LED Epitaxial Sublayer Structure for Stable Surface Roughening
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) with high aluminum content in their semiconductor layers are prone to over-roughening during surface treatment, leading to reduced light-emitting efficiency and stability due to faster etching rates and poorer processing stability, which affects the light extraction efficiency and luminous intensity.
Innovation Solution
A semiconductor epitaxial structure with a first semiconductor layer comprising sublayers of different aluminum content, where the first sublayer has a smaller aluminum content than the second sublayer, is used to control the etching rate and surface roughness, preventing over-roughening and improving light-emitting efficiency by creating a roughened surface with increased surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the aluminum content of the first semiconductor layer is increased to improve light extraction efficiency, then the etching rate increases and surface roughness decreases, but over-roughening occurs and processing stability deteriorates
Solution Approach 1:
The first semiconductor layer is divided into multiple sublayers with different aluminum contents. The sublayer closer to the active layer has lower aluminum content (slower etching rate) while the sublayer farther from the active layer has higher aluminum content (faster etching rate). This segmentation allows different regions to serve different functions: the lower aluminum content sublayer prevents over-roughening and maintains stability, while the higher aluminum content sublayer provides sufficient surface roughness for light extraction enhancement.
Solution Approach 2:
Different sublayers within the first semiconductor layer are assigned different aluminum contents to create local quality variations. The sublayer adjacent to the active layer has optimized aluminum content for stability and controlled roughness, while the sublayer farther away has higher aluminum content for enhanced light extraction. This local quality differentiation resolves the contradiction by allowing each region to optimize for its specific function.
2Illumination intensity
If the surface of the first semiconductor layer is roughened to improve light extraction efficiency, then luminous intensity increases, but surface roughness becomes unstable and over-roughening occurs
Solution Approach 1:
The first semiconductor layer is segmented into sublayers with graded aluminum contents, creating a gradient structure where etching rate varies through the thickness. This segmentation enables progressive roughening control during etching processes, preventing sudden over-roughening while achieving sufficient surface roughness for light extraction enhancement.
Solution Approach 2:
The aluminum content parameter is varied across different sublayers of the first semiconductor layer. By changing this compositional parameter spatially, the etching rate is controlled to achieve optimal surface roughness without over-roughening. The parameter change from lower to higher aluminum content across sublayers provides gradual roughness development during manufacturing.
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 approach enhances the light-emitting efficiency and luminous intensity of LEDs by maintaining stable surface roughness, preventing over-roughening, and improving current spreading uniformity, thereby increasing the reliability and performance of the diodes.
Implementation Method 1
surface roughening or changing a geometric structure of the LED is used to improve the external quantum efficiency (EQE), and to increase the luminous intensity and the light-emitting efficiency of the LED
Implementation Method 2
a portion of the light may be trapped inside the LED, reflect or refract back and forth due to total reflection, and eventually be absorbed by an electrode or the active layer of the LED
Implementation Method 3
The higher the aluminum content, the faster the roughening process, and the poorer the processing stability, and over-roughening may be resulted
Implementation Method 4
removing the growth substrate so as to expose the first surface of the first sublayer of the first semiconductor layer, and roughening the first surface of the first sublayer of the first semiconductor layer by etching
Data Source
AI summary
A light-emitting diode includes a semiconductor epitaxial structure that has a first surface and a second surface opposite to each other, and that includes a first semiconductor layer, a second semiconductor layer, an active layer, and a third semiconductor layer disposed in such order in a direction from the first surface to the second surface. The first semiconductor layer includes a first sublayer and a second sublayer. A surface of the first sublayer away from the second sublayer is the first surface. The first surface has a roughened surface. The second sublayer is closer to the second surface than the first sublayer. Each of the first sublayer and the second sublayer includes an aluminum-containing compound semiconductor material. An aluminum content of the first sublayer is smaller than that of the second sublayer. A method for manufacturing the light-emitting diode is also provided.