Continuous Nitride Layer Coalescence Using Creep-Section Pads
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Solution Overview
Problem
Existing methods for producing nitride layers in micro-LEDs suffer from high defect densities due to dislocations and misalignments during epitaxial growth, which are not effectively addressed by current solutions like ELOG and pendeo-epitaxy, leading to structural defects that degrade device performance.
Innovation Solution
A method involving the use of pads with creep sections and crystalline sections on a substrate, where the pads are arranged to allow progressive coalescence between coalesced and isolated crystallites, enabling the creep sections to accommodate misalignments and disorientations, thereby reducing structural defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hetero-substrates are used with epitaxial lateral overgrowth (ELOG) methods, then the defect density is reduced, but the dislocations are distributed non-uniformly which poses problems during device manufacture
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 and uniform defect distribution across the entire substrate area.
Solution Approach 2:
Pads are pre-formed on the substrate before epitaxial growth begins. These pads serve as predetermined nucleation sites that guide the subsequent crystallite growth and coalescence process, ensuring uniform defect distribution from the outset.
2Ease of manufacture
If conventional pendeo-epitaxy is used to make material epitaxially overgrow on preexisting pads, then overgrowth on masks is avoided, but the appearance of defects generated by coalescence of adjacent germs cannot be significantly reduced
Solution Approach 1:
The relative positions and dimensions of pads are precisely controlled to optimize coalescence behavior. By adjusting pad spacing, size, and arrangement parameters, the method achieves complete coalescence with minimal defects while maintaining process simplicity.
Solution Approach 2:
The epitaxial growth process continues until complete coalescence of crystallites occurs, forming a continuous defect-free nitride layer. The process maintains continuous growth conditions that prevent defect formation throughout the entire coalescence sequence.
3Strength
If crystallites are made to coalesce on rigid pads, then structural support is provided, but mechanical stresses from coalescence cannot be accommodated leading to high defect densities
Solution Approach 1:
The pads are designed with creep sections that provide controlled mechanical compliance. This dynamic characteristic allows pads to deform and accommodate misalignments during crystallite coalescence, reducing defect formation while maintaining overall structural integrity.
Solution Approach 2:
The mechanical properties of pads are modified by incorporating creep sections with specific viscosity parameters. These parameter changes enable pads to exhibit time-dependent deformation behavior that accommodates coalescence stresses while providing necessary structural support.
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
During epitaxy, the portion of the pad which is formed by the creep section reaches (or exceeds) its vitreous transition temperature or a temperature which is very close to the latter. Under the force of a mechanical stress, this pad portion 560 can thus be deformed
Implementation Method 2
making a crystallite epitaxially grow on at least some of said pads and continuing the epitaxial growth of the crystallites until coalescence of the crystallites carried by the pads of the assembly of pads
Data Source
AI summary
The invention relates to a method for obtaining a layer at least partially made of a nitride (N), first comprising the provision of a stack comprising at least one assembly of pads (1000A1-1000B4) extending from a substrate (100). Each pad comprises at least one creep section (220A1-220A5) and one crystalline section (300A1,300A5) surmounting the creep section (200A1-200A5). Then, a crystallite (510A1-510A5) is epitaxially grown on at least some of said pads until coalescence of the crystallites, so as to form a nitride layer (550A). The pads of the assembly are distributed over the substrate, such that the relative arrangement of the pads of the assembly is such that during the epitaxy of the crystallites, the progressive coalescence of the crystallites is always done between, on the one hand, a crystallite or a plurality of coalesced crystallites and, on the other hand, an isolated crystallite.