UV Semiconductor Light Emitting Devices with Trench Insulators
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Solution Overview
Problem
Ultraviolet nitride semiconductor LEDs suffer from low external quantum efficiency and light extraction efficiency due to Auger recombination and high refractive indices, making commercialization challenging, especially for short-wavelength UV LEDs.
Innovation Solution
The design includes a semiconductor stack with trenches filled with an insulating material of lower refractive index than the active layer, optimizing the sidewall angle and refraction angles to redirect light laterally and improve extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If nitride semiconductor LEDs are configured to emit short-wavelength ultraviolet light, then the UV light source capability is improved, but the light extraction efficiency deteriorates to extremely low levels (2-3%)
Solution Approach 1:
The patent divides the semiconductor structure into multiple quantum well layers with different Al compositions, creating distinct emission regions. The first AlGaN layer has higher Al composition for shorter wavelength UV emission, while the second AlGaN layer has lower Al composition for longer wavelength UV emission, allowing segmented wavelength control and improved light extraction
Solution Approach 2:
The patent applies different Al compositions locally within the semiconductor structure. The first AlGaN layer uses higher Al composition (x1) for short-wavelength UV emission, while the second AlGaN layer uses lower Al composition (x2) for long-wavelength UV emission, optimizing local emission characteristics and overall light extraction efficiency
2Reliability
If the semiconductor material has high refractive index, then the material can support UV emission, but the light extraction efficiency deteriorates due to lateral light propagation and reabsorption
Solution Approach 1:
The patent transitions from a single-layer planar structure to a multi-layer vertical structure with different Al compositions. This dimensional organization allows light to be extracted through multiple interfaces and wavelengths, converting the problem of lateral light propagation into a vertical extraction mechanism that reduces reabsorption losses
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 significantly enhances luminous efficiency by changing the path of light traveling in the lateral direction, reducing reabsorption and increasing the probability of light extraction, thereby improving overall light emission efficiency.
Implementation Method 1
a filling insulator filling the at least one trench such that the filling insulator extends at least through the active layer in the at least one trench, the filling insulator including an insulating material, the insulating material having a lower refractive index than the active layer
Data Source
AI summary
An ultraviolet semiconductor light emitting device includes a semiconductor stack, a trench, a filling insulator, and first and second electrodes. The semiconductor stack includes first and second conductivity-type semiconductor layers and an active layer therebetween that includes an AlGaN semiconductor material. The trench extends through the second conductivity-type semiconductor layer and the active layer to the first conductivity-type semiconductor layer and has a first width. The filling insulator fills the trench such that the filling insulator extends at least through the active layer in the trench and includes of an insulating material having a particular refractive index. The first electrode is connected to the first conductivity-type semiconductor layer, and the second electrode is connected to the second conductivity-type semiconductor layer.