GaN Light Emitting Device Intermediate Layer
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Solution Overview
Problem
In semiconductor light emitting devices using III-V group nitride compound semiconductors, the piezoelectric effect caused by strain in InGaN and AlGaN layers leads to different strain directions, resulting in a piezoelectric field that increases positive hole density and reduces current density, degrading light emission characteristics.
Innovation Solution
Incorporating an intermediate layer between the electron barrier layer and the p-type light guide layer, which is lattice-matched to the GaN substrate and has a specific composition and thickness, to reduce band bending and limit lateral current spreading, thereby improving light emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Al composition ratio in the electron barrier layer is increased to restrict electron overflow, then the light emission efficiency is improved, but the crystallinity is degraded
Solution Approach 1:
The patent applies local quality by creating distinct layers with different Al composition ratios: the electron barrier layer has high Al composition (0.15-0.30) to restrict electron overflow, while the light guide layer has lower Al composition (0.05-0.20) to maintain good crystallinity and optical properties. This spatial differentiation of material composition allows each layer to optimize its function without compromising the other.
2Reliability
If the thickness of the electron barrier layer is increased to restrict electron overflow, then the light emission efficiency is improved, but the crystallinity is degraded
Solution Approach 1:
The patent optimizes the thickness of the electron barrier layer to a specific range (10-30 nm) to achieve sufficient electron restriction while maintaining crystallinity. The thinner barrier layer reduces strain accumulation that degrades crystallinity, while still providing adequate electron blocking function when combined with the appropriate Al composition ratio.
3Stability of the object's composition
If the Al composition ratio in the light guide layer is reduced to improve crystallinity, then the light emission characteristics are improved, but the electron barrier effect is weakened
Solution Approach 1:
The patent segments the electron barrier function from the light guide function by creating two separate layers: the electron barrier layer with high Al composition dedicated to electron restriction, and the light guide layer with lower Al composition dedicated to optical guidance and crystallinity. This functional segmentation allows each layer to optimize its primary role without compromise.
4Ease of manufacture
If InGaN and AlGaN layers are grown on GaN substrate, then the device structure is formed, but piezoelectric fields are generated that increase positive hole density and reduce current density
Solution Approach 1:
The patent introduces an intermediate layer between the InGaN active layer and the AlGaN electron barrier layer. This intermediate layer acts as a mediator that reduces the strength of the piezoelectric field generated by the strained InGaN/AlGaN interface, thereby reducing excessive positive hole density while maintaining the necessary device structure and electron barrier function.
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 intermediate layer reduces positive hole generation and current density reduction, enhancing light emission efficiency and reducing resistance, as demonstrated by improved threshold values and differential efficiency in the semiconductor light emitting device.
Implementation Method 1
the piezoelectric effect caused by strain in InGaN and AlGaN layers leads to different strain directions, resulting in a piezoelectric field that increases positive hole density and reduces current density
Data Source
AI summary
A semiconductor light emitting device has an active layer of a gallium nitride compound semiconductor material, a first semiconductor layer of Inx1Aly1Ga1−x1−y1N (0≦x1≦1, 0≦y1≦1), on a p-layer side of the active layer, and which is subjected to tensile strain, a second semiconductor layer of Inx2Aly2Ga1−x2−y2N, wherein (0≦x2≦1, 0 ≦y2≦1), and which has a bandgap energy smaller than the bandgap energy of the first semiconductor layer, and a third semiconductor layer between the first semiconductor layer and the second semiconductor layer, of Inx3Aly3Ga1−x3−y3N, wherein (0≦x3≦1, 0≦y3≦1), and which has a bandgap energy smaller than the bandgap energy of the first semiconductor layer and larger than the bandgap energy of the second semiconductor layer.