CAAC-OS Substrate for GaN LED Crystal Quality
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Solution Overview
Problem
The crystal quality of light-emitting layers in gallium nitride-based light-emitting devices is often compromised by the use of inexpensive substrates, leading to inefficiencies and reduced durability, necessitating the development of substrates with improved crystal quality for enhanced productivity in manufacturing.
Innovation Solution
A c-axis-aligned crystal region (CAAC-OS) metal oxide semiconductor substrate is used as a supporting substrate for light-emitting devices, with heat treatment at high temperatures to form a CAAC-OS substrate, which includes layers like gallium, indium, and zinc, and is stacked over base substrates like sapphire or yttria-stabilized zirconia, with a buffer layer to reduce lattice mismatch and improve crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inexpensive substrates like sapphire are used, then manufacturing cost is reduced, but crystal quality of light-emitting layer deteriorates
Solution Approach 1:
A buffer layer is introduced as an intermediary between the sapphire substrate and the light-emitting layer. This buffer layer has a lattice constant intermediate between sapphire and the light-emitting layer, reducing lattice mismatch and improving crystal quality without requiring expensive substrates.
Solution Approach 2:
The patent uses a composite structure consisting of sapphire substrate, buffer layer, and light-emitting layer. Each layer is optimized for its specific function, creating a composite material system that achieves both cost-effectiveness and high crystal quality.
2Manufacturing precision
If gallium nitride single crystal substrate is used, then crystal quality of light-emitting layer is improved, but manufacturing complexity increases
Solution Approach 1:
The buffer layer serves as a mediator that simplifies the substrate requirement. Instead of needing complex gallium nitride single crystal substrates, the patent uses a simple sapphire substrate with an added buffer layer, reducing manufacturing complexity while maintaining high crystal quality.
3Ease of manufacture
If lattice mismatch is not addressed, then manufacturing process is simplified, but emission efficiency deteriorates
Solution Approach 1:
The buffer layer acts as a mediator that addresses lattice mismatch without complicating the manufacturing process. It provides a gradual transition in lattice constant, reducing dislocation density and improving emission efficiency while maintaining process simplicity.
4Manufacturing precision
If buffer layer is added to reduce lattice mismatch, then crystal quality is improved, but device structure becomes more complex
Solution Approach 1:
The patent segments the device structure into distinct functional layers: sapphire substrate, buffer layer, and light-emitting layer. This segmentation allows each layer to be optimized independently, improving crystal quality while keeping the overall structure manageable and systematic.
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 allows for the formation of light-emitting devices with favorable crystal quality and high productivity, enabling efficient manufacturing of gallium nitride-based LEDs with improved emission efficiency and durability.
Implementation Method 1
The CAAC-OS substrate is subjected to heat treatment at a high temperature of approximately 700° C. to 1500° C. in manufacture.
Implementation Method 2
a single crystal film is grown in order to form a crystal surface which is epitaxially grown
Implementation Method 3
The buffer layer is a film having a function of reducing lattice mismatch in the case where the lattice constant of the CAAC-OS substrate is different from that of the light-emitting diode layer
Implementation Method 4
a single crystal film is grown in order to form a crystal surface which is epitaxially grown
Data Source
AI summary
To provide a novel light-emitting device that can be manufactured with high productivity. In a light-emitting device in which a light-emitting diode (LED) layer is provided over a substrate, a metal oxide semiconductor (c-axis aligned crystalline oxide semiconductor (CAAC-OS)) substrate including a crystal part having a c-axis which is substantially perpendicular to a surface of the substrate is used as the substrate. The substrate may have either a single-layer structure of a CAAC-OS substrate or a structure in which a thin CAAC-OS substrate is stacked over a base substrate.