Rock Salt Nitride Buffer Layer for Light Emitting Devices
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Solution Overview
Problem
Lattice mismatch between substrates and nitride semiconductor layers in light emitting devices leads to lattice defects, affecting the stability and reliability of the devices.
Innovation Solution
Incorporating a rock salt structured nitride buffer layer between the light emitting structure and the sapphire substrate to reduce lattice mismatch and thermal expansion coefficient differences, enhancing the stability and reliability of the light emitting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a nitride semiconductor layer is formed directly on a sapphire substrate, then the device structure is simple, but lattice mismatch causes lattice defects reducing device reliability
Solution Approach 1:
A buffer layer comprising multiple nitride layers with different aluminum compositions is inserted between the sapphire substrate and the light emitting structure. This intermediate buffer layer gradually transitions the lattice constant from the sapphire substrate to the GaN light emitting layer, reducing lattice mismatch and minimizing lattice defects while maintaining device reliability
2Reliability
If a buffer layer is added to reduce lattice mismatch, then device reliability is improved, but device complexity increases
Solution Approach 1:
The buffer layer is designed with spatially varying aluminum composition, where the first nitride layer has a higher aluminum content closer to the sapphire substrate and the second nitride layer has a lower aluminum content closer to the GaN layer. This local composition gradient optimally matches lattice constants at different positions, effectively reducing lattice defects while using a relatively simple multi-layer structure
Data Source
AI summary
A light emitting device is provided that includes a substrate, a buffer layer disposed on an r-plane of the substrate, the buffer layer having a rock salt structured nitride, and a light emitting structure arranged on the buffer layer, the light emitting structure being grown in an a-plane.