Vertical AlGaN/GaN HEMT Pillar Structure for High Power Density
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Solution Overview
Problem
Existing vertical HEMTs face challenges in achieving high-frequency, high-power, high-temperature, and high-voltage operations while maintaining a small footprint and efficient power density.
Innovation Solution
A vertical high-electron-mobility transistor (HEMT) is designed with a heterojunction formed by an AlGaN-layer and a GaN-layer, featuring a pillar structure with a supporting current blocking layer, and a gate contact arrangement to control the 2DEG channel effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If traditional horizontal HEMT structure is used, then current flow is mediated through 2DEG at heterojunction interface, but device area scaling is limited and footprint is large
Solution Approach 1:
The patent transitions from traditional horizontal planar HEMT structure to a vertical HEMT architecture where the current flow path is reoriented from lateral to vertical direction. The heterojunction interface is positioned vertically between AlGaN and GaN layers, with source and drain contacts arranged at opposite vertical ends, enabling three-dimensional current transport that significantly reduces device footprint while maintaining functionality
Solution Approach 2:
The patent inverts the conventional HEMT configuration by placing the drain contact at the bottom and source contact at the top (or vice versa), reversing the traditional source-drain orientation. This inversion enables vertical current flow through the heterojunction interface, fundamentally changing the device geometry from horizontal to vertical operation mode
2Productivity
If vertical HEMT structure is implemented, then area downscaling is improved, but achieving high-frequency and high-power operation simultaneously is challenging
Solution Approach 1:
The patent employs composite material structure consisting of AlGaN heterojunction layers grown on GaN substrate. The AlGaN/GaN heterostructure provides high electron mobility at the interface while maintaining high breakdown voltage, enabling simultaneous achievement of high-frequency and high-power operation through material composition optimization rather than geometric scaling alone
Solution Approach 2:
The patent implements localized doping regions and heterogeneous layer structures within the vertical channel, with specific AlGaN composition gradients and doping profiles optimized for different vertical positions. The heterojunction interface region is engineered with specific material properties to enhance electron transport, while other regions are optimized for breakdown voltage and thermal management
3Speed
If heterojunction interface is used for current conduction, then high electron mobility is achieved, but breakdown voltage is limited
Solution Approach 1:
The patent implements a nested layered structure where multiple AlGaN/GaN heterojunction interfaces are stacked vertically, with each interface contributing to electron transport while the overall vertical stack provides increased breakdown voltage. The nested arrangement allows simultaneous exploitation of high mobility at interfaces and high voltage tolerance through cumulative layer thickness
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 proposed vertical HEMT achieves improved breakdown voltage, switching speed, and power density, enabling high-frequency and high-power operations while maintaining a compact design.
Implementation Method 1
a heterostructure mesa arranged on the pillar layer, the heterostructure mesa comprising an AlGaN-layer and a GaN-layer, together forming a heterojunction
Implementation Method 2
mediated through the so-called 2-dimensional electron gas, 2 DEG, formed at the interface between the heterojunction of different band gap materials
Implementation Method 3
the at least one vertical pillar is forming an electron transport channel between the drain contact and the heterojunction
Data Source
AI summary
A vertical high-electron-mobility transistor, HEMT (100), comprising: a substrate (310); a drain contact (410), the drain contact being a metal contact via through said substrate; a pillar layer (500) arranged above the drain contact (410) and comprising at least one vertical pillar (510) and a supporting material (520) laterally enclosing the at least one vertical pillar (510); a heterostructure mesa (600) arranged on the pillar layer (500), the heterostructure mesa (600) comprising an AlGaN-layer (610) and a GaN-layer (620), together forming a heterojunction (630); at least one source contact (420a, 420b) electrically connected to the heterostructure mesa (600); a gate contact (430) arranged on said heterostructure mesa (600), and above the at least one vertical pillar (510); wherein the at least one vertical pillar (510) is forming an electron transport channel between the drain contact (410) and the heterojunction (630).