Nitride Light-Emitting Layer Structure for Mg Diffusion Control
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Solution Overview
Problem
In nitride semiconductor light-emitting elements that emit blue light, the electrical resistance is higher for short-wavelength elements, and the activation rate of Mg in the p-type AlGaN layer reduces with increasing Al composition, leading to reduced hole injection efficiency and increased non-radiative recombination centers due to Mg incorporation into the light-emitting layer through thermal diffusion.
Innovation Solution
A nitride semiconductor light-emitting element configuration that includes an n-side semiconductor layer, light-emitting layers, Al barrier layers, a p-side guiding layer with a lower Al composition ratio, an electron blocking layer with a higher Al composition ratio, and a p-side semiconductor layer, which prevents Mg incorporation into the light-emitting layer and enhances hole injection efficiency by using a second barrier layer with a larger Al composition ratio and thinner thickness to reduce electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Mg is added to the proximity of the light-emitting layer to enhance hole injection efficiency, then hole injection efficiency is improved, but Mg is incorporated into the light-emitting layer due to thermal diffusion, increasing non-radiative recombination centers and reducing light-emitting efficiency
Solution Approach 1:
The patent introduces a p-type AlGaN layer as an intermediary between the p-type contact layer and the light-emitting layer. This intermediary layer has lower Al composition (and thus lower electrical resistance) compared to the contact layer, allowing it to serve as a buffer that prevents Mg atoms from diffusing into the light-emitting layer while still enabling effective hole injection. The intermediary layer thus mediates between the conflicting requirements of high hole injection efficiency and prevention of Mg contamination.
Solution Approach 2:
The patent applies local quality by creating a gradient in Al composition across different layers. The p-type contact layer has high Al composition for low electrical resistance, the p-type AlGaN layer has intermediate Al composition to balance resistance and Mg diffusion prevention, and the light-emitting layer has low Al composition to maintain high light-emitting efficiency. Each layer is optimized locally for its specific function while contributing to the overall system performance.
2Reliability
If Al composition ratio in p-type AlGaN layer is increased to reduce electrical resistance, then electrical resistance is reduced, but activation rate of Mg decreases, reducing hole injection efficiency
Solution Approach 1:
The patent segments the p-type semiconductor layer into two distinct layers with different Al composition ratios: a p-type contact layer with high Al composition for low electrical resistance, and a p-type AlGaN layer with lower Al composition for high Mg activation rate and hole injection efficiency. This segmentation allows each layer to be optimized for its primary function without compromise.
Solution Approach 2:
Different regions of the p-type semiconductor structure are assigned different Al composition ratios tailored to their specific functions. The contact layer near the electrode is optimized for electrical conductivity with high Al content, while the layer adjacent to the light-emitting layer is optimized for hole injection with lower Al content and higher Mg activation rate.
3Illumination intensity
If AlGaN-based material is used for light guiding layer in short-wavelength element, then band-gap energy is increased for shorter wavelength emission, but electrical resistance becomes larger compared to InGaN-based elements
Solution Approach 1:
The patent optimizes the Al composition ratio in the light guiding layer to achieve the appropriate band-gap energy for short-wavelength emission while controlling electrical resistance. By carefully selecting the Al composition (not too high to maintain acceptable resistance, not too low to achieve sufficient band-gap), the light guiding layer is locally optimized for both optical and electrical performance.
Solution Approach 2:
The patent adjusts the Al composition ratio parameter in the AlGaN-based light guiding layer to achieve the desired band-gap energy for short-wavelength emission. By changing this compositional parameter, the band-gap energy is increased to enable emission at wavelengths shorter than blue light, while the electrical resistance is managed through optimized composition selection.
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 prevents Mg incorporation into the light-emitting layer, thereby enhancing hole injection efficiency and reducing electrical resistance, leading to improved light-emitting efficiency and output in nitride semiconductor light-emitting elements.
Implementation Method 1
Mg is incorporated into the light-emitting layer due to thermal diffusion
Implementation Method 2
an AlGaN-based material having band-gap energy larger than the band-gap energy of InGaN is used for a light guiding layer
Data Source
AI summary
A nitride semiconductor light-emitting element includes: an n-side semiconductor layer; one or more light-emitting layers disposed above the n-side semiconductor layer; a first barrier layer disposed above the one or more light-emitting layers and including Al; a second barrier layer disposed above the first barrier layer and including Al; a p-side guiding layer disposed above the second barrier layer and having an Al composition ratio smaller than an Al composition ratio of the second barrier layer; an electron blocking layer disposed above the p-side guiding layer, including Mg, and having an Al composition ratio larger than the Al composition ratio of the second barrier layer; and a p-side semiconductor layer disposed above the electron blocking layer.