Continuous Nitride Layer Growth Through Progressive Crystallite Coalescence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for fabricating nitride layers in micro-LEDs and other optoelectronic devices suffer from high defect densities due to structural defects like dislocations, which are difficult to eliminate using conventional epitaxial growth techniques, especially when heterosubstrates are used.
Innovation Solution
A process involving the use of pads with creep segments and crystalline segments, where the pads are arranged to allow progressive coalescence between coalesced and isolated crystallites, enabling the creep segments to accommodate misalignments and misorientations, thereby reducing structural defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional epitaxial growth is used on heterosubstrates, then manufacturing cost and substrate availability are improved, but defect density increases due to lattice mismatch and dislocation coalescence
Solution Approach 1:
The substrate surface is segmented into multiple isolated pads rather than a continuous surface. Each pad serves as an independent nucleation site for crystallite growth, allowing controlled coalescence while maintaining lattice orientation. This segmentation enables the use of heterosubstrates while reducing defect density by preventing random dislocation coalescence.
Solution Approach 2:
Pads are pre-formed on the heterosubstrate before epitaxial growth begins. These pads serve as predetermined nucleation sites that guide the subsequent crystallite growth and coalescence process, ensuring that material deposition occurs only at desired locations with proper orientation from the outset.
2Reliability
If lateral overgrowth with masks is used, then dislocation density is reduced, but uniformity of defect distribution deteriorates
Solution Approach 1:
The mask layer is completely removed after initial crystallite formation on pads, eliminating the masking effect that causes non-uniform defect distribution. This allows subsequent material deposition to occur uniformly across the entire surface while the previously formed crystallites maintain their low-defect structure.
Solution Approach 2:
The process enables continuous material deposition across the entire substrate surface after mask removal, rather than being constrained by mask patterns. The useful action of material growth continues uniformly across all areas while maintaining the benefits of pad-based nucleation.
3Ease of manufacture
If pendeo-epitaxy is used to grow material on pre-existing patches, then mask growth is avoided, but defect density from germ coalescence is not significantly reduced
Solution Approach 1:
The physical state of the pad material is changed from crystalline to amorphous by heating above its melting point during the growth process. This parameter change allows the pad to flow and accommodate misorientations between coalescing crystallites, thereby reducing defect density while maintaining the simplified pendeo-epitaxy approach.
4Stability of the object's composition
If crystallites are allowed to coalesce freely, then continuous layer formation is achieved, but structural defects increase at coalescence joints
Solution Approach 1:
Amorphous material is deposited beforehand on the substrate to form pads that will serve as cushioning elements during crystallite coalescence. When crystallites coalesce, any misorientations or stresses are absorbed by the deformable amorphous pad material, preventing the formation of structural defects at coalescence joints while maintaining layer continuity.
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 nitride layers with significantly reduced defect densities, enabling the production of high-performance electronic and optoelectronic devices such as LEDs and vertical transistors with improved reliability and efficiency.
Implementation Method 1
a first segment, called the creep segment, formed in an amorphous material having a glass transition temperature Tglass transition
Implementation Method 2
Under mechanical stress, this portion of the pad can thus deform
Implementation Method 3
grow by epitaxy a crystallite on at least some of said pads and continue the epitaxial growth of the crystallites until coalescence
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
The invention relates to a method for obtaining a layer made at least in part of a nitride (N), comprising firstly providing a stack comprising at least one set of pads (1000A1-1000B4) extending from a substrate (100). Each pad comprises at least one creep section (220A1-220A5) and a crystalline section (300A1,300A5) overlying the creep section (200A1-200A5). A crystallite (510A1-510A5) is then grown by epitaxy on at least some of said pads until the crystallites coalesce to form a nitride layer (550A). The plots of the whole are distributed on the substrate in such a way that the relative arrangement of the plots of the whole is such that during the epitaxy of the crystallites, the progressive coalescence of the crystallites always takes place between on the one hand a crystallite or a plurality of coalesced crystallites and on the other hand an isolated crystallite.