Nitride Semiconductor Light-Emitting Element Graded Layer
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Solution Overview
Problem
The existing nitride semiconductor light-emitting elements experience a decrease in emission output due to the occurrence of a notch in the band structure and electric field generation at the interface between the n-type cladding layer and the barrier layer, caused by a sharp change in Al composition ratio and piezoelectric effects.
Innovation Solution
Incorporating a graded layer with an Al composition ratio that increases at a predetermined rate between the n-type cladding layer and the barrier layer, preventing a notch in the band structure and reducing the electric field generated by the piezoelectric effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the Al composition ratio changes sharply at the interface between the n-type cladding layer and the first barrier layer, then the multiple quantum well structure can be formed with distinct barriers, but a notch in the band structure occurs and electron flow is interrupted
Solution Approach 1:
The patent applies parameter changes by introducing a graded layer where the Al composition ratio gradually transitions from the n-type cladding layer to the first barrier layer. This gradual parameter change prevents the sharp interface that causes band structure notches, while still maintaining the multiple quantum well structure's functional integrity and electron flow continuity.
Solution Approach 2:
The graded layer acts as an intermediary between the n-type cladding layer and the first barrier layer. This intermediate layer with gradually changing composition mediates the transition, avoiding the direct sharp interface that would create harmful band structure notches and electron flow interruption.
2Manufacturing precision
If the Al composition ratio increases sharply at the interface, then the barrier function is clearly defined, but an electric field is generated due to the piezoelectric effect that interrupts electron flow
Solution Approach 1:
The patent uses parameter changes by implementing a graded composition profile in the graded layer. This gradual parameter transition reduces the strain gradient at the interface, thereby minimizing the piezoelectric effect and the resulting harmful electric field that would interrupt electron flow.
3Reliability
If a graded layer with gradual Al composition ratio increase is introduced, then band structure notches are prevented and electron flow is maintained, but the device structure becomes more complex
Solution Approach 1:
The patent resolves the complexity issue by implementing the graded layer with a controlled and systematic parameter change in Al composition ratio. This approach maintains reliability and prevents band structure notches while keeping the structural complexity manageable through a well-defined gradient profile rather than multiple discrete layers.
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 enhances the emission output of nitride semiconductor light-emitting elements by preventing band structure notches and reducing electric fields, leading to improved light emission efficiency.
Implementation Method 1
an electric field is generated at such an interface due to the piezoelectric effect
Data Source
AI summary
A nitride semiconductor light-emitting element includes an n-type cladding layer including n-type AlGaN having a first Al composition ratio, a barrier layer including AlGaN that is located on the n-type cladding layer side in a multiple quantum well layer and has a second Al composition ratio greater than the first Al composition ratio, and a graded layer that is located between the n-type cladding layer and the barrier layer and has a third Al composition ratio that is between the first Al composition ratio and the second Al composition ratio, wherein the third Al composition ratio of the graded layer increases at a predetermined increase rate from the first Al composition ratio toward the second Al composition ratio.