HEMT Barrier Access Regions for Reduced Charge Trapping
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Solution Overview
Problem
Conventional HEMT devices suffer from trapped charges in the barrier layer, leading to signal distortion and reduced switching speed due to charge trapping at the gate contact, which affects the device's performance in high power and high frequency applications.
Innovation Solution
Incorporation of selective modified access regions with a lower surface barrier height than the barrier layer, providing a charge emission path that allows charges to conduct towards the drain contact, reducing the likelihood of charge trapping and improving switching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HEMT devices use a standard barrier layer structure, then the device structure is simple and easy to manufacture, but charge trapping occurs at the gate contact leading to signal distortion and reduced switching speed
Solution Approach 1:
The barrier layer is segmented into multiple distinct layers: a first barrier layer adjacent to the channel and a second barrier layer adjacent to the gate contact. This segmentation allows each layer to be optimized for different functions - the first barrier layer for charge confinement at the interface and the second barrier layer for reduced charge trapping at the gate contact interface, thereby improving switching speed and reducing signal distortion.
Solution Approach 2:
Different regions of the barrier structure are assigned different material compositions and properties. The first barrier layer has specific compositional characteristics optimized for the channel interface, while the second barrier layer has different compositional characteristics optimized for the gate contact interface. This local quality variation addresses the specific charge trapping problem at the gate contact without compromising the overall device structure.
2Reliability
If charges are allowed to accumulate in the barrier layer, then the device structure remains simple, but signal distortion increases and switching characteristics deteriorate
Solution Approach 1:
The barrier layer is divided into a first barrier layer and a second barrier layer with different material compositions. The second barrier layer, being adjacent to the gate contact, is specifically designed to reduce charge trapping, thereby improving signal quality by preventing charge accumulation that would cause distortion.
Solution Approach 2:
The material composition parameters of the barrier layer are changed by introducing a multi-layer structure with different aluminum compositions. The first barrier layer has one compositional range while the second barrier layer has a different compositional range, optimizing charge management and reducing signal distortion through parameter variation.
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 modified access regions enhance switching speed and reduce signal distortion by minimizing charge trapping, thereby improving the device's performance in high power and high frequency applications.
Implementation Method 1
providing a charge emission path that allows charges to conduct towards the drain contact
Implementation Method 2
A major portion of the electrons in the 2DEG may be attributed to polarization in the AlGaN
Data Source
AI summary
A transistor device ac includes a semiconductor epitaxial layer structure including a channel layer and a barrier layer on the channel layer, wherein the barrier layer has a higher bandgap than the channel layer, a source contact and a drain contact on the barrier layer, and a gate contact on the barrier layer between source contact and the drain contact. The device further includes a plurality of selective modified access regions at an upper surface of the barrier layer opposite the channel layer. The selective modified access regions include a material having a lower surface barrier height than the barrier layer, and the plurality of selective modified access regions are spaced apart on the barrier layer along a length of the gate contact.