Resonant Cavity LED Sidewall Geometry for Light Extraction
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Solution Overview
Problem
Existing semiconductor technologies face challenges in achieving high efficiency of light extraction due to the complexity and instability of oxidation processes, which affect the control of electron and photon behavior, and result in stress at the oxide layer, reducing device reliability.
Innovation Solution
A resonant cavity light-emitting diode (RCLED) structure is developed, featuring a first reflective layer, a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked on a substrate. The second type semiconductor layer includes a first sidewall with a specific tangency point arrangement, where the second reflective layer covers the sidewall, enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an oxide layer with opening is used for lateral control of electron and photon, then light extraction can be achieved, but the oxidation process has high complexity and poor stability, making it difficult to accurately control oxidation depth
Solution Approach 1:
The patent removes the oxide layer completely and replaces it with a semiconductor layer having a specific sidewall structure. This extracts the problematic oxidation process from the device structure while maintaining the lateral control function through the engineered sidewall geometry with different tangent slopes at different heights.
Solution Approach 2:
The patent changes the control parameter from oxidation depth (which is difficult to control) to sidewall geometry parameters (tangent slopes at different heights). By controlling the sidewall shape through epitaxial growth rather than oxidation, the manufacturing precision is significantly improved while process complexity is reduced.
2Reliability
If an oxide layer is used for lateral control, then light extraction is enabled, but stress is generated at the opening due to thermal expansion coefficient difference between oxide and semiconductor, reducing device reliability
Solution Approach 1:
The patent extracts and removes the oxide layer that causes thermal expansion mismatch stress. By replacing it with a semiconductor layer that has compatible thermal properties, the source of stress is eliminated while the light extraction function is maintained through the sidewall structure design.
Solution Approach 2:
The patent uses a semiconductor layer instead of an oxide layer, creating material homogeneity between the control layer and the active region. This eliminates the thermal expansion coefficient difference and prevents stress generation at interfaces, improving device reliability.
3Productivity
If conventional light extraction methods are used, then light can be emitted, but light extraction efficiency is low and photons escape slowly
Solution Approach 1:
The patent applies different sidewall slopes at different heights of the semiconductor layer. The first sidewall portion has a first tangent slope and the second sidewall portion has a second tangent slope, creating local variations in light reflection and extraction characteristics. This local quality differentiation optimizes photon escape pathways and increases overall light extraction efficiency.
Solution Approach 2:
The patent uses curved sidewall surfaces with specific tangent slopes instead of straight vertical walls. The curved geometry with controlled tangent slopes at different heights facilitates directional light extraction and accelerates photon escape by optimizing reflection angles within the resonant cavity.
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 RCLED structure improves light extraction efficiency by directing photons to be directionally emitted, accelerating their escape and enhancing spectral purity, thus overcoming the limitations of existing technologies.
Implementation Method 1
Resonant cavity light-emitting diode
Implementation Method 2
first reflective layer, second reflective layer
Data Source
AI summary
A resonant cavity light-emitting diodes includes a first reflective layer, a first type semiconductor layer, an active layer and a second type semiconductor layer sequentially which are stacked on a first substrate, and a second reflective layer covering a first sidewall of the second type semiconductor layer. An upper surface on a side of the second type semiconductor layer away from the first substrate serves as a light outlet. The first reflective layer and the second reflective layer form a resonant cavity. Light is capable to be reflected for many times in the resonant cavity. The first sidewall includes a lower tangency point and an upper tangency point which are arranged from bottom to top, and a tangent slope at the upper tangency point is larger than a tangent slope at the lower tangency point.