UV Light Emitting Element Barrier Structure for Higher Recombination
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Solution Overview
Problem
Current ultraviolet light emitting elements with multiple quantum well structures face challenges in achieving high output due to lattice relaxation and surface roughness issues, which reduce electron-hole recombination probability.
Innovation Solution
The use of a specific structure comprising an n-side nitride semiconductor layer, an active layer with alternating AlGaN and AlInGaN barrier layers, and a p-side nitride semiconductor layer, where the barrier layers have a band gap energy gradient to enhance electron confinement and recombination probability, is introduced. This structure includes a first barrier layer with Al and Ga, and a second barrier layer with Al, Ga, and In, having a smaller band gap energy than the first barrier layer, to improve crystallinity and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a multiple quantum well structure is used in ultraviolet light emitting elements, then the emission capability is improved, but lattice relaxation and surface roughness occur which reduce electron-hole recombination probability
Solution Approach 1:
The patent introduces a graded band gap energy structure by varying the composition of barrier layers (AlGaN and AlInGaN with different ratios) to create a gradual transition in band gap energy. This parameter change allows for better lattice matching across interfaces, reducing lattice relaxation and maintaining high electron-hole recombination probability while preserving the multiple quantum well emission capability.
Solution Approach 2:
The patent employs composite barrier layer structures combining AlGaN and AlInGaN materials with different compositions. The first barrier layer (AlGaN) and second barrier layer (AlInGaN) form a composite structure that leverages the advantages of both materials - AlGaN provides high band gap for ultraviolet emission while AlInGaN with lower band gap reduces lattice mismatch, together solving the contradiction between emission output and recombination efficiency.
2Illumination intensity
If barrier layers with large band gap energy difference are used to enhance electron confinement, then emission output is improved, but lattice relaxation increases
Solution Approach 1:
The patent implements a graded band gap structure where the band gap energy changes gradually across the barrier layers. The first barrier layer (AlGaN) has higher band gap energy for electron confinement, while the second barrier layer (AlInGaN) has lower band gap energy to reduce lattice mismatch. This gradual parameter transition maintains electron confinement effectiveness while minimizing lattice relaxation.
Solution Approach 2:
Different regions of the barrier structure are assigned different material compositions and band gap energies tailored to local requirements. The first barrier layer (AlGaN) is positioned where strong electron confinement is needed, while the second barrier layer (AlInGaN) is positioned at interfaces where lattice matching is critical. This local optimization resolves the contradiction between electron confinement and lattice stability.
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 increases the electron-hole recombination probability and emission output of the ultraviolet light emitting element, surpassing the performance of elements without the first barrier layer, while maintaining good crystallinity and reducing lattice relaxation.
Implementation Method 1
the barrier layers have a band gap energy gradient to enhance electron confinement and recombination probability
Implementation Method 2
enhance electron confinement and recombination probability
Implementation Method 3
an active layer emitted ultraviolet light disposed on the n-side nitride semiconductor layer
Data Source
AI summary
A light emitting element includes an n-side nitride semiconductor layer; an active layer disposed on the n-side nitride semiconductor layer and including a plurality of nitride semiconductor well layers and a plurality of nitride semiconductor barrier layers, the active layer being configured to emit ultraviolet light; and a p-side nitride semiconductor layer disposed on the active layer. At least one of the plurality of barrier layers including, successively from the n-side nitride semiconductor layer side, a first barrier layer containing Al and Ga, and a second barrier layer disposed in contact with the first barrier layer, containing Al, Ga, and In, and having a smaller band gap energy than the first barrier layer. At least one of the plurality of well layers is disposed in contact with a second barrier layer and has a smaller band gap energy than the second barrier layer.