Nitride LED Layer Structure for Low-Pit Conductive Mirrors
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Solution Overview
Problem
Existing nitride semiconductor multilayer films suffer from high defect densities, particularly threading dislocations, when forming a multilayer film reflecting mirror structure with conductivity, which affects the conductivity and longevity of the nitride semiconductor light emitting elements.
Innovation Solution
A nitride semiconductor light emitting element with a specific layer structure comprising a first layer containing Al and In, a cap layer containing Ga, and a second layer containing Al and Ga, where the molar fraction of AlN at the interface of the second layer is between 0.36 and 0.44, and a production method involving controlled temperature changes during crystal growth to enhance surface flattening and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an n-AlGaInN composition gradient layer is formed at the same temperature as the n-AlInN layer to maintain conductivity, then good conductivity is achieved, but many pits are generated on the surface
Solution Approach 1:
The patent changes the growth temperature parameter during the formation of the second layer. Specifically, the second layer containing Al and Ga is formed at a higher temperature than the first layer, which allows for better surface quality and reduced pit formation while maintaining the desired conductivity through controlled composition gradients
2Manufacturing precision
If a GaN cap layer of 0.3 nm is formed and temperature increasing step is performed to reduce pits, then surface quality improves, but the effect of reducing threading dislocation is diminished when n-AlGaInN composition gradient layer is formed at same temperature
Solution Approach 1:
The patent forms a cap layer free of In before forming the composition gradient layer. This preliminary action of creating a clean GaN cap layer surface before subsequent growth steps helps prevent threading dislocation propagation while maintaining surface quality
Solution Approach 2:
The second layer containing Al and Ga acts as an intermediary layer between the first layer (n-AlInN) and the cap layer. This intermediate layer with controlled composition gradient mediates the transition, reducing both surface pits and threading dislocations by providing a gradual compositional transition zone
3Reliability
If Si is added to n-AlGaInN composition gradient layer to enhance conductivity, then conductivity improves, but pit density increases
Solution Approach 1:
The patent applies local quality by adding Si specifically to the second layer containing Al and Ga, rather than uniformly throughout the entire structure. This localized doping approach enhances conductivity in the critical region while minimizing the impact on surface quality and pit formation
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 reduces energy barriers, improves electron exchange, and results in a nitride semiconductor light emitting element with low pit density, high conductivity, and extended lifespan.
Implementation Method 1
a temperature at which the second layer is crystal-grown in the second layer stacking step is equal to or higher than a temperature at which the third layer is crystal-grown in the third layer stacking step
Data Source
AI summary
Provided are a nitride semiconductor light emitting element of good quality and a method for producing a nitride semiconductor light emitting element of good quality. A nitride semiconductor light emitting element (1) includes an n-AlInN layer (12) containing Al and In in its composition, a GaN cap layer (13) stacked on a surface of the n-AlInN layer (12) and containing Ga in its composition, and an n-AlGaN composition gradient layer (14) stacked on a surface of the GaN cap layer (13) and containing Al and Ga in its composition. A molar fraction of AlN at an interface of the n-AlGaN composition gradient layer (14) stacked on the surface of the GaN cap layer (13) is 0.36 or more and 0.44 or less.