GaN LED Vertical Structure Wet Etching Substrate Removal
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Solution Overview
Problem
Current methods for preparing light-emitting diodes with a vertical structure, such as laser or mechanical grinding for substrate stripping, are costly and damage the epitaxial layer, leading to low yield and inefficiencies in heat dissipation, current distribution, and light extraction.
Innovation Solution
A wet process is used to strip the GaN base epitaxial layer and sapphire substrate, involving a graphical growth substrate with high melting point materials and a sequence of layer formation and etching, including a transparent conductive film, omni-directional reflection layer, and passive metal protection, to minimize damage and enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser or mechanical grinding is used to strip the growth substrate, then the vertical structure light-emitting diode can be prepared, but the production cost increases and the epitaxial layer is damaged
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary between the sapphire substrate and the GaN epitaxial layer. This sacrificial layer is designed to be selectively removable, allowing the epitaxial layer to be released from the substrate without direct contact with harsh laser or mechanical grinding processes. The sacrificial layer acts as a buffer that protects the delicate epitaxial layer during the substrate removal process, thereby reducing damage and improving yield while maintaining cost-effectiveness.
2Ease of manufacture
If sapphire substrate is used as support substrate, then the light-emitting diode can be fabricated, but the electrical conductivity is very low and lattice constant does not match with GaN material
Solution Approach 1:
The patent segments the substrate system into multiple functional layers: the sapphire substrate provides mechanical support and thermal management, while the sacrificial layer enables controlled release, and the GaN epitaxial layer provides the active light-emitting function with proper lattice matching. This segmentation allows each layer to optimize its specific function without compromising the others, resolving the contradiction between fabrication capability and electrical/lattice properties.
3Productivity
If mechanical grinding is used to strip the growth substrate, then the substrate can be removed, but the precision is low and the grinding has non-uniformity
Solution Approach 1:
The patent replaces the mechanical grinding system with a chemical etching system. Instead of using abrasive mechanical forces that cause non-uniformity and low precision, the invention uses chemical reactions to selectively remove the sacrificial layer. This chemical approach provides more uniform and controllable removal, improving manufacturing precision while maintaining high productivity through batch processing capability.
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 method results in a light-emitting diode with improved heat dissipation, uniform current distribution, increased current density, and high light extraction efficiency, while reducing production costs and damage to the epitaxial layer.
Implementation Method 1
a method for preparing a light-emitting diode having a vertical structure by stripping a GaN base epitaxial layer and a sapphire substrate by a wet process
Data Source
AI summary
A method for preparing a light-emitting diode having a vertical structure by stripping a GaN base epitaxial layer and a sapphire substrate by a wet process, the method including: a) preparing a graphical growth substrate; b) growing a GaN base light-emitting diode epitaxial layer on the graphical growth substrate, the GaN base light-emitting diode epitaxial layer from the bottom to the top successively including a N-type GaN layer and a P-type GaN layer; c) successively forming a transparent and electrically conductive film, an omni-directional reflection layer, an electrically conductive reflection layer, and a passive metal protection layer from the bottom to the top on the GaN base light-emitting diode epitaxial layer; and d) removing the first layer of stable material with a high melting point of the growth substrate by dry etching, exposing the N-type GaN layer, and preparing an N electrode on the N-type GaN layer.