Single-Crystal AlN Heat Spreader for III-Nitride HEMT Junction Cooling
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Solution Overview
Problem
Traditional III-N high-electron-mobility transistors face catastrophic failure due to unmanageable junction temperatures without effective heat dissipation, and existing top-side epitaxial heat spreader solutions result in amorphous or polycrystalline layers compromising thermal transport.
Innovation Solution
A thermal management device with a single crystal epitaxially grown AlN layer on top of a substrate, lattice-matched to a pseudomorphic channel layer, and a backside heat sink for efficient heat dissipation, allowing thick AlN layers without relaxation and thermal transport compromise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thick AlN layers are grown on non-native substrates to improve thermal transport, then thermal conductivity is improved, but the layers become amorphous or polycrystalline compromising thermal transport
Solution Approach 1:
A native AlN substrate serves as an intermediary layer between the non-native substrate and the thick AlN heat spreader layer. This intermediary enables the growth of thick single-crystal AlN layers by providing a lattice-matched foundation, allowing thermal transport to be maintained while achieving the necessary thickness for effective heat dissipation.
Solution Approach 2:
The thermal management structure is segmented into multiple functional layers: a native AlN substrate layer for crystal growth, a thick AlN heat spreader layer for thermal transport, and integration with the GaN HEMT device structure. This segmentation allows each layer to be optimized for its specific function while maintaining overall system performance.
2Reliability
If AlN is grown thicker to annihilate threading dislocations and improve epitaxial film quality, then charge transport quality is improved, but thermal transport is compromised due to layer relaxation
Solution Approach 1:
The native AlN substrate acts as a mediator that decouples the requirements for thick layer growth (for dislocation annihilation) from the requirements for maintaining crystalline quality (for thermal transport). By providing a lattice-matched foundation, it enables thick single-crystal AlN growth without relaxation-induced defects.
3Temperature
If top-side epitaxial heat spreader layers are applied to dissipate heat, then heat dissipation is improved, but RF losses increase or device damage occurs
Solution Approach 1:
The heat spreader functionality is localized to the top-side AlN region directly above the heat-generating junction, while the channel and barrier layers maintain their optimized composition and thickness for RF performance. This localized approach allows heat dissipation enhancement without compromising the electrical characteristics of the active device regions.
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 solution enables efficient heat spreading from the transistor junction, reducing thermal resistivity and extending the lifespan of RF systems by using single crystal AlN for top-side heat dissipation without interfering with high-frequency operation.
Implementation Method 1
an epitaxially grown layer on top of at least a portion of the barrier layer, wherein the epitaxially grown layer is operative to disperse heat from a contact touching at least the epitaxially grown layer
Implementation Method 2
single crystal epitaxially grown AlN layer on top of a substrate
Implementation Method 3
a backside heat sink for efficient heat dissipation
Data Source
AI summary
Techniques, a system, and architecture are disclosed for top side transistor heat dissipation. The heat dissipation is done through single crystal epitaxially grown layer such as AlN. The architecture may include a back side heat sink to increase thermal dissipation as well. The architecture may further include a pseudomorphic channel layer that is lattice matched to the substrate.