LED Chip Wavelength Stability via Segmented Quantum Wells
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Solution Overview
Problem
Optoelectronic semiconductor chips experience a shift in emission wavelength and reduced brightness due to temperature-induced decreases in bandgap, leading to altered perceived color and reduced visually perceived brightness, especially at longer wavelengths.
Innovation Solution
A multiple quantum well structure is implemented, comprising alternating quantum well and barrier layers with varying bandgaps, where the second region has a larger bandgap barrier layer impeding hole mobility, concentrating holes and enhancing radiative recombination at low temperatures, and as temperature increases, hole mobility allows recombination in both regions, stabilizing the emission spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional LED structure is used, then the device is simple to manufacture, but the emission wavelength shifts significantly with temperature increase
Solution Approach 1:
The active layer is segmented into multiple quantum well regions with different bandgap energies. Each quantum well region contains alternating layers of different semiconductor materials creating discrete energy levels. This segmentation allows different regions to contribute to emission at different wavelengths, enabling temperature compensation through the combined spectral output.
Solution Approach 2:
Different quantum well regions are designed with locally optimized properties - specific bandgap energies and material compositions tailored to their functional roles. The first quantum well region has properties optimized for one emission characteristic while the second region has properties optimized for another, allowing each local region to contribute differently to the overall temperature stability.
2Illumination intensity
If the bandgap is decreased to increase brightness, then the visually perceived brightness improves, but the emission wavelength increases and color perception deteriorates
Solution Approach 1:
The LED employs composite semiconductor materials in the quantum well structure, combining different III-V compound semiconductors with varying bandgap energies. This composite material approach enables the structure to emit across a broader spectral range, compensating for wavelength shifts while maintaining high visual brightness through optimized material composition and layer design.
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 emission spectrum remains relatively stable with minimal change in dominant wavelength and perceived brightness, even across temperature variations from 25°C to 85°C, effectively counteracting the temperature-dependent bandgap decrease.
Implementation Method 1
the at least one second barrier layer has a bandgap EB2 which is larger than the bandgap EB1 of the first barrier layers... movement of holes in the multiple quantum well structure is more difficult in the vicinity of the p-type semiconductor region
Implementation Method 2
there is a greater probability of radiative recombinations of electrons and holes taking place in the second region of the quantum well structure
Implementation Method 3
radiation-emitting optoelectronic semiconductor chip
Implementation Method 4
The bandgap of semiconductor materials generally decreases with rising temperature. For radiation-emitting optoelectronic semiconductor chips such as LEDs or semiconductor lasers, for example, this can result in the wavelength of the emitted radiation increasing with rising operating temperature
Data Source
AI summary
An optoelectronic semiconductor chip is disclosed. In an embodiment the optoelectronic semiconductor chip includes a p-type semiconductor region, an n-type semiconductor region, and an active layer arranged between the p-type semiconductor region and the n-type semiconductor region. The active layer is designed as a multiple quantum well structure, wherein the multiple quantum well structure has a first region of alternating first quantum well layers and first barrier layers and a second region having at least one second quantum well layer and at least one second barrier layer. The at least one second quantum well layer has an electronic band gap (EQW2) that is less than the electronic band gap (EQW1) of the first quantum well layers, and the at least one second barrier layer has an electronic band gap (EB2) that is greater than the electronic band gap (EB1) of the first barrier layers.