LED Substrate with Concavo-Convex Structures for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in maximizing light extraction efficiency due to total internal reflection and the geometry of the substrate, which limits the output of emitted light.
Innovation Solution
A light-emitting device manufacturing method involving a substrate with concavo-convex structures and an inclined surface is developed, where a semiconductor stack is grown epitaxially, and micro-structures are formed to reduce total internal reflection and enhance light extraction, including the use of a transparent conductive layer and electrodes for efficient light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat substrate is used, then the device structure is simple, but light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The substrate surface is modified with concavo-convex microstructures (protrusions and recesses) that create curved surfaces. These curved surfaces scatter light and reduce total internal reflection, thereby improving light extraction efficiency while maintaining manufacturing feasibility through standard semiconductor processing techniques
Solution Approach 2:
The substrate is designed with non-uniform local structures - specific regions contain concavo-convex microstructures while other areas maintain different characteristics. This local variation optimizes light extraction in specific zones without complicating the entire substrate structure, balancing manufacturing ease with performance improvement
2Device complexity
If vertical side walls are formed in the semiconductor stack, then the manufacturing process is simple, but light extraction efficiency is limited
Solution Approach 1:
The side walls of the semiconductor stack are formed with asymmetric angles rather than vertical geometry. The first and second side walls have different inclination angles relative to the substrate, creating asymmetric light extraction paths that improve overall light output by reducing directional dependence of total internal reflection
3Manufacturing precision
If the scribing region extends deep into the semiconductor stack, then separation precision is improved, but structural integrity is compromised
Solution Approach 1:
A relief structure is formed in the semiconductor stack prior to the scribing process. This pre-formed relief structure creates a designated weak point that guides the scribing process, allowing precise separation to occur at the intended location without requiring excessive scribing depth that would compromise the overall structural integrity of the semiconductor stack
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 method significantly improves light extraction efficiency by reducing total internal reflection and optimizing the substrate geometry, resulting in enhanced light output and performance of the light-emitting device.
Implementation Method 1
Conventional light-emitting diodes (LEDs) face challenges in maximizing light extraction efficiency due to total internal reflection and the geometry of the substrate
Implementation Method 2
The principle of the LED is to transform electrical energy to optical energy by applying electrical current to the LED and injecting electrons and holes to the active layer. The combination of electrons and holes in the active layer emits light accordingly
Data Source
AI summary
A manufacturing method of a light-emitting device includes steps of: providing a substrate with a top surface, wherein the top surface comprises a plurality of concavo-convex structures; forming a semiconductor stack on the top surface; forming a trench in the semiconductor stack to define a plurality of second semiconductor stacks and expose a first upper surface; forming a scribing region which extends from the first upper surface into the semiconductor stack and exposes a side surface of the semiconductor stack to define a plurality of first semiconductor stacks; removing a portion of the plurality of first semiconductor stacks and a portion of the concavo-convex structures trough the region to form a first side wall of each of the first semiconductor stack; and dividing the substrate along the region; wherein the first side wall and the top surface form an acute angle α between thereof, 30°≤α≤80°.