Microcavity GaN Pixel Structure on Glass for Light Extraction
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Solution Overview
Problem
The high manufacturing cost of micro LED display devices and the difficulty in forming gallium nitride films on amorphous glass substrates, which results in decreased light extraction efficiency due to the high refractive index of gallium nitride.
Innovation Solution
A light emitting device is developed with a gallium nitride film formed on an amorphous glass substrate using a sputtering method, incorporating a microcavity structure with a semi-transparent reflective layer and insulating alignment layers to enhance light extraction efficiency and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gallium nitride film is formed on amorphous glass substrate, then manufacturing cost is reduced, but light extraction efficiency decreases due to high refractive index mismatch
Solution Approach 1:
An amorphous aluminum oxide layer is introduced as an intermediary between the amorphous glass substrate and the gallium nitride film. This intermediate layer has a refractive index that bridges the gap between the substrate and the high-refractive-index gallium nitride, reducing optical reflection and improving light extraction efficiency while maintaining the cost advantage of using amorphous glass substrate
Solution Approach 2:
The refractive index profile is modified by introducing the aluminum oxide intermediate layer with specific optical properties. This parameter change in the optical path creates a gradual transition in refractive index, reducing the abrupt mismatch that causes light reflection and improving overall light extraction from the LED structure
2Reliability
If high temperature MOCVD or HVPE is used to form gallium nitride film, then film quality is improved, but substrate cost increases and process complexity increases
Solution Approach 1:
The conventional high-temperature MOCVD or HVPE processes are replaced with a sputtering method. This substitution uses physical vapor deposition instead of chemical vapor deposition, enabling gallium nitride film formation at lower temperatures with simplified equipment and processes while maintaining acceptable film quality for LED applications
Solution Approach 2:
The deposition temperature parameter is significantly reduced by switching from MOCVD/HVPE to sputtering. This parameter change allows the use of amorphous glass substrates that cannot withstand high temperatures, while the sputtering process maintains sufficient film crystallinity and quality through controlled deposition conditions
3Reliability
If conventional LED chip transfer method is used for micro LED display, then device performance is maintained, but manufacturing cost increases
Solution Approach 1:
The gallium nitride film is formed directly on the amorphous glass substrate in the desired LED pixel array configuration before final device assembly. This preliminary formation of functional structures on the final substrate eliminates the need for subsequent chip transfer operations, reducing manufacturing steps and costs while maintaining device performance
Solution Approach 2:
The expensive LED chip transfer process is extracted and eliminated from the manufacturing flow. Instead of forming LEDs on separate chips and transferring them to the display substrate, the invention integrates LED formation directly into the substrate fabrication process, removing the unnecessary intermediate transfer step
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 improves light extraction efficiency and maintains stability across chromaticity changes, while reducing manufacturing costs by using an amorphous glass substrate for forming gallium nitride-based light emitting devices.
Implementation Method 1
A light emitting device is developed with a gallium nitride film formed on an amorphous glass substrate using a sputtering method
Implementation Method 2
incorporating a microcavity structure with a semi-transparent reflective layer and insulating alignment layers to enhance light extraction efficiency
Data Source
AI summary
A light emitting device includes a plurality of pixels arranged in a matrix in a first direction and in a second direction orthogonal to the first direction. Each of the plurality of pixels includes an amorphous substrate, a semi-transparent reflective layer over the amorphous substrate, a first insulating alignment layer over the semi-transparent reflective layer, a first semiconductor layer over the first insulating alignment layer, a light emitting layer over the first semiconductor layer, a second semiconductor layer over the light emitting layer, and an electrode layer over the second semiconductor layer. Each of the first semiconductor layer, the light emitting layer, and the second semiconductor layer includes gallium nitride.