LED Conductive Pillar Layout for Uniform Current Distribution
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Solution Overview
Problem
Vertical and flip-chip light emitting devices face issues with uneven brightness due to high current density and thermal expansion coefficient mismatches between the patterned current blocking layer and semiconductor/reflective layers, leading to reliability problems during manufacturing and testing.
Innovation Solution
A light emitting device design featuring a die-bonding substrate, a light emitting semiconductor structure with conductive pillars, an insulating layer with trenches and openings, and electrodes, where the insulating layer's trench surrounds the edge of the light emitting area to optimize current distribution and reduce current concentration, and a metal layer fills the trench and openings to enhance adhesion and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a patterned current blocking layer is added to improve luminous efficiency, then current concentration is reduced, but current density becomes too high at the n-type conductive pillar and opening area causing epitaxial recombination efficiency deterioration and uneven brightness
Solution Approach 1:
The current blocking layer is divided into multiple segments: a first current blocking layer with a first pattern and a second current blocking layer with a second pattern. This segmentation allows different regions to have different current blocking characteristics, effectively dispersing current density and preventing excessive concentration at specific areas while maintaining overall luminous efficiency.
Solution Approach 2:
Different regions of the current blocking structure are designed with different properties. The first and second current blocking layers have different patterns and blocking strengths, creating local variations in current distribution. This allows optimal current management in different areas of the light emitting device, preventing epitaxial recombination efficiency deterioration while maintaining luminous efficiency.
2Loss of energy
If a patterned current blocking layer is added to improve luminous efficiency, then current distribution is optimized, but thermal expansion coefficient mismatch between layers causes poor product yield and reliability issues
Solution Approach 1:
An insulating layer is introduced as an intermediary between the light emitting layer and the current blocking layers. This insulating layer acts as a buffer that accommodates thermal expansion coefficient differences between layers, preventing stress concentration and delamination while allowing the current blocking structure to function effectively for luminous efficiency improvement.
Solution Approach 2:
The device employs a composite structure with multiple materials having different properties: the light emitting layer, insulating layer, and current blocking layers are combined. This composite material approach allows each layer to be optimized for its specific function while the overall structure accommodates thermal expansion differences, improving both luminous efficiency and product yield.
3Device complexity
If current is concentrated on the n-type conductive pillar to simplify structure, then manufacturing is easier, but high current density causes uneven brightness and reliability issues
Solution Approach 1:
The current blocking function is segmented into two distinct layers with different patterns. This segmentation enables current to be distributed across multiple regions rather than concentrated at a single pillar, achieving brightness uniformity while maintaining a relatively simple overall structure that can be manufactured using standard processes.
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
The design achieves even current distribution, improves luminous efficiency, and increases the device's ability to withstand external stress, thereby enhancing manufacturing yield and reliability.
Implementation Method 1
A light emitting diode (LED) is essentially a diode with a P-N junction. The combination of electron-hole pairs when the element acts on causes emission of photons.
Implementation Method 2
Each conductive pillar is in direct contact with the second-type semiconductor layer and electrically connected to the die-bonding substrate.
Data Source
AI summary
The light emitting device includes a substrate, a light-emitting semiconductor structure, conductive pillars, an insulating layer, and first and second electrodes. The light-emitting semiconductor structure includes a first-type semiconductor layer, a light-emitting layer and a second-type semiconductor layer disposed on the substrate from bottom to top. The conductive pillars are disposed in the light-emitting semiconductor structure. The conductive pillars penetrates is in contact with the second-type semiconductor layer and electrically connected to the substrate. A first portion of the insulating layer is disposed between the first-type semiconductor layer and the substrate, and a second portion of the insulating layer electrically insulates the first-type semiconductor layer and the light emitting-layer from the conductive pillars. The first electrode is electrically connected to the first-type semiconductor layer and electrically insulated from the conductive pillars. The second electrode is electrically connected to the conductive pillar.