Multi-Quantum Well LED Structure for Mixed White Light Emission
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Solution Overview
Problem
Existing nitride semiconductor light emitting diodes primarily emit monochromatic light, making it difficult to produce mixed color light sources, especially white light with high color rendering index, using conventional methods.
Innovation Solution
A light emitting device with a first semiconductor stacked structure emitting multi-color light and a red light source, utilizing a multi-quantum well structure and a phosphor to convert light into red light, combined with a second semiconductor stacked structure to generate blue and yellow light, enhancing color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light emitting diode uses a heterojunction structure with a quantum well structure to emit monochromatic light, then internal quantum efficiency is increased and light absorption losses are reduced, but it becomes difficult to produce mixed color light sources such as white light
Solution Approach 1:
The active layer is divided into multiple quantum well structures with different compositions, where each quantum well emits light at a different wavelength. This segmentation allows a single LED to produce multiple wavelengths simultaneously, resolving the contradiction between maintaining high efficiency and achieving mixed color emission.
Solution Approach 2:
The patent uses composite quantum well structures with varying material compositions (different Al content in AlGaN layers) within the same active layer. This composite approach enables different regions to emit different wavelengths while maintaining the overall heterojunction structure's efficiency, thus achieving both energy efficiency and color versatility.
2Adaptability or versatility
If multiple light emitting diodes emitting different monochromatic lights are used together to implement mixed color light, then the desired spectrum is achieved, but device complexity increases
Solution Approach 1:
The patent merges multiple quantum well structures into a single active layer, which is then integrated into one light emitting diode device. This combining approach achieves mixed color emission from a single device rather than requiring multiple separate LEDs, thus reducing device complexity while maintaining color versatility.
Solution Approach 2:
The single light emitting diode with multi-quantum well structure performs multiple functions simultaneously - emitting multiple wavelengths of light from one device. This multi-functionality eliminates the need for multiple specialized LEDs, simplifying the overall system while achieving the desired mixed color output.
3Adaptability or versatility
If multiple phosphors are used to convert the wavelength of light emitted from light emitting diodes to achieve mixed color light, then the desired spectrum is achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces the external phosphor conversion approach with an internal quantum well emission approach. Instead of using one LED plus multiple phosphors, the design uses multiple quantum wells within a single LED to directly emit different wavelengths. This substitution simplifies manufacturing by eliminating the need for complex phosphor coating and alignment processes.
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
The device achieves mixed color light emission, including white light with improved color rendering index and correlated color temperature, surpassing conventional methods that rely on multiple diodes or phosphors.
Implementation Method 1
the active layer has a multi-quantum well structure including a plurality of barrier layers and a plurality of well layers stacked one over another, and the active layer is configured to emit multi-color light
Implementation Method 2
The red light source may include a phosphor configured to convert a wavelength of light emitted from the first semiconductor stacked structure into red light
Data Source
AI summary
A light emitting device including a first semiconductor stacked structure configured to emit multi-color light, and a red light source configured to emit red light, in which the first semiconductor stacked structure includes a first conductivity-type nitride semiconductor layer, an active layer disposed on the first conductivity-type nitride semiconductor layer, and a second conductivity-type nitride semiconductor layer disposed on the active layer, the active layer has a multi-quantum well structure including a plurality of barrier layers and a plurality of well layers stacked one over another, and the active layer is configured to emit multi-color light.