Micro LED Reflector Stack for Sub-200 μm Light Loss
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Solution Overview
Problem
Micro LEDs with sizes of 200 μm or less face challenges in handling and light efficiency due to light loss, making it difficult to implement high-efficiency micro-scale light emitting devices for micro LED displays.
Innovation Solution
A micro-scale light emitting device design featuring a semiconductor stack with a distributed Bragg reflector in the insulation layer and a metal reflection layer covering the side surfaces, along with a transparent substrate and light blocking layer, enhances light extraction and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro LED size is reduced to 200 μm or less for high-resolution displays, then display resolution is improved, but light efficiency deteriorates due to increased light loss
Solution Approach 1:
The patent converts the harmful light loss from side surfaces into beneficial light extraction by applying reflective layers to redirect trapped light toward the top emission surface, and uses the previously wasted side-emitted light for color conversion to generate additional useful light output
Solution Approach 2:
The patent changes the optical parameters of the micro LED structure by introducing distributed Bragg reflectors with specific refractive index layers and thicknesses, and by applying metal reflective layers with optimized geometry, to transform the optical field distribution and improve light extraction efficiency
2Measurement precision
If micro LED size is reduced to 200 μm or less, then display resolution is improved, but handling difficulty increases
Solution Approach 1:
The patent segments the micro LED fabrication process into distinct stages: growing LED structures on large-area substrates, patterning arrays of micro LEDs, transferring complete arrays to display panels, and individually addressing them through pixel circuits. This allows mass handling of large substrates rather than manual handling of individual micro LEDs
Solution Approach 2:
The patent employs a nested approach where multiple micro LEDs are arranged in arrays on large substrates, which are then transferred as complete arrays to display panels. The pixel circuits are integrated within the same substrate structure, creating a hierarchical nesting from micro LED level to array level to panel level
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
Improves light efficiency and facilitates mass production of high-efficiency micro-scale light emitting devices suitable for micro LED displays.
Implementation Method 1
the insulation layer includes a distributed Bragg reflector
Implementation Method 2
a metal reflection layer disposed on the insulation layer, and covering at least a portion of the side surface of the semiconductor stack
Data Source
AI summary
A light emitting device is a micro-scale light emitting device including a semiconductor stack, an insulation layer, and a metal reflection layer. The semiconductor stack includes a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. The insulation layer covers upper and side surfaces of the semiconductor stack. The metal reflection layer is disposed on the insulation layer, and covers at least a portion of the side surface of the semiconductor stack. The insulation layer includes a distributed Bragg reflector.