Glass-Substrate LED Structure for Low-Temperature GaN Growth
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Solution Overview
Problem
The challenge of forming high-quality gallium nitride semiconductor films on amorphous glass substrates at lower temperatures due to their low heat-resistant temperature, which is less than 800°C, and the difficulty in efficiently separating LED devices on glass substrates using existing scribing methods.
Innovation Solution
The use of an amorphous glass substrate with a compensation layer having a thermal expansion coefficient greater than the substrate but less than the semiconductor layers, combined with a passivation layer that extends to the scribe region, allows for the formation of a nitride semiconductor stack and efficient separation of LED devices using laser or mechanical scribing without affecting the substrate's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gallium nitride semiconductor film is formed on an amorphous glass substrate by MOCVD or HVPE, then high-quality semiconductor films can be produced, but the substrate temperature must be lowered below 800°C due to the substrate's low heat-resistant temperature, resulting in poor crystallinity
Solution Approach 1:
A buffer layer is introduced as an intermediary between the amorphous glass substrate and the gallium nitride semiconductor layer. This buffer layer enables high-quality semiconductor film formation at lower temperatures (below 800°C) by providing a suitable crystalline foundation that compensates for the substrate's temperature limitations, thus resolving the contradiction between maintaining low substrate temperature and achieving high crystallinity.
Solution Approach 2:
The invention uses a composite structure consisting of the amorphous glass substrate, a buffer layer, and the gallium nitride semiconductor layer. The buffer layer material is specifically selected to have thermal expansion characteristics that bridge the gap between the glass substrate and the semiconductor layer, enabling stable film formation at reduced temperatures while maintaining high crystallinity.
2Productivity
If scribing is performed to separate LED devices on glass substrates, then individual devices can be obtained, but existing laser or mechanical scribing methods may damage the substrate or fail to achieve clean separation
Solution Approach 1:
The invention introduces a scribe line region that is structurally segmented from the main LED device regions. This scribe line region has a different layer configuration (without the semiconductor stack) that is specifically designed to facilitate clean separation. The segmentation allows scribing to occur in a dedicated zone without affecting the integrity of the LED devices, thus improving both separation efficiency and substrate reliability.
Solution Approach 2:
The scribe line region has locally different properties compared to the LED device regions. Specifically, the scribe line area lacks the semiconductor stack and has a simplified structure, making it more suitable for scribing operations. This local quality differentiation enables clean separation while preserving the integrity of the main device areas.
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 enables the production of high-quality LED devices on larger amorphous glass substrates with improved crystallinity and facilitates efficient separation, allowing for increased productivity and versatility in device shape and size, while maintaining substrate integrity during scribing.
Implementation Method 1
A compensation layer on the second surface of the amorphous glass substrate. A coefficient of thermal expansion of the compensation layer exceeds a coefficient of thermal expansion of the amorphous glass substrate and is less than a coefficient of thermal expansion of a semiconductor layer forming the nitride semiconductor stacked structure.
Implementation Method 2
The laser scribing method locally heats the irradiation region of the laser beam.
Data Source
AI summary
An LED device includes an amorphous glass substrate having a first surface and a second surface opposite to the first surface; a buffer layer arranged on the first surface of the amorphous glass substrate; a nitride semiconductor stacked structure including an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer on the buffer layer; a passivation layer covering the nitride semiconductor stacked structure; an n-electrode in contact with the n-type nitride semiconductor layer, and a p-electrode in contact with the p-type nitride semiconductor layer; and a compensation layer on the second surface of the amorphous glass substrate. A coefficient of thermal expansion of the compensation layer exceeds a coefficient of thermal expansion of the amorphous glass substrate and is less than a coefficient of thermal expansion of a semiconductor layer forming the nitride semiconductor stacked structure.