Top Reflector Contact for Light Emitting Devices
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Solution Overview
Problem
Conventional light emitting devices, such as UV LEDs, face challenges in efficiently extracting light due to opaque or light-absorbing top layers, and incorporating a top-side electrical contact is hindered by dielectric reflectors that block electrical current.
Innovation Solution
The implementation of a highly reflective top metal or conductive layer with a mesh or grid pattern, or a dielectric layer followed by a metal layer, allows for both enhanced light extraction and electrical current distribution, using materials like silver, gold, or dielectrics to achieve high reflectivity without compromising current spreading ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dielectric reflector is used above the top layers, then light extraction efficiency is improved, but electrical current distribution is blocked
Solution Approach 1:
The patent applies composite materials by combining a dielectric layer with a metal layer to form a reflector structure. The dielectric layer provides high reflectivity for light extraction (up to 90%), while the metal layer provides electrical conductivity for current distribution. This composite structure resolves the contradiction by integrating the optical properties of dielectrics with the electrical properties of metals in a single reflector component.
2Adaptability or versatility
If a top-side electrical contact is incorporated, then device functionality is improved, but light extraction is hindered by opaque or light-absorbing layers
Solution Approach 1:
The patent makes the top contact layer multi-functional by designing it to serve both as an electrical contact and as a reflector. The contact layer incorporates a mesh or grid pattern that allows it to conduct electricity while also reflecting light back toward the active region, thereby eliminating the need for separate electrical contact and reflector structures.
Solution Approach 2:
The patent segments the top contact layer into a mesh or grid pattern with open spaces. This segmentation allows light to pass through the open areas while the metal portions provide both electrical conductivity and light reflection. The segmented structure enables the contact layer to perform multiple functions simultaneously without compromising either electrical or optical performance.
3Reliability
If a mesh or grid pattern is used in the top contact layer, then current spreading ability is maintained, but reflectivity is reduced compared to solid layers
Solution Approach 1:
The patent compensates for the reduced reflectivity of mesh patterns by combining them with a dielectric layer. The dielectric layer provides the high reflectivity (up to 90%) needed for efficient light extraction, while the mesh pattern in the metal layer maintains current spreading ability. The composite structure achieves both high reflectivity and good current distribution.
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 significantly improves light extraction efficiency while maintaining effective current distribution, achieving reflectivity rates up to 90% and enabling flexible contact region designs for improved packaging and heat extraction.
Implementation Method 1
The ability to efficiently extract light from light emitting device structures is always a key consideration in their design... It is therefore desirable to place a reflector above the top layers so light travelling upwards can be reflected downwards toward the bottom output
Data Source
AI summary
According to one described embodiment, a light emitting device structure includes an epitaxial contact layer disposed on an active region of the light emitting device structure, a multi-layer reflector disposed at least partially on the epitaxial contact layer, and conductive contacts abutting the epitaxial contact layer, the multi-layer reflector enclosing the conductive contacts.