create 2DEG, then the device can be manufactured with simple structure, but the threshold voltage and 2DEG characteristics cannot be controlled independently
Solution Approach 1:
The single AlGaN barrier layer is segmented into multiple barrier layers (first AlGaN barrier layer and second AlGaN barrier layer) with different thicknesses and aluminum contents. This segmentation allows independent optimization of 2DEG characteristics (controlled by first barrier layer) and threshold voltage (controlled by second barrier layer), resolving the contradiction between structural simplicity and control versatility.
Solution Approach 2:
Different regions of the barrier structure are assigned different local properties: the first AlGaN barrier layer has specific thickness and aluminum content optimized for 2DEG generation, while the second AlGaN barrier layer has different parameters optimized for threshold voltage control. This local quality differentiation enables independent control of electrical characteristics without increasing overall structural complexity.
2Ease of operation
If a conventional p-doped GaN power transistor uses p-doped GaN layer to deplete 2DEG in gate region, then the device achieves normally-off operation, but it becomes highly sensitive to surface effects and parasitic effects
Solution Approach 1:
An undoped or lightly doped GaN layer is introduced as an intermediary between the p-doped gate region and the AlGaN barrier layers. This intermediary layer reduces the direct interaction between the p-doped layer and surface effects, thereby maintaining normally-off operation while reducing sensitivity to surface and parasitic effects, improving overall device reliability.
3Ease of manufacture
If a conventional p-doped GaN power transistor uses thin AlGaN barrier layer, then the manufacturing process is simplified, but the current capabilities are reduced and threshold voltage is low due to parasitic effects
Solution Approach 1:
The barrier structure is segmented into multiple layers with optimized thicknesses. The first AlGaN barrier layer can be thinner for simplified manufacturing, while the second AlGaN barrier layer provides additional control capability. This segmentation allows maintaining manufacturing simplicity while achieving sufficient current capabilities through cumulative effect of multiple layers.
Solution Approach 2:
The device uses a composite barrier structure combining multiple AlGaN layers with different properties rather than a single uniform layer. This composite approach enables optimization of both manufacturing considerations and electrical performance, achieving adequate current capabilities while maintaining practical manufacturability.
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 provides high immunity to dynamic effects, allows for independent control of on-state resistance and threshold voltage, and combines the benefits of GaN lateral and vertical device architectures, improving current capabilities and reducing sensitivity to barrier layer thickness and concentration.
Implementation Method 1
a thin aluminium gallium nitride (AlGaN) barrier layer, which is grown onto a GaN buffer layer in order to create a two-dimensional electron gas (2DEG) at the AlGaN/GaN interface
Implementation Method 2
The 2DEG, a gate module (may also be referred to as a gate metal) is composed of a p-type doped layer
Implementation Method 3
The p-doped GaN layer depletes the two-dimensional electron gas (2DEG) in the gate region and allows fabrication of the conventional enhancement-mode (normally-off) GaN power transistors
Implementation Method 4
a regrown n-doped GaN source layer enhancing on-state resistance and breakdown capabilities
Data Source
AI summary
A member includes a buffer layer made of GaN. The member is characterized in that the member includes a source layer arranged on top of the buffer layer, and the source layer made of n-doped GaN. The member includes a first barrier layer made of Al—GaN arranged over the buffer layer and a first gate layer made of p-doped GaN arranged over the first barrier layer, where the first barrier layer and the first gate layer are arranged adjacent the source layer on one side. The member includes a second barrier layer made of Al—GaN arranged over the buffer layer and a second gate layer made of p-doped GaN arranged over the second barrier layer, where the second barrier layer and the second gate layer are arranged adjacent the source layer on another side. The member enables an independent optimization of the two-dimensional electron gas characteristics and the threshold voltage.