Gallium nitride device for high frequency and high power applications
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Solution Overview
Problem
The thermal conductivity of silicon substrates in gallium nitride (GaN) devices limits their ability to dissipate thermal energy effectively in high frequency and high power applications, restricting their operational capabilities.
Innovation Solution
A gallium nitride device with a backside field plate is fabricated using a backside processing technique, allowing for the removal of epitaxial layers from a substrate for reuse, and bonding these layers to a high thermal conductivity substrate, enabling efficient heat dissipation and increased power handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon substrates are used in GaN devices, then manufacturing cost is reduced and fabrication is simplified, but thermal conductivity is insufficient for high frequency and high power applications
Solution Approach 1:
The device structure is segmented into two separate substrates: a silicon substrate for epitaxial growth and a separate heat sink substrate for thermal management. This allows each substrate to be optimized for its specific function while working together in the final device assembly.
Solution Approach 2:
A sacrificial layer is introduced as an intermediary between the GaN epitaxial layers and the silicon substrate. This sacrificial layer enables easy separation of the epitaxial structure from the substrate, allowing the GaN layers to be transferred to a heat sink substrate that provides superior thermal conductivity.
2Power
If high power density operation is implemented, then device performance is improved, but thermal energy dissipation becomes insufficient
Solution Approach 1:
The thermal management function is extracted from the silicon substrate and assigned to a dedicated heat sink substrate. This separates the electrical function (performed by the silicon substrate during fabrication) from the thermal function (performed by the heat sink substrate), allowing high power density operation without thermal limitations.
Solution Approach 2:
The final device structure combines GaN epitaxial layers (for high breakdown voltage and high frequency operation) with a heat sink substrate (for superior thermal conductivity). This composite structure enables both high power density operation and effective thermal energy dissipation.
3Productivity
If substrate reuse is implemented, then manufacturing cost is reduced, but processing complexity increases
Solution Approach 1:
A sacrificial layer is deposited on the substrate before epitaxial growth as a preliminary action. This sacrificial layer is specifically designed to be easily removable, enabling substrate reuse without complex processing steps. The presence of this layer from the beginning simplifies the separation process later.
Solution Approach 2:
The sacrificial layer is intentionally designed to be discarded (removed) after serving its purpose of enabling substrate separation. This allows the expensive substrate to be recovered and reused for additional epitaxial growth cycles, significantly reducing manufacturing costs despite the additional processing step.
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 approach enables GaN devices to operate at higher voltages and power densities, reducing costs through substrate reuse and enhancing thermal management, thus addressing the thermal conductivity limitations of silicon substrates.
Implementation Method 1
The backside field plate can help deplete channel electrons and can help distribute an electric field in the GaN device
Implementation Method 2
bonding these layers to a high thermal conductivity substrate, enabling efficient heat dissipation
Data Source
AI summary
A semiconductor device includes a layer of a first semiconducting material, where the first semiconducting material is epitaxially grown to have a crystal structure of a first substrate. The semiconductor device further includes a layer of a second semiconducting material disposed adjacent to the layer of the first semiconducting material to form a heterojunction with the layer of the first semiconducting material. The semiconductor device further includes a first component that is electrically coupled to the heterojunction, and a second substrate that is bonded to the layer of the first semiconducting material.