Nitride Semiconductor Light Emitting Device Thermal Management
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Solution Overview
Problem
Nitride semiconductor light emitting devices face challenges in increasing light output due to carrier overflow caused by piezoelectric fields induced by lattice mismatch strain, which leads to reduced effective barrier height and increased heat generation, resulting in optical saturation.
Innovation Solution
A nitride semiconductor light emitting device configuration is implemented, where the nitride semiconductor light emitting element is mounted on a submount with a lower thermal expansion coefficient and higher thermal conductivity than the element itself, effectively reducing carrier overflow and increasing light output by managing thermal expansion and strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the amount of applied current is increased to increase light output, then light output is improved, but heat generation increases causing carrier overflow and optical saturation
Solution Approach 1:
A heat dissipation layer is introduced as an intermediary between the nitride semiconductor light emitting element and the submount. This layer has higher thermal conductivity than both the light emitting element and the submount, serving as a thermal bridge to efficiently conduct heat away from the active region, thereby reducing carrier overflow and maintaining high light output without optical saturation
Solution Approach 2:
The thermal conductivity parameter of the mounting structure is optimized by selecting materials and configurations that maximize heat removal. The heat dissipation layer is specifically designed with superior thermal conductivity properties to change the thermal parameters of the overall system, enabling higher current operation without temperature-induced performance degradation
2Reliability
If a layer with large energy band gap is inserted near the active layer to reduce carrier overflow, then carrier overflow is reduced, but lattice mismatch strain increases causing piezoelectric fields that reduce effective barrier height
Solution Approach 1:
The heat dissipation layer serves as a mechanical intermediary that can accommodate lattice mismatch strain without transmitting excessive stress to the active region. By providing a compliant thermal management interface, it allows the use of high Al-content AlGaN layers for carrier confinement while managing the associated piezoelectric effects through thermal and mechanical decoupling
Solution Approach 2:
The patent applies different material properties to different regions: the heat dissipation layer is positioned specifically between the light emitting element and submount to provide localized thermal management, while allowing the active region to maintain its carrier confinement structure. This local optimization enables carrier overflow suppression without propagating lattice mismatch strain throughout the entire device
3Temperature
If high thermal conductivity material is used for the submount to reduce heat generation, then heat dissipation is improved, but thermal expansion mismatch may cause additional strain
Solution Approach 1:
The thermal conductivity parameter of the heat dissipation layer is optimized to be higher than both the light emitting element and the submount, creating a thermal gradient that efficiently conducts heat away from the active region. This parameter optimization enables effective heat management while the layered structure accommodates thermal expansion differences
Solution Approach 2:
The mounting structure employs a composite configuration with the heat dissipation layer positioned between the light emitting element and the submount. This composite structure combines materials with different thermal and mechanical properties to achieve both superior heat dissipation and strain management, allowing the system to benefit from high thermal conductivity while mitigating thermal expansion mismatch through the intermediate layer
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 configuration allows for increased light output while reducing carrier overflow and heat-related issues, enhancing the performance of nitride semiconductor light emitting devices without inducing plastic deformation, thus improving their reliability and efficiency.
Implementation Method 1
mounted on a submount with a lower thermal expansion coefficient and higher thermal conductivity than the element itself, effectively reducing carrier overflow and increasing light output by managing thermal expansion and strain
Implementation Method 2
mounted on a submount with a lower thermal expansion coefficient and higher thermal conductivity than the element itself, effectively reducing carrier overflow and increasing light output by managing thermal expansion and strain
Implementation Method 3
A light emitting element such as a nitride semiconductor light emitting element emits light through recombination of electrons and holes (electron-hole pairs) injected into an active layer formed by, for example, a quantum well of the light emitting device
Implementation Method 4
carrier overflow caused by piezoelectric fields induced by lattice mismatch strain, which leads to reduced effective barrier height
Data Source
AI summary
A semiconductor light emitting device includes: a nitride semiconductor light emitting element including a nitride semiconductor substrate having a polar or semipolar surface and a nitride semiconductor multilayer film stacked on the polar or semipolar surface; and a mounting section to which the element is mounted. The nitride semiconductor multilayer film includes an electron block layer. The electron block layer has a smaller lattice constant than the nitride semiconductor substrate. The mounting section includes at least a first mounting section base. The first mounting section base is located close to the nitride semiconductor light emitting element. The first mounting section base has a lower thermal expansion coefficient than the nitride semiconductor multilayer film. The first mounting section base has a lower thermal conductivity than the nitride semiconductor multilayer film.