LED DBR Structure With Roughened Interfaces for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in enhancing external quantum efficiency due to total reflection and absorption of light within the distributed Bragg reflector (DBR) structure, leading to reduced luminous efficiency and increased risk of backside chipping during manufacturing.
Innovation Solution
The proposed solution involves a light-emitting diode design that incorporates a DBR structure with light-transmitting layers having different refractive indices and roughened interfaces, which reduces total reflection and enhances light transmission, thereby improving luminous efficiency and adhesion between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional DBR structure with smooth interfaces is used, then the structural integrity is maintained, but total reflection occurs causing reduced light transmission and luminous efficiency
Solution Approach 1:
The patent applies parameter changes by modifying the interface morphology from smooth to roughened, and altering the refractive index distribution in the DBR structure. This transforms the optical properties to reduce total reflection while maintaining structural integrity, directly resolving the contradiction between ease of manufacture and luminous efficiency
Solution Approach 2:
The patent implements local quality by creating roughened interfaces at specific locations within the DBR structure where light reflection occurs, while keeping other structural elements intact. This localized modification optimizes light transmission without compromising overall structural integrity
2Reliability
If light undergoes multiple total reflections in the DBR structure, then the light is contained within the structure, but light absorption and attenuation increase reducing external quantum efficiency
Solution Approach 1:
The patent changes the optical parameters of the DBR structure by introducing roughened interfaces and varying refractive indices, which modifies the reflection characteristics. This reduces the number of total reflections and associated light absorption, resolving the contradiction between light containment and energy loss
3Productivity
If the DBR structure uses layers with different refractive indices to improve reflection, then optical performance is enhanced, but adhesion between layers may be compromised leading to backside chipping
Solution Approach 1:
The patent applies local quality by roughening specific interfaces within the DBR structure where optical reflection occurs, while maintaining good adhesion at critical bonding interfaces. This localized approach preserves both optical performance and layer adhesion, preventing backside chipping
Solution Approach 2:
The patent employs preliminary action by pre-treating or designing the interface structure to ensure both optimal optical reflection and strong adhesion before the chipping risk occurs during manufacturing. This preventive approach maintains layer integrity while achieving optical enhancement
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 design effectively increases the luminous efficiency of LEDs by reducing total reflection and improving light transmission, while also enhancing the adhesion between layers, thus preventing backside chipping and increasing production yield.
Implementation Method 1
According to Snell's law, when an incident light is transmitted from one medium having a high refractive index to another medium having a low refractive index, total reflection might occur if an incident angle of the incident light is greater than a critical angle of the incident light.
Implementation Method 2
the DBR structure might include plural sets of at least two semiconductor material layers or dielectric material layers which are alternately stacked, to thereby exhibit a high reflectivity within a certain optical wavelength range
Data Source
AI summary
A light-emitting diode includes a semiconductor light-emitting stack and a distributed Bragg reflector (DBR) structure. The semiconductor light-emitting stack has a first surface and a second surface opposite to each other. The DBR structure is disposed on one of the first surface and the second surface of the semiconductor light-emitting stack, and includes at least one set of light-transmitting layers including at least two of the light-transmitting layers which have different refractive indices and roughened interface.