Flip-Chip LED With Composite DBR Structure for Reflectance and Coverage
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Solution Overview
Problem
Conventional flip-chip light-emitting diodes (LEDs) face challenges such as gaps forming on the semiconductor light-emitting stack during DBR structure deposition, leading to short-circuits and inadequate reflectance due to the use of PECVD for insulating layers and electron beam evaporation or magnetron sputtering for DBR structures.
Innovation Solution
The proposed solution involves a flip-chip LED structure with a first and second transparent dielectric layer, where the first transparent dielectric layer has a thickness greater than λ/2n1 and the second transparent dielectric layer has a thickness of mλ/4n2, with m being an odd number, to form an anti-reflective coating structure that enhances reflectance and prevents short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PECVD is used to form the insulating layer and DBR structure to ensure good covering capability, then the platform is fully covered and short-circuit is prevented, but the reflectance is lower and the reflective wavelength range is narrower
Solution Approach 1:
The patent uses a composite DBR structure combining SiO2 and Si3N4 layers with different refractive indices. The Si3N4 layers provide high reflectance due to their higher refractive index, while the SiO2 layers provide good covering capability. This composite approach resolves the contradiction by leveraging the complementary strengths of different materials.
Solution Approach 2:
The patent optimizes the thickness parameters of each DBR layer to achieve both good covering capability and high reflectance. By carefully controlling the thickness of SiO2 and Si3N4 layers, the structure achieves constructive interference for reflected light while maintaining complete coverage of the platform.
2Reliability
If the thickness of PECVD dielectric layer is increased to ensure coverage, then covering capability is improved, but the variation in thickness increases leading to larger reflectance variation
Solution Approach 1:
The patent divides the single thick dielectric layer into multiple thinner alternating layers of SiO2 and Si3N4. Each layer is thinner and easier to control with precise thickness, reducing cumulative thickness variation while maintaining complete coverage through the stacked structure.
Solution Approach 2:
By using composite SiO2 and Si3N4 layers, the patent achieves both coverage and reduced thickness variation. The alternating structure allows each layer to be deposited with better thickness control, and the composite nature maintains high reflectance despite individual layer variations.
3Use of energy by moving object
If DBR structure is formed by electron beam evaporation or magnetron sputtering to increase reflectance, then reflectance is improved, but gaps form on the corner of the platform leading to short-circuit
Solution Approach 1:
The patent combines PECVD and electron beam evaporation/magnetron sputtering to form a composite DBR structure. The PECVD process ensures complete coverage with no gaps, while the evaporated/sputtered Si3N4 layers provide high reflectance. This sequential composite formation resolves the contradiction between coverage and reflectance.
Solution Approach 2:
The patent merges two different deposition processes (PECVD and electron beam evaporation/magnetron sputtering) into a single DBR structure. The PECVD SiO2 layers provide coverage, while the evaporated/sputtered Si3N4 layers provide reflectance, achieving both goals simultaneously through process combination.
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 configuration improves the reflectance of the flip-chip LED by reducing the adverse effects of thickness variations in the dielectric layers, thereby enhancing production stability and meeting reflectance requirements across different interfaces.
Implementation Method 1
a distributed Bragg reflector (DBR) structure... having a high refractive index dielectric layer and a low refractive index dielectric layer
Implementation Method 2
distributed Bragg reflector (DBR) structure
Implementation Method 3
an insulating layer having a certain thickness is formed on a surface of a semiconductor light-emitting stack using plasma enhanced chemical vapor deposition (PECVD)
Implementation Method 4
forming a distributed Bragg reflector (DBR) structure having a high refractive index dielectric layer and a low refractive index dielectric layer on the insulating layer using electron beam evaporation
Implementation Method 5
forming a distributed Bragg reflector (DBR) structure having a high refractive index dielectric layer and a low refractive index dielectric layer on the insulating layer using electron beam evaporation or magnetron sputtering
Data Source
AI summary
A flip-chip light-emitting diode includes a first conductivity type semiconductor layer, a light-emitting layer, a second conductivity type semiconductor layer, a first transparent dielectric layer, a second transparent dielectric layer, and a distributed Bragg reflector (DBR) structure which are sequentially stacked. The first transparent dielectric layer has a thickness greater than λ/2n1, wherein A is an emission wavelength of the light-emitting layer, n1 is a refractive index of the first transparent dielectric layer, n2 is a refractive index of the second transparent dielectric layer and is greater than n1, and n2 is lower than a refractive index of the second conductivity type semiconductor layer. A light-emitting apparatus including the aforesaid flip-chip light-emitting diode is also provided.