Deep UV Nitride Semiconductor Light-Emitting Element with Phase-Aligned Reflected Light
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Solution Overview
Problem
Nitride semiconductor light-emitting elements, particularly those emitting deep ultraviolet light, face challenges in achieving sufficient light extraction efficiency due to the absorption properties of p-type GaN layers, which hinder the optimization of light extraction even when thicknesses of semiconductor and conductive layers are matched for phase alignment.
Innovation Solution
A nitride semiconductor light-emitting element is designed with a multi-quantum well layer producing deep ultraviolet light, a metal electrode for reflection, and a multi-stacked semiconductor layer with p-type AlGaN layers, along with an ITO contact electrode, where the refractive index difference is minimized to ensure phase alignment and enhanced light extraction by allowing reflected light to meet directly-emitted light in phase for improved output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type GaN layer is used as the second semiconductor layer, then the light-emitting element can achieve proper conductivity and carrier injection, but the deep ultraviolet light extraction efficiency is insufficient due to light absorption by the p-type GaN layer
Solution Approach 1:
The second semiconductor layer is divided into multiple thin p-type AlGaN sub-layers (first, second, and third p-type AlGaN layers) instead of using a single thick p-type GaN layer. This segmentation reduces the total thickness of light-absorbing material while maintaining the necessary p-type conductivity and carrier injection function, thereby improving deep ultraviolet light extraction efficiency
Solution Approach 2:
The invention changes the material composition from p-type GaN to p-type AlGaN with controlled aluminum composition ratios. By adjusting the aluminum content and layer thickness parameters, the refractive index and light absorption characteristics are optimized to reduce deep ultraviolet light absorption while maintaining proper electrical conductivity
2Loss of energy
If the thickness of the second semiconductor layer and conductive layer are independently set for phase matching, then light extraction efficiency can be improved, but the complexity of structure increases and deep ultraviolet light extraction remains insufficient due to material absorption properties
Solution Approach 1:
The invention simplifies the phase matching approach by changing the material parameters (using p-type AlGaN with specific aluminum composition ratios) rather than relying solely on precise thickness control. This material parameter change inherently provides better optical properties for deep ultraviolet light extraction while reducing the complexity of thickness optimization
3Loss of energy
If multiple layers are stacked to achieve phase alignment of directly-emitted and reflected light, then light extraction efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
By changing the material composition parameters (aluminum content in AlGaN layers), the invention achieves phase alignment and improves light extraction efficiency without requiring extremely precise thickness control. The material parameter adjustment provides a more tolerant manufacturing approach compared to strict thickness matching requirements
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 significantly enhances deep ultraviolet light extraction efficiency by ensuring that directly-emitted and reflected light amplify each other, leading to improved emission intensity and efficiency.
Implementation Method 1
a multi-quantum well layer (40) comprising AlGaN, and comprising a plurality of well layers (44) and producing light by combining carriers and emitting deep ultraviolet light
Implementation Method 2
a metal electrode part (920) comprising Al that is located above the multi-quantum well layer and reflects a first light that is a part of the light produced by the multi-quantum well layer
Implementation Method 3
the multi-stacked semiconductor layer (50) has and the ITO contact electrode part (922) have a film thickness that allows only the first light after traveling out and back within the multi-stacked semiconductor layer (50) and the ITO contact electrode part (922) via the reflection at the metal electrode part (920), and the second light to meet in the same phase
Data Source
AI summary
A nitride semiconductor light emitting element includes a multi-quantum well layer including AlGaN, and including a plurality of well layers and producing light by combining carriers and emitting deep ultraviolet light with a central wavelength of 250 nm to 350 nm, a metal electrode part including Al that is located above the multi-quantum well layer and reflects a first light that is a part of the light produced by the multi-quantum well layer and travels upward, a multi-stacked semiconductor layer that is located between the multi-quantum well layer and the metal electrode part, includes a plurality of p-type semiconductor layers including p-type AlGaN, and is configured in such a manner that the first light travels out and back therewithin via reflection at the metal electrode part until meeting a second light that is a part of the light produced by the multi-quantum well layer and travels downward, and an ITO contact electrode part provided between the metal electrode part and the multi-quantum well layer, and including an indium tin oxide, wherein a difference in refractive index between a p-type semiconductor layer and a layer adjacent thereto in the multi-stacked semiconductor layer is not more than 0.12, wherein the multi-stacked semiconductor layer and the ITO contact electrode part have a film thickness that allows only the first light after traveling out and back within the multi-stacked semiconductor layer and the ITO contact electrode part via the reflection at the metal electrode part, and the second light to meet in the same phase and exit from a lower side of the multi-quantum well layer.