Hybrid GaN HEMT Drain Contact for Current Collapse Mitigation
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Solution Overview
Problem
GaN-based high electron mobility transistors (HEMTs) suffer from current collapse due to electron trapping during high-voltage switching, leading to increased dynamic on-state resistance and reliability issues, which are exacerbated by the use of multiple p-type drain contact structures that can reduce channel width and increase static resistance.
Innovation Solution
A hybrid drain contact structure is introduced, comprising both an ohmic contact and a p-type drain contact with two or more junctions having different energy barrier heights, formed by a p-type semiconductor layer and metal portions, to efficiently inject holes and neutralize trapped electrons, thereby mitigating current collapse and reducing dynamic on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple p-type drain contact structures are used to mitigate current collapse, then electron trapping is reduced, but channel width is reduced and static resistance increases
Solution Approach 1:
The patent applies local quality by creating different junction types at different locations within the drain contact structure. Specifically, it forms a first junction with a first energy barrier height and a second junction with a second energy barrier height lower than the first, allowing each region to perform its specialized function optimally while maintaining overall device performance
2Reliability
If multiple p-type drain contact structures are used to mitigate current collapse, then electron trapping is reduced, but static on-state resistance increases
Solution Approach 1:
The patent changes the energy barrier height parameter across different junctions within the drain contact structure. By having a first junction with a first energy barrier height and a second junction with a lower second energy barrier height, the structure optimizes hole injection efficiency while reducing the overall static on-state resistance compared to uniform high-barrier structures
3Reliability
If multiple p-type drain contact structures are used, then hole injection is improved, but device layout complexity increases
Solution Approach 1:
The patent merges multiple junctions into a single integrated drain contact structure. The first junction and second junction are combined within the same drain contact, allowing the structure to provide both high hole injection efficiency and simplified layout compared to using separate discrete contact structures
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 hybrid drain contact structure improves hole injection efficiency, reduces voltage drop, and simplifies layout, resulting in stable drain current and reduced static on-state resistance without compromising breakdown voltage.
Implementation Method 1
The second drain contact includes a first metal portion and a second metal portion, where the first metal portion and the first semiconductor portion form a first junction having a first energy barrier height, and the second metal portion and the second semiconductor portion form a second junction having a second energy barrier height lower than the first energy barrier height.
Data Source
AI summary
A semiconductor device, such as a GaN-based high electron mobility transistor (HEMT), includes a hybrid drain contact structure over a channel layer and a barrier layer. The hybrid drain contact structure includes a first drain contact electrically coupled to the channel layer, a semiconductor layer over the barrier layer and including a first semiconductor portion and a second semiconductor portion, and a second drain contact on the semiconductor layer and electrically coupled to the first drain contact. The second drain contact includes a first metal portion and a second metal portion. The first metal portion and the first semiconductor portion form a first junction having a first energy barrier height. The second metal portion and the second semiconductor portion form a second junction having a second energy barrier height lower than the first energy barrier height.