Vertical 2DHG HHMT Structure for Higher Voltage Blocking
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Solution Overview
Problem
Existing high hole mobility transistors (HHMTs) based on Group III nitride semiconductors face limitations due to defects in their structures, which restrict their application ranges, particularly in high energy, high voltage, and high frequency applications.
Innovation Solution
A high hole mobility transistor with a vertical channel structure is designed, featuring a substrate with a step-shape structure, a channel layer, a channel supply layer forming a vertical two-dimensional hole gas (2DHG) adjacent to the interface, and electrodes positioned on one side of the 2DHG, along with a nucleation layer, buffer layer, and insulating layers to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional planar structure is used for HHMT, then the device structure is simple, but the voltage withstanding capacity is limited and application range is restricted
Solution Approach 1:
The patent transitions from a conventional planar (2D) structure to a vertical (3D) structure by forming a stepped substrate with vertical interfaces. The channel layer and channel supply layer are arranged vertically to create a vertical two-dimensional hole gas (2DHG) at the interface, enabling the transistor to operate in the vertical direction rather than laterally. This dimensional change increases voltage withstanding capacity while maintaining structural feasibility.
Solution Approach 2:
The device is segmented into distinct functional layers: substrate, nucleation layer, buffer layer, channel layer, and channel supply layer. Each layer serves a specific purpose in creating and controlling the vertical 2DHG, allowing independent optimization of each component to achieve high voltage withstanding capacity.
2Adaptability or versatility
If Group III nitride semiconductors are used to form two-dimensional hole gas, then mobility and response speed are high, but defects in existing structures restrict application ranges
Solution Approach 1:
The patent applies local quality by creating a specific (000-1) plane orientation at the vertical interface where the channel layer meets the channel supply layer. This specific crystallographic orientation locally optimizes the interface properties to generate high-quality vertical 2DHG with high mobility and response speed, while the rest of the structure can be optimized separately for different functions.
Solution Approach 2:
The patent introduces intermediary layers (nucleation layer and buffer layer) between the substrate and the active channel region. These intermediary layers mediate the interface between the substrate and the channel structure, reducing defects and improving the reliability of the device while preserving the high mobility characteristics of the Group III nitride semiconductor 2DHG.
3Object-generated harmful factors
If electrodes are positioned on both sides of the vertical two-dimensional hole gas, then current conduction is symmetric, but substrate influence on device performance is increased
Solution Approach 1:
The patent extracts or removes one side of the symmetric electrode configuration, positioning electrodes only on one side of the vertical 2DHG rather than both sides. This asymmetric configuration reduces the substrate's influence on device performance by eliminating the need for electrodes that would require deeper substrate interaction, while still achieving effective current conduction through the vertical hole gas.
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 significantly improves voltage withstanding capacity and reduces dark current, allowing for better performance in high energy and high frequency applications while minimizing the influence of the substrate on the device.
Implementation Method 1
Polar semiconductors have many unique properties. Particularly importantly, fixed polarized charges are present at a surface of the polar semiconductor or at an interface of two different polar semiconductors. These fixed polarized charges may attract movable electrons or hole carriers, thus forming a two-dimensional electron gas 2DEG or a two-dimensional hole gas 2DHG.
Data Source
Figure 1~2A
Figure 2B~2C
Figure 2D~2F
AI summary
The present disclosure relates to a semiconductor device and a method of fabricating the same. The semiconductor device includes: a substrate including a vertical interface; a channel layer disposed outside the vertical interface; and a channel supply layer disposed outside the channel layer; wherein a vertical two-dimensional electron gas 2DEG or two-dimensional hole gas 2DHG is formed in the channel layer adjacent to an interface between the channel layer and the channel supply layer.