Vertical III-Nitride HEMT with Trench 2DEG for High Voltage
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Solution Overview
Problem
High voltage III-Nitride HEMT devices face a design trade-off between on-state resistance and breakdown voltage, with lateral devices becoming less attractive for higher voltage ratings due to increased on-state resistance and chip area, while vertical devices offer reduced cell pitch but lack high mobility 2DEG layers.
Innovation Solution
A vertical HEMT structure is developed with a 2DEG region formed along the trench walls of a recess etched in an epitaxial layer grown on a non-polar III-Nitride substrate, utilizing a carrier supply layer to create a high mobility 2DEG region that supports both on-state and off-state operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a lateral HEMT structure is used with a horizontal drift region to support high voltage, then breakdown voltage is improved, but on-state resistance and chip area increase
Solution Approach 1:
The patent transitions from a lateral HEMT structure with horizontal drift region to a vertical HEMT structure where the drift region extends vertically through the substrate. This dimensional change allows the electric field to be distributed vertically rather than horizontally, enabling high breakdown voltage support with significantly reduced chip area and lower on-state resistance.
Solution Approach 2:
The patent employs a composite material structure consisting of a first III-nitride material layer (e.g., GaN) forming the drift region and a second III-nitride material layer (e.g., AlGaN) forming the barrier layer. This composite structure creates a vertical 2DEG at the interface, combining the high breakdown voltage capability of GaN with the high electron mobility of the 2DEG channel.
2Area of stationary object
If a vertical HEMT structure is used to reduce cell pitch, then chip area is reduced, but high mobility 2DEG layer is lost
Solution Approach 1:
The patent uses a composite material structure with a first III-nitride material layer (e.g., GaN) and a second III-nitride material layer (e.g., AlGaN) with different bandgaps. The interface between these layers forms a vertical 2DEG that provides high carrier mobility while maintaining the vertical structure's area advantages.
Solution Approach 2:
The patent changes the material composition parameters by using a barrier layer with higher aluminum content (e.g., Al0.3Ga0.7N) adjacent to the channel layer. This parameter change creates a sufficient conduction band offset to form a high-density 2DEG with mobility comparable to or exceeding lateral structures, while maintaining the vertical configuration.
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 vertical HEMT structure achieves reduced on-state resistance and increased scalability for high current capability, enabling higher breakdown voltage support with a smaller cell pitch, making it suitable for high voltage applications such as electric vehicles and energy-efficient products.
Implementation Method 1
a 2DEG region formed along said at least a portion of said at least one plane wall of the recess
Implementation Method 2
utilizing a carrier supply layer to create a high mobility 2DEG region
Data Source
AI summary
A HEMT device comprising a III-Nitride material substrate, the surface of which follows a plane that is not parallel to the C-plane of the III-Nitride material; an epitaxial layer of III-Nitride material grown on said substrate; a recess etched in said epitaxial layer, having at least one plane wall parallel to a polar plane of the III-Nitride material; a carrier supply layer formed on a portion of the plane wall of the recess, such that a 2DEG region is formed along the portion of the plane wall of the recess; a doped source region formed at the surface of said epitaxial layer such that the doped source region is separated from said 2DEG region by a channel region of the epitaxial layer; a gate insulating layer formed on the channel region of the epitaxial layer; and a gate contact layer formed on the gate insulating layer.