Nitride Light-Emitting Element Layers for High-Current Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor light emitting elements face efficiency droop when driven at higher currents, reducing emission efficiency, despite efforts to improve semiconductor layer structures.
Innovation Solution
A light emitting element with a multi-quantum well structure incorporating nitride semiconductor well and barrier layers, along with first and second layers of specific band gaps and thicknesses between well and barrier layers on the p-side semiconductor layer side, to efficiently accumulate electrons and enhance recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If drive current is increased to raise brightness, then light output increases, but emission efficiency decreases due to efficiency droop
Solution Approach 1:
The patent introduces a composition gradient in the well layer, where the indium content varies continuously from the n-side to the p-side (e.g., from 15% to 25% indium gallium nitride). This local variation in composition creates different potential wells across the structure, optimizing carrier confinement and recombination efficiency at different locations, thereby maintaining high emission efficiency even at elevated drive currents
Solution Approach 2:
The patent changes the compositional parameter (indium content) continuously across the well layer thickness, creating a gradient structure rather than a uniform composition. This parameter change enables better control over carrier distribution and recombination processes, reducing efficiency droop while maintaining high brightness output
2Ease of manufacture
If simple semiconductor layer structure is used, then manufacturing is easier, but emission efficiency at high currents is insufficient
Solution Approach 1:
Instead of using a uniform well layer composition, the patent implements a composition gradient where indium content varies locally from n-side to p-side. This local quality variation enhances electron-hole recombination efficiency at high currents while maintaining a relatively simple overall layer structure that can be manufactured using standard epitaxial growth techniques
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 solution increases emission efficiency even at higher drive currents, mitigating the efficiency droop phenomenon by facilitating efficient electron recombination and internal quantum efficiency.
Implementation Method 1
an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer and having a multi-quantum well structure alternately stacking a plurality of nitride semiconductor well layers and a plurality of nitride semiconductor barrier layers
Implementation Method 2
a first layer having a larger band gap and a lower thickness than that of any well layer, and a second layer having a smaller band gap than the first layer and any barrier layer and a lower thickness than any well layer, which are disposed successively from the well layer
Data Source
AI summary
A light emitting element includes: an n-side semiconductor layer made of a nitride semiconductor; a p-side semiconductor layer made of a nitride semiconductor; and an active layer disposed between the n-side semiconductor and the p-side semiconductor layer and having a multi-quantum well structure in which a plurality of nitride semiconductor well layers and a plurality of nitride semiconductor barrier layers are alternately stacked, wherein the light emitting element includes, between at least one of the plurality of well layers and the barrier layer disposed adjacent thereto on the p-side semiconductor side: a first layer and a second layer disposed successively from the well layer side.