LED Mesa Structure with Current Blocking Layer for Droop Suppression
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Solution Overview
Problem
Light emitting diodes (LEDs) face challenges in maintaining stable operation and luminous efficacy when driven at high currents, particularly due to the droop phenomenon, which causes a rapid decrease in efficiency, and require improvements in current spreading efficiency and mechanical reliability.
Innovation Solution
The design incorporates a light emitting diode structure with a first conductivity type semiconductor layer, multiple mesas of a second conductivity type semiconductor layer, an active layer, a current blocking layer, a transparent electrode layer, and electrodes, featuring connecting and protruding portions to enhance current spreading and reliability, with a symmetrical structure to reduce current crowding and improve luminous uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional LED structure is used for high current driving, then current density is high, but droop phenomenon occurs causing rapid decrease in luminous efficacy
Solution Approach 1:
The LED structure is divided into multiple mesas (first mesa, second mesa, third mesa, fourth mesa) instead of a single continuous structure. This segmentation increases the active area for light emission while distributing the current load, thereby reducing current density and suppressing the droop phenomenon at high current driving conditions
Solution Approach 2:
Different regions of the LED are given different properties: the mesas provide localized light emission zones with specific conductivity types, the current blocking layer is strategically positioned to control current flow paths, and the transparent electrode layer is configured to optimize both electrical connection and light extraction in different areas
2Reliability
If current blocking layer covers entire exposed region, then current spreading is restricted, but mechanical reliability improves
Solution Approach 1:
The current blocking layer is applied selectively to specific regions (portions of mesas and specific portions of the exposed region) rather than uniformly across the entire structure. This localized application allows current to spread efficiently in regions where it is needed while providing mechanical support and reliability in regions where blocking is required
3Ease of manufacture
If asymmetric electrode configuration is used, then manufacturing is simpler, but current crowding occurs reducing luminous uniformity
Solution Approach 1:
The first and second electrodes are configured asymmetrically with respect to the mesa structure, with the first electrode having a first bonding pad and the second electrode having a second bonding pad positioned at different locations. This asymmetric configuration simplifies the manufacturing process while the current blocking layer and transparent electrode layer are designed to compensate for potential current crowding effects
Solution Approach 2:
The current blocking layer and transparent electrode layer are strategically positioned in different regions to optimize both the asymmetric electrode configuration and current distribution, ensuring uniform luminous output despite the asymmetric electrode placement
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 effectively suppresses the droop phenomenon, improves luminous uniformity, and enhances the mechanical reliability of the LED by ensuring efficient current distribution and preventing defects such as bonding pad detachment, thereby maintaining high current driving stability and efficiency.
Implementation Method 1
A light emitting diode (LED) refers to a solid-state device that emits light through conversion of electric energy
Data Source
AI summary
A light emitting diode including a first semiconductor layer and a plurality of mesas including a second semiconductor layer and an active layer interposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer including an exposed region between the plurality of mesas, a current blocking layer disposed on a portion of the plurality of mesas and a portion of the exposed region, a transparent electrode layer covering the second semiconductor layer and the current blocking layer, and a second electrode disposed on the current blocking layer and the transparent electrode layer and electrically connected to the second semiconductor layer. The current blocking layer includes a connecting portion extending from a first mesa to a second mesa adjacent to the first mesa and a protruding portion protruding from the connecting portion and disposed on the exposed region.