Epitaxial Light-Extraction Pattern Transfer by Lateral Overgrowth
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Solution Overview
Problem
Existing methods for improving light extraction and directionality in III-nitride semiconductor devices, such as LEDs and laser diodes, are limited by their dependence on crystal orientation and lack of control over light emission, particularly for nonpolar and semipolar surfaces, and require delicate fabrication processes like photonic crystals.
Innovation Solution
A method involving III-nitride epitaxial lateral overgrowth (ELO) layers with a growth restrict mask to pattern island-like semiconductor layers, allowing for light extraction and guiding features without chemical etching, enabling devices to be fabricated on wings of these layers and transferred to other substrates for improved crystal quality and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a separate mask process is used for transferring patterns to the light-emitting layer and extraction electrode layer, then pattern transfer precision is improved, but the number of manufacturing steps increases and productivity decreases
Solution Approach 1:
The patent combines the light-emitting layer pattern transfer and extraction electrode layer pattern transfer into a single mask process. A single mask layer is formed with first openings for the light-emitting layer pattern and second openings for the extraction electrode layer pattern, allowing both patterns to be transferred simultaneously in one step, thereby improving productivity while maintaining precision
Solution Approach 2:
The single mask layer serves multiple functions: it defines patterns for both the light-emitting layer and extraction electrode layer, acts as a barrier layer, and enables simultaneous pattern transfer for multiple layers, replacing what would traditionally require separate specialized masks for each layer
2Manufacturing precision
If conventional separate masking is used, then each layer pattern can be controlled independently, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple masking operations into a single masking step using one mask layer that contains both first openings and second openings, reducing the number of masking processes from two separate operations to one unified operation, thereby simplifying the device complexity while maintaining independent pattern control
Solution Approach 2:
The single mask layer is segmented into different regions with first openings and second openings that serve different functions, allowing independent pattern definition for the light-emitting layer and extraction electrode layer within a unified mask structure, achieving both simplicity and precision
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 method enhances light extraction and directionality, reduces dislocation densities, and facilitates scalable manufacturing of high-yield devices independent of crystal orientations, with applications in micro-LEDs and VCSELs.
Implementation Method 1
a light-emitting layer comprising a hole transport layer, an organic compound layer, and an electron transport layer which are stacked in this order from below, wherein the organic compound layer includes a first region and a second region
Implementation Method 2
an extraction electrode layer which is positioned below the light-emitting layer and has a function of extracting light from the light-emitting layer
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Light emitting devices having light extraction or guiding structures integrated in their epitaxial layers, wherein the light extraction and guiding structures are fabricated using a lateral epitaxial growth technique that transfers a pattern from a growth restrict mask and/or host substrate to the epitaxial layers.