Self-Supporting Gallium Nitride Substrate for Vertical LED Structures
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high cost and limited availability of large-area single crystal substrates for light emitting devices, such as LEDs, make it challenging to produce cost-effective and high-performance devices with vertical structures, as traditional substrates like sapphire lead to dislocation and electrode formation issues.
Innovation Solution
A self-supporting gallium nitride substrate composed of a plate of gallium nitride-based single crystal grains with a single crystal structure in the normal direction is developed, using an oriented polycrystalline sintered body, seed crystal layer, and epitaxial growth to achieve a cost-effective and large-area substrate suitable for vertical LED structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large-area single crystal substrates are used, then device performance and luminous efficiency are improved, but production cost increases significantly
Solution Approach 1:
The patent uses a composite structure consisting of a sapphire substrate layer and a gallium nitride crystal layer. This composite approach allows the device to benefit from the mechanical strength and thermal stability of sapphire while achieving the electrical and optical properties of gallium nitride, thereby reducing cost compared to using large-area single crystal gallium nitride substrates
Solution Approach 2:
The gallium nitride crystal layer is grown as a separate layer on top of the sapphire substrate rather than requiring a large-area single crystal gallium nitride substrate. This segmentation allows the expensive single crystal material to be used only where necessary (in the functional layer) while using a cheaper substrate material for support
2Ease of manufacture
If sapphire substrates are used, then production cost is reduced, but dislocation occurs due to lattice mismatch
Solution Approach 1:
The patent introduces an intermediate buffer layer between the sapphire substrate and the gallium nitride crystal layer. This buffer layer acts as a mediator that gradually transitions from the sapphire lattice structure to the gallium nitride lattice structure, reducing the abrupt lattice mismatch and minimizing dislocation propagation
Solution Approach 2:
The patent changes the composition and thickness parameters of the buffer layer to optimize the transition from sapphire to gallium nitride. By carefully controlling these parameters, the lattice mismatch is managed and dislocation density is reduced while maintaining cost-effectiveness
3Ease of manufacture
If sapphire substrates are used, then cost is reduced, but electrode formation is prevented due to insulating properties
Solution Approach 1:
The patent segments the device structure into distinct functional layers: the sapphire substrate for mechanical support, the gallium nitride crystal layer for electrical and optical functions, and additional functional layers for electrode formation. This segmentation allows each layer to perform its specific function optimally
Solution Approach 2:
The gallium nitride crystal layer serves as an intermediary between the insulating sapphire substrate and the required electrical contacts. This layer provides the necessary electrical conductivity and functional properties while the sapphire substrate continues to provide mechanical support and thermal stability
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 solution provides a cost-effective alternative to single crystal substrates with improved luminous efficiency and the ability to form vertical LED structures without grain boundary interference, enhancing the production of large-area light emitting devices.
Implementation Method 1
forming a seed crystal layer composed of gallium nitride on the oriented polycrystalline sintered body so that the seed crystal layer has crystal orientation mostly in conformity with crystal orientation of the oriented polycrystalline sintered body
Implementation Method 2
forming a layer with a thickness of 20 μm or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer
Data Source
AI summary
Provided is a self-supporting gallium nitride substrate useful as an alternative material for a gallium nitride single crystal substrate, which is inexpensive and also suitable for having a large area. This substrate is composed of a plate composed of gallium nitride-based single crystal grains, wherein the plate has a single crystal structure in the approximately normal direction. This substrate can be manufactured by a method comprising providing an oriented polycrystalline sintered body; forming a seed crystal layer composed of gallium nitride on the sintered body so that the seed crystal layer has crystal orientation mostly in conformity with the crystal orientation of the sintered body; forming a layer with a thickness of 20 μm or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer; and removing the sintered body.