Nitride Tile Epitaxy Using a Creep Layer to Avoid Edge Defects
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Solution Overview
Problem
The production of micro-LEDs for optoelectronic devices faces challenges due to the reduction in external quantum efficiency as the size of the micro-LEDs decreases, primarily attributed to defects caused by the engraving process used to delimit the nitride layers, leading to non-radiative recombination and reduced luminescence, especially at the edges of the LEDs.
Innovation Solution
A method involving the growth of nitride stickers on a stack comprising a substrate with a creep layer and a crystalline layer, where the creep layer deforms under mechanical stress to align and coalesce crystallites without forming dislocations, eliminating the need for engraving and reducing defects at coalescence joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of micro-LEDs is reduced to increase pixel density, then the resolution is improved, but the external quantum efficiency decreases due to increased edge effects and non-radiative recombination
Solution Approach 1:
The invention removes the harmful engraving process that creates defects at the edges of micro-LEDs. By eliminating the RIE etching step entirely and using a self-aligned growth method where quantum wells form only within the nitride vignettes during epitaxial growth, the source of edge defects is extracted from the fabrication process, thereby maintaining high efficiency even at reduced micro-LED sizes
Solution Approach 2:
The invention performs preliminary spatial delimitation of nitride vignettes before the growth of quantum wells. By defining the boundaries of nitride regions first through a controlled growth process on patterned substrates, and then allowing quantum wells to form only within these pre-defined regions during subsequent epitaxial growth, the method prevents edge defects before they can occur
2Manufacturing precision
If RIE etching is used to spatially delimit nitride vignettes, then the manufacturing precision is improved, but defects are introduced at the edges leading to non-radiative recombination
Solution Approach 1:
The invention converts the potential harm of precise patterning into a benefit by using a self-aligned growth mechanism. Instead of using aggressive RIE etching that damages edges, the method uses controlled epitaxial growth where the nitride vignettes themselves define the boundaries, and quantum wells automatically form only within these regions. The precision is achieved through growth control rather than etching, turning the growth process into the delimitation mechanism
Solution Approach 2:
The invention replaces the mechanical/chemical etching process (RIE) with a growth-based delimitation method. Instead of removing material to define boundaries, the method uses selective epitaxial growth to form nitride vignettes with precise boundaries, where the quantum wells are incorporated only within these regions during the same growth process, eliminating the need for separate etching steps
3Quantity of substance
If the perimeter-to-area ratio is increased by reducing micro-LED size, then the pixel density is improved, but the Shockley-Read-Hall recombination increases due to edge defects
Solution Approach 1:
The invention extracts the source of non-radiative recombination by eliminating the RIE etching process that creates edge defects. By using a self-aligned growth method where quantum wells form only within the nitride vignettes during epitaxial growth without subsequent etching, the harmful edge defects are removed from the system, preventing carrier trapping and non-radiative recombination even at high perimeter-to-area ratios
Solution Approach 2:
The invention performs preliminary definition of the active regions through controlled nitride vignette growth before quantum well formation. By establishing precise boundaries through the growth process itself and ensuring quantum wells form only within these boundaries during the same epitaxial growth, the method prevents edge defects from forming in the first place, eliminating non-radiative recombination pathways
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 approach results in micro-LEDs with improved brightness and resolution, reduced dislocation density, and enhanced electrical performance, enabling the production of high-efficiency micro-LEDs and power transistors with minimal defects.
Implementation Method 1
a creep layer, made of a material having a glass transition temperature, the creep layer having a glass transition temperature Tglass transition
Implementation Method 2
to grow a crystallite by epitaxy on at least some of said pads and: to continue the epitaxial growth of the crystallites until the crystallites on adjacent pads of the same set coalesce so as to form a nitride vignette
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 2C~2D
AI summary
The invention relates in particular to a process for obtaining tiles (550A, 550B) that are made at least partly of a nitride (N), the process comprising the following successive steps: - providing a stack comprising a substrate (100) at least the following layers arranged in succession from the substrate (100): - a first layer, referred to as the flow layer (200); - a second, crystalline layer, referred to as the crystalline layer (300); - forming pads (1000A1-1000B4) by etching the crystalline layer (300) and at least one portion (220) of the flow layer (200) such that: o each pad (1000A1-1000B4) comprises at least: - a first segment, referred to as the flow segment (200A1- 200B4), formed by a portion at least of the flow layer (200); - a second, crystalline segment, referred to as the crystalline segment (300A1, 300B4), formed by the crystalline layer (300) and surmounting the flow segment (200A1- 200B4); o the pads (1000A1-1000B4) are distributed over the substrate (100) so as to form a plurality of sets (1000A, 1000B) of pads (1000A1-1000B4); - epitaxially growing a crystallite (510A1-510B4) on at least some of said pads (1000A1-1000B4) and continuing the epitaxial growth of the crystallites (510A1-510B4) until reaching coalescence of the crystallites (510A1-510B4) borne by the adjacent pads (1000A1-1000B4) of one and the same set (1000A, 1000B).