GaN on Diamond Substrates via Nucleating Layer
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Solution Overview
Problem
Existing thermal management systems for high-power electronic and optoelectronic devices, particularly those using gallium nitride, face challenges in efficiently dissipating heat due to parasitic resistances and inefficiencies, leading to limited thermal performance and reliability issues.
Innovation Solution
The use of synthetic diamond films as heat spreading layers, combined with wide-gap semiconductor technology, to create a freestanding diamond substrate with a gallium nitride layered structure, which enhances thermal conductivity and reduces temperature rise in devices, thereby improving heat spreading and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional substrates (silicon, sapphire, silicon carbide) are used for GaN devices, then device manufacturing is feasible, but thermal performance is limited due to insufficient heat dissipation
Solution Approach 1:
The patent changes the substrate material parameter from conventional options (silicon, sapphire, silicon carbide) to diamond, which has superior thermal conductivity. This parameter change enables more efficient heat dissipation, reducing device operating temperature and improving reliability under high power conditions while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs a composite structure combining diamond substrate with GaN epilayers and intermediate nucleating layers. This composite material approach leverages the exceptional thermal properties of diamond while maintaining the electrical and structural requirements of GaN devices, achieving both thermal performance and device functionality
2Manufacturing precision
If GaN is grown directly on substrate, then device structure is simplified, but lattice mismatch causes dislocations and reduces device quality
Solution Approach 1:
The patent introduces an intermediate nucleating layer as a mediator between the diamond substrate and GaN epilayers. This intermediate layer serves as a transition interface that accommodates lattice mismatch, reduces dislocation density, and enables high-quality GaN growth while maintaining a relatively simple overall device structure
Solution Approach 2:
The patent changes the growth interface parameters by introducing the intermediate nucleating layer, which has specific crystallographic and chemical properties that facilitate epitaxial growth. This parameter change at the interface level improves GaN layer quality without significantly complicating the device architecture
3Temperature
If synthetic diamond films are used for heat spreading, then thermal conductivity is enhanced, but manufacturing complexity increases due to additional processing steps
Solution Approach 1:
The patent merges the heat spreading function with the substrate itself by using synthetic diamond as the substrate material. This integration eliminates the need for separate heat spreading layers and reduces the number of fabrication steps, improving ease of manufacture while maintaining superior thermal conductivity and heat dissipation efficiency
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 results in a significant reduction in device temperature, enhancing the lifespan and performance of high-density heat sources in applications like microwave transistors and light-emitting diodes, with a 50% improvement in temperature reduction demonstrated in stripe chip calculations.
Implementation Method 1
growth of synthetic diamond epilayers on an intermediate nucleating layer
Implementation Method 2
enhances thermal conductivity and reduces temperature rise in devices, thereby improving heat spreading
Data Source
AI summary
Methods for integrating wide-gap semiconductors with synthetic diamond substrates are disclosed. Diamond substrates are created by depositing synthetic diamond onto a nucleating layer deposited or formed on a layered structure including at least one layer of gallium nitride, aluminum nitride, silicon carbide, or zinc oxide. The resulting structure is a low stress process compatible with wide-gap semiconductor films, and may be processed into optical or high-power electronic devices. The diamond substrates serve as heat sinks or mechanical substrates.