Monolithic LED Pixel Arrays With Dielectric Isolation
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Solution Overview
Problem
Existing LED arrays face reliability and mechanical stability issues due to the use of metal side-contacts, which can lead to light output degradation and electrical leakage, especially during the laser lift-off process for substrate removal, and may result in pixel failure and optical crosstalk.
Innovation Solution
The implementation of a light emitting diode (LED) array with a monolithic body, non-segmented pixels, a common cathode, and dielectric materials to insulate the anodes and the cathode, eliminating the need for deep metal trenches and enhancing optical efficiency and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If metal side-contacts are used to provide reflective sidewalls and electrical cathode, then optical contrast is maximized and light scattering is reduced, but optical absorption increases due to limited metal reflectivity
Solution Approach 1:
The patent introduces dielectric materials as intermediary substances between the metal contact and the light path. These dielectric layers serve as mediators that reflect light more efficiently than metal alone, reducing optical absorption while maintaining the electrical cathode function. The dielectric material acts as a buffer that improves optical performance without compromising electrical connectivity.
2Reliability
If deep metal trenches are used to ensure low sheet and contact resistance, then electrical conductivity is improved, but mechanical stability decreases and cracks may form during processing
Solution Approach 1:
The patent changes the depth parameter of the trenches, making them shallow rather than deep. This parameter modification reduces mechanical stress and prevents crack formation during laser lift-off and other processing steps, while still achieving adequate electrical conductivity through optimized contact geometry and material selection.
Solution Approach 2:
The patent employs composite structures combining metal contacts with dielectric materials. This composite approach allows the metal to provide electrical conductivity while the dielectric material provides mechanical support and stress relief, preventing cracks and improving overall structural stability during processing and operation.
3Use of energy by moving object
If the substrate is removed by laser lift-off to enhance light extraction, then optical efficiency is improved, but the side contacts are damaged causing light output degradation and electrical leakage
Solution Approach 1:
The patent applies preliminary protective actions by coating the metal side-contacts with dielectric materials before the laser lift-off process. This preliminary protection shields the contacts from laser-induced damage during substrate removal, preventing subsequent light output degradation and electrical leakage while still allowing effective light extraction.
4Reliability
If etching trenches stop before contacting the substrate surface to protect metal contacts, then contact integrity is maintained, but remaining EPI layer is prone to cracking and delamination
Solution Approach 1:
The patent uses composite materials where dielectric layers are deposited over the remaining EPI layer at the trench bottom. This composite structure prevents cracking and delamination of the EPI layer while maintaining contact protection, as the dielectric material provides mechanical reinforcement and stress 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 improves mechanical stability, reduces optical absorption, and maximizes optical efficiency by minimizing dark-grid appearance and pixilation effects, while maintaining electrical injection efficiency without the need for segmentation of epitaxial layers.
Implementation Method 1
one or more dielectric materials insulating: the second portion of the N-type layer, the active region, and the P-type layer from the common cathode; the plurality of anodes from each other; and the plurality of anodes from the common cathode
Implementation Method 2
A light emitting diode (LED) is a semiconductor light source that emits light when current flows through it
Implementation Method 3
A light emitting diode (LED) is a semiconductor light source that emits light when current flows through it
Implementation Method 4
LEDs combine a p-type semiconductor with an n-type semiconductor
Data Source
AI summary
A light emitting diode (LED) array comprises non-segmented pixels in a light-emitting pixel area providing optical efficiency and minimizing dark-grid appearance. The LED array comprises: a monolithic body, a light-emitting pixel area, a plurality of anodes, a common cathode, and one or more dielectric materials. The light-emitting pixel area is integral to the monolithic body. The light-emitting pixel area includes semiconductor layers comprising: a second portion of an N-type layer, an active region, and a P-type layer. The monolithic body comprises a first portion of an N-type layer, and the second portion of the N-type layer is integral to the first portion of the N-type layer. Each anode comprises a P-contact layer and one or more P-contact materials, each P-contact layer is in contact with the P-type layer. The common cathode comprises one or more N-contact materials in contact with the first portion of the N-type layer.