High voltage monolithic LED chip with improved reliability
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Solution Overview
Problem
Conventional LED chips face efficiency limitations due to total internal reflection and absorption by barrier layers, particularly in high power or high current operations, where electromigration can lead to performance degradation and failure.
Innovation Solution
The design minimizes the exposure of non-reflective barrier layers around mirror components, uses patterned barrier layers that do not wrap around the edges of mirrors, and incorporates interconnect elements with materials resistant to electromigration, such as metal alloys and dielectric layers, to enhance light extraction and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barrier layers are extended to cover the entire mirror surface for protection, then reliability is improved, but light extraction efficiency deteriorates due to absorption by non-reflective barrier materials
Solution Approach 1:
The barrier layer is applied selectively only to specific regions of the mirror surface where protection is needed, rather than covering the entire surface. This localized application maintains the high reflectivity of exposed mirror areas while providing protection where barrier material is present, thus resolving the contradiction between reliability and light extraction efficiency
Solution Approach 2:
The mirror surface is divided into protected regions (covered by barrier layer) and exposed regions (without barrier layer). This segmentation allows different portions of the mirror to serve different functions: protected areas provide reliability while exposed areas maximize light extraction, thereby resolving the contradiction
2Power
If conventional metal interconnect layers are used for electrical connection, then electrical conductivity is improved, but reliability deteriorates due to electromigration under high current operation
Solution Approach 1:
The interconnect structure uses composite materials combining metal layers with dielectric materials. The metal provides electrical conductivity while the dielectric material offers resistance to electromigration, thus resolving the contradiction between maintaining good electrical conductivity and improving reliability under high current operation
Solution Approach 2:
Dielectric materials are introduced as intermediary layers between or within metal interconnect layers. These dielectric intermediaries protect against electromigration while allowing electrical conduction to occur through the composite structure, resolving the contradiction between conductivity and reliability
3Device complexity
If active regions are placed in close proximity for compact design, then device complexity is reduced, but reliability deteriorates due to increased sensitivity to electromigration and heat effects
Solution Approach 1:
Dielectric materials are used as intermediary layers between closely spaced active regions and interconnect structures. These dielectric intermediaries provide electrical isolation and thermal management, enabling compact integration while maintaining reliability by reducing sensitivity to electromigration and heat effects
Solution Approach 2:
The structure employs composite materials with appropriate thermal and electrical properties positioned between active regions. These composite structures enable close spacing for compact design while the material properties mitigate electromigration and heat accumulation, thus resolving the contradiction between complexity reduction and reliability maintenance
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 approach increases the overall emission efficiency of LED chips by reducing light absorption and electromigration, leading to improved reliability and performance under high power conditions.
Implementation Method 1
A reflective layer is included on the interconnection metal layer arranged to reflect light that would otherwise be absorbed by the interconnection metal layer
Implementation Method 2
Light emitting diodes (LED or LEDs) are solid state devices that convert electric energy to light
Data Source
AI summary
Monolithic LED chips are disclosed comprising a plurality of active regions on a submount, wherein the submount comprises integral electrically conductive interconnect elements in electrical contact with the active regions and electrically connecting at least some of the active regions in series. The submount also comprises an integral insulator element electrically insulating at least some of the interconnect elements and active regions from other elements of the submount. The active regions are mounted in close proximity to one another to minimize the visibility of the space during operation. The LED chips can also comprise layers structures and compositions that avow improved reliability under high current operation.