Light Emitting Device Thermal Management via Segmented Heat-Sink
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of sapphire substrates in semiconductor light-emitting devices leads to issues such as mechanical stress, damage to multi-layered light-emitting structure thin films, poor thermal conductivity, and limitations in chip size and heat dissipation, which restrict the performance and yield of LEDs, especially in large area and high current applications.
Innovation Solution
A supporting substrate with a thermal expansion coefficient similar to sapphire, combined with a sacrificial layer and thick metal films, is used to absorb mechanical stress and enhance bonding, allowing for a stable heat-sink support that minimizes damage and improves heat dissipation during the laser lift-off process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sapphire substrate is used for growing Group III-V nitride-based semiconductor thin films, then high quality semiconductor films can be obtained, but the device suffers from poor thermal conductivity and cannot dissipate heat effectively
Solution Approach 1:
The device is segmented into multiple functional layers: the sapphire substrate maintains its role for high-quality film growth, while a separate heat-sink layer is introduced to handle thermal management. This segmentation allows each layer to optimize its specific function without compromise.
Solution Approach 2:
A heat-sink layer acts as an intermediary between the sapphire substrate and the external environment, mediating the heat transfer process. This intermediary layer absorbs excess heat generated during device operation and dissipates it effectively, preventing thermal accumulation while preserving the sapphire substrate's film growth advantages.
2Manufacturing precision
If a sapphire substrate is used, then the lattice constant mismatch causes mechanical stress and damage to the multi-layered light-emitting structure thin film
Solution Approach 1:
The device structure is segmented to separate the film growth function (sapphire substrate) from the mechanical stress management function (buffer layer and heat-sink layer). This segmentation allows the sapphire substrate to maintain its advantages for high-quality film growth while the buffer layer absorbs mechanical stress.
Solution Approach 2:
A buffer layer is introduced beforehand to cushion the mechanical stress generated by lattice constant mismatch between the sapphire substrate and the Group III-V nitride-based semiconductor thin films. This prior cushioning prevents film damage while preserving the sapphire substrate's film growth capabilities.
3Productivity
If the LED chip area is increased to improve performance, then the chip size becomes larger, but the sapphire substrate's poor thermal conductivity prevents effective heat dissipation from large area chips
Solution Approach 1:
A heat-sink layer serves as an intermediary thermal management system that scales with chip area. This layer provides proportional heat dissipation capacity for large-area chips, enabling high-performance LEDs to operate at increased power levels without thermal limitations.
Solution Approach 2:
The device employs a composite structure combining sapphire substrate (for film quality) with heat-sink materials (for thermal management). This composite approach allows the device to simultaneously achieve high performance through large chip area and effective heat dissipation.
4Device complexity
If a MESA structure is used on sapphire substrate, then both n-type and p-type ohmic contact electrodes are formed in the same growth direction, but this restricts further reduction of LED chip area
Solution Approach 1:
The electrode configuration is segmented into functionally independent n-type and p-type ohmic contact electrodes formed in the same growth direction. This segmentation maintains the MESA structure's advantages while allowing flexible chip size optimization for different application requirements.
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 reduces wafer warpage, micro-crack formation, and increases the production yield of LEDs by providing a stable and efficient heat dissipation mechanism, enhancing the reliability and performance of vertically-structured semiconductor light-emitting devices.
Implementation Method 1
thick metal film formed on an upper part of the sacrificial layer... absorb mechanical stress
Implementation Method 2
bonding layer formed on an upper part of the thick metal film and formed of a soldering or brazing alloy material
Implementation Method 3
bonding layer formed on an upper part of the thick metal film and formed of a soldering or brazing alloy material
Implementation Method 4
separating the sapphire substrate by a laser lift off process
Implementation Method 5
thick metal film... provide a stable heat-sink support... improves heat dissipation
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
The present invention is related to a light emitting device comprising a support (510); a second conductive layer (520) disposed on the support; a first conductive layer (530) disposed on the second conductive layer (520); an insulating layer (550) disposed on the second conductive layer (520); a second ohmic contact electrode (540) disposed on the first conductive layer (530); a light emitting structure (560) disposed on the second ohmic contact electrode (540), the light emitting structure (560) comprising an n-type group III-V nitride-based semiconductor layer, a group III-V nitride-based semiconductor active layer, and a p-type group III-V nitride-based semiconductor layer; a first ohmic contact electrode (570) disposed on the n-type group III-V nitride-based semiconductor layer; and a passivation layer (580) disposed on the insulating layer (550).