GaN HEMT AlGaN Buffer Electron Affinity Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional GaN-based HEMTs experience a significant drop in drain current during high-frequency signal off-time, leading to a drift phenomenon that hinders quick recovery and stable output, affecting the intermittent on/off operation in high-frequency applications.
Innovation Solution
The structure of the GaN-based HEMT is modified by incorporating an AlGaN layer with a higher electron affinity than the AlN layer, and another AlGaN layer with an even higher electron affinity, creating a barrier that prevents electrons from reaching traps in the i-GaN layer, thereby reducing the drift phenomenon and enabling quicker recovery of the drain current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional GaN-based HEMT structure with AlN buffer layer is used, then high breakdown voltage is achieved, but drain current drops excessively during off-time causing output drift
Solution Approach 1:
The buffer layer is segmented into multiple AlGaN layers with different Al compositions (first AlGaN layer with higher Al content, second AlGaN layer with lower Al content) separated by a GaN layer. This segmentation creates distinct electron affinity barriers that prevent electron leakage to traps while maintaining high breakdown voltage, resolving the contradiction between reliability and current stability.
Solution Approach 2:
Different regions of the buffer layer are assigned different local qualities through varying Al compositions. The first AlGaN layer has higher Al content for stronger electron confinement, the GaN layer provides a transition region, and the second AlGaN layer has lower Al content for optimized electron transport. This local quality variation simultaneously achieves high breakdown voltage and stable drain current.
2Productivity
If high-frequency signal on/off switching is performed frequently, then current efficiency is improved, but drain current recovery time becomes excessively long
Solution Approach 1:
The multi-layer buffer structure with varying electron affinities is configured in advance to create pre-established electron barriers. When high-frequency switching occurs, these pre-configured barriers immediately prevent electron leakage to traps, enabling rapid drain current recovery without requiring long stabilization periods, thus reducing time loss while maintaining current efficiency.
3Ease of manufacture
If AlN layer with uniform electron affinity is used, then manufacturing is simplified, but electron leakage to traps occurs causing output drift
Solution Approach 1:
The buffer layer uses a composite structure of multiple AlGaN layers with different Al compositions and a GaN layer. This composite material approach creates varying electron affinity barriers that effectively block electron leakage to traps. While more complex than uniform AlN, the composite structure can be manufactured using standard MOVPE techniques by controlling Al/Ga ratio during sequential layer deposition, achieving a balance between manufacturing feasibility and electron leakage prevention.
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
This configuration significantly reduces the drop in drain current when switching from on to off, allowing for faster operations and quicker recovery of the drain current, thereby improving the stability and efficiency of high-frequency signal handling.
Implementation Method 1
incorporating an AlGaN layer with a higher electron affinity than the AlN layer, and another AlGaN layer with an even higher electron affinity, creating a barrier that prevents electrons from reaching traps in the i-GaN layer
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A compound semiconductor device is provided with a substrate (1), an AlN layer (2) formed over the substrate (1), an AlGaN layer (3) formed over the AlN layer (2) and larger in electron affinity than the AlN layer (2), another AlGaN layer (4) formed over the AlGaN layer (3) and smaller in electron affinity than the AlGaN layer (3). Furthermore, there are provided an i-GaN layer (5) formed over the latter AlGaN layer (4), and an i-AlGaN layer (6) and an n-AlGaN layer (7) formed over the i-GaN layer (5).