Single-Chip Multi-Band LED With Current-Tunable White Emission
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) using nitride semiconductors emit monochromatic light, which limits their ability to produce mixed color light, such as white light, requiring multiple LEDs or phosphors, complicating manufacturing and increasing costs and inefficiencies.
Innovation Solution
A novel light emitting diode structure with a nitride semiconductor layer, active layer, and p-type nitride semiconductor layer that emits light varying from yellow to white based on driving current, utilizing a V-pit generation layer and a p-type AlxGa1-xN layer to achieve multi-band spectrum emission at a single chip level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single light emitting diode emits monochromatic light, then the internal quantum efficiency is increased and light absorption loss is reduced, but the ability to produce mixed color light such as white light is limited
Solution Approach 1:
The active layer is divided into multiple quantum well structures with different compositions (InGaN wells with varying In content), each emitting at different wavelengths. This segmentation allows a single LED chip to generate multiple wavelength bands simultaneously, enabling white light emission without compromising internal quantum efficiency.
Solution Approach 2:
Different regions of the active layer are designed with locally optimized compositions - some quantum wells have higher In content for yellow-green emission while others have lower In content for blue emission. This local quality variation enables spectral diversity within a single chip while maintaining efficient light generation in each region.
2Adaptability or versatility
If multiple light emitting diodes are used to produce white light, then mixed color light can be achieved, but the manufacturing process becomes complicated
Solution Approach 1:
Multiple quantum well structures with different emission wavelengths are merged into a single active layer within one LED chip. This integration combines the functions of what would traditionally require separate LEDs, simplifying the manufacturing process by producing white light emitters through a single epitaxial growth process rather than assembling multiple chips.
Solution Approach 2:
The single LED chip structure is designed to perform multiple functions - generating blue light, yellow-green light, and their combination for white light emission - all within one device. This multi-functionality eliminates the need for separate LEDs or phosphor conversion layers, reducing manufacturing steps and improving reliability.
3Adaptability or versatility
If phosphors are used to convert wavelength, then white light can be produced, but cost increases and efficiency decreases due to Stoke's shift
Solution Approach 1:
The phosphor conversion layer is extracted and replaced with direct blue LED emission combined with yellow-green emission from specific quantum wells. This eliminates the phosphor material and its associated Stoke's shift losses, achieving white light through direct electroluminescence from multiple quantum well regions with different compositions.
4Adaptability or versatility
If phosphors are coated on the light emitting diode, then wavelength conversion is achieved, but manufacturing drawbacks occur including yellowing of the carrier
Solution Approach 1:
The phosphor coating process and carrier substrate are extracted from the structure. Instead, the invention uses a direct multi-quantum well active layer that generates the required spectrum through controlled epitaxial growth, eliminating the phosphor coating step and the associated reliability issues of carrier yellowing and delamination.
5Device complexity
If a single chip emits monochromatic light, then the structure is simple, but adjustable color temperature and luminance cannot be achieved
Solution Approach 1:
The LED structure incorporates multiple quantum well regions with different compositions that can be dynamically activated at different current levels. By adjusting the driving current, different quantum wells are selectively excited, enabling dynamic adjustment of color temperature and luminance while maintaining a relatively simple single-chip structure.
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
Enables the production of white light without the need for multiple LEDs or phosphors, reducing manufacturing complexity and costs, while providing adjustable color temperature and luminance through current control.
Implementation Method 1
an active layer located on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer located on the active layer
Data Source
AI summary
A lighting apparatus includes a light emitting diode, in which the light emitting diode includes an n-type nitride semiconductor layer, an active layer located on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer located on the active layer. The light emitting diode emits light that varies from yellow light to white light depending on a driving current.