LED Pixel Array Composite N-Contact for Optical Isolation
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Solution Overview
Problem
Existing LED arrays face challenges in optical efficiency due to metal side-contacts with limited reflectivity and potential damage during substrate removal, leading to optical absorption and reliability issues.
Innovation Solution
The use of a transparent conductive oxide (TCO) layer as an n-contact and dielectric material for optical isolation in LED devices, combined with an electrically conductive material in trenches, enhances optical efficiency and reduces optical absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal side-contacts are used to ensure low sheet and contact resistance, then electrical conductivity is improved, but optical efficiency deteriorates due to severe absorption in the cavity
Solution Approach 1:
The patent introduces an optical isolation layer as an intermediary between the metal side-contact and the semiconductor layers. This dielectric layer mediates the interaction by providing electrical connection through the metal contact while optically isolating the cavity to prevent absorption, thus resolving the contradiction between electrical conductivity and optical efficiency
Solution Approach 2:
The patent employs a composite structure combining metal side-contacts with dielectric optical isolation layers. This composite material approach allows the metal to provide electrical conductivity while the dielectric layer prevents optical absorption, achieving both low contact resistance and high optical efficiency simultaneously
2Reliability
If deep side contacts are extended into the bottom of the trench to optically separate pixels, then optical isolation is improved, but optical absorption increases due to limited metal reflectivity
Solution Approach 1:
The optical isolation layer acts as an intermediary that enables deep trench filling for optimal electrical contact while preventing the metal from directly interacting with propagating light modes. This mediation allows deep side contacts to provide optical separation without the penalty of metal absorption
Solution Approach 2:
The patent replaces the reliance on metal reflectivity (mechanical/optical property of metal) with a dielectric optical isolation mechanism. Instead of depending on metal to reflect light, the system uses a dielectric layer to optically isolate the cavity, substituting the optical function from metal to dielectric material
3Use of energy by moving object
If laser lift-off process is used to remove substrate for enhanced light extraction, then light extraction is improved, but side contacts are damaged causing reliability issues
Solution Approach 1:
The optical isolation layer serves as a protective cushioning layer deposited beforehand on the semiconductor layers. During the laser lift-off process, this layer protects the semiconductor and side contacts from damage while still allowing the laser to effectively remove the substrate and enhance light extraction
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 optical efficacy by minimizing optical absorption and providing effective optical isolation between neighboring pixels, resulting in increased light extraction and reliability.
Implementation Method 1
an optical isolation layer disposed between the n-contact and the electrically conductive material, the optical isolation layer comprising a dielectric material
Implementation Method 2
an n-contact disposed between the electrically conductive material in the trench and the semiconductor layers
Implementation Method 3
transparent conductive oxide (TCO) layer
Implementation Method 4
an electrically conductive material disposed in the trench
Data Source
AI summary
Arrays of light emitting diode (LED) devices in which each LED device includes a mesa having a top surface and at least one sidewall defining a trench having a bottom surface. The mesa comprises semiconductor layers including an n-type layer, an active layer, and a P-type layer, and an electrically conductive material fills the trench. An n-contact, which can be a transparent conductive oxide (TCO) layer, lines an entire surface of the sidewall and trench bottom, and a dielectric layer lines an entire length of the TCO layer, such that the dielectric layer optically isolates the trench and the n-contact functions as an n-contact and spreading layer.