InGaN Pyramids on GaN Wire Substrates for Red LED Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN-based light-emitting diodes (LEDs) with high indium concentrations face challenges in achieving red emission due to lattice parameter mismatch and structural defects, leading to reduced radiative efficiency and high manufacturing costs.
Innovation Solution
A three-dimensional structure comprising InGaN pyramids grown on a GaN-based wire substrate, where the wire acts as a 3D substrate, reducing mechanical stresses and improving crystalline quality, and allowing for higher indium incorporation and efficient epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high indium concentration ([In]≥10 at %) is incorporated to achieve red emission, then the main wavelength increases to red spectrum, but lattice parameter mismatch causes mechanical stresses and structural defects that reduce radiative efficiency
Solution Approach 1:
The patent transitions from conventional planar (2D) LED structures to three-dimensional (3D) pyramid structures. This dimensional change allows the active region to be formed as pyramids with specific crystallographic orientations that reduce lattice mismatch effects. The 3D pyramid geometry enables better strain management and reduces the formation of structural defects compared to planar structures, thereby maintaining radiative efficiency at high indium concentrations required for red emission.
Solution Approach 2:
The patent employs local quality by creating pyramidal structures with specific crystallographic orientations in different regions. The pyramids are grown with <111> or <110> orientations that provide different strain management characteristics. This local structural optimization allows high indium concentration to be maintained in the pyramid regions while managing lattice mismatch stresses through the specific geometric and crystallographic properties of each pyramid structure.
2Ease of manufacture
If planar technology with posterior structuring is used to form mesa structures, then manufacturing process is simplified, but side wall defects are created that promote non-radiative surface recombinations and reduce radiative efficiency
Solution Approach 1:
The patent applies preliminary action by forming the pyramidal structures directly during the epitaxial growth process rather than creating them through posterior structuring steps. The 3D pyramid shapes are self-organized during metalorganic vapour phase epitaxy (MOVPE) growth, eliminating the need for subsequent lithography and etching steps that would create side wall defects. This preliminary formation of the desired 3D structure prevents the introduction of harmful side wall defects while maintaining manufacturing efficiency.
3Reliability
If thick GaN buffer layer is used to improve crystal quality by confining defects, then crystal quality in upper part improves, but curvature problems occur in silicon wafer and production cost increases
Solution Approach 1:
The patent uses 3D pyramid structures grown directly on thin buffer layers or even directly on silicon substrates. The vertical growth direction of the pyramids allows defects to be confined to the base regions while the pyramid tips and upper regions maintain high crystal quality. This eliminates the need for thick buffer layers, preventing wafer curvature problems and reducing production costs while still achieving the desired crystal quality improvement.
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
The approach enhances the crystal quality and indium concentration of InGaN pyramids, enabling LEDs to emit light with improved radiative efficiency in the red spectrum while reducing production costs.
Implementation Method 1
the mismatch of lattice parameters between the GaN-based regions and the InGaN-based active region causes mechanical stresses
Implementation Method 2
radiative recombinations of electron-hole pairs occur, which allow to obtain light radiation having a main wavelength
Implementation Method 3
The growth of the InGaN pyramids can be done by epitaxy from a GaN layer partially covered by a masking layer
Data Source
AI summary
A three-dimensional (3D) structure for optoelectronics including a pyramid made of a first InGaN-based material formed from a substrate, wherein the 3D structure includes a wire made of a second GaN-based material, different from the first material, the wire extending in a longitudinal direction perpendicular to the plane of the substrate between the substrate and a base of the InGaN-based pyramid, so that the 3D structure has the general shape of a pencil. One or more embodiments of the invention also relates to a method for manufacturing such a 3D structure, and an optoelectronic device based on a plurality of these 3D structures.