Nitride Semiconductor Light-Emitting Device With Off-Angle Substrate
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Solution Overview
Problem
Current nitride semiconductor light-emitting devices with high In composition suffer from low luminous efficiency due to deteriorated crystal quality and increased planar defects, which hinder the achievement of high luminous efficiency.
Innovation Solution
A nitride semiconductor light-emitting device is designed with a nitride semiconductor substrate having an off-angle of 0.4° or larger with respect to the (0001) plane, featuring a second semiconductor layer with In composition of 2% or higher, and an active layer with a well layer and barrier layer structure to inhibit the generation of planar defects, thereby enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the In composition of the nitride semiconductor layer is increased to shift the emission wavelength to a longer wavelength, then the emission wavelength range is extended, but the crystal quality is deteriorated and luminous efficiency is lowered
Solution Approach 1:
The patent applies local quality by creating an InGaN underlayer with intermediate In composition (higher than the active layer) specifically at the growth interface. This localized region with tailored composition serves to improve crystal quality at the critical interface without requiring the entire structure to have high In content, thus enabling long-wavelength emission while maintaining acceptable crystal quality
Solution Approach 2:
The InGaN underlayer acts as an intermediary between the GaN buffer layer and the InGaN active layer. This intermediate layer with graded In composition mediates the lattice mismatch and reduces dislocation density, allowing the high-In active layer to be grown with better crystal quality than would be possible with direct growth on GaN
2Illumination intensity
If the In composition of the nitride semiconductor layer is increased to shift the emission wavelength to a longer wavelength, then the emission wavelength range is extended, but luminous efficiency is lowered
Solution Approach 1:
The patent creates a localized InGaN underlayer region with intermediate In composition that specifically addresses the interface between GaN and high-In InGaN. This local compositional adjustment reduces dislocation density at the critical growth interface, thereby improving luminous efficiency in the high-In active layer without requiring the entire structure to have optimized composition
Solution Approach 2:
The InGaN underlayer is grown preliminarily before the active layer to prepare the growth interface. This preliminary layer with intermediate In composition pre-reduces the lattice mismatch and dislocation density, creating a better foundation for subsequent high-In active layer growth and thus preserving luminous efficiency
Data Source
AI summary
A nitride semiconductor light-emitting device having high luminous efficiency is provided. A nitride semiconductor light-emitting device is provided with a nitride semiconductor substrate including a main surface having an off angle of 0.4° or larger with respect to a (0001) plane, a first semiconductor layer formed of an n-type or p-type nitride semiconductor formed on the main surface, a second semiconductor layer formed of a nitride semiconductor having In composition of 2% or higher formed on the first semiconductor layer, an active layer formed on the second semiconductor layer including a well layer formed of a nitride semiconductor having In composition higher than that of the second semiconductor layer and a barrier layer formed of a nitride semiconductor stacked therein, and a third semiconductor layer formed on the active layer having a conductivity type different from that of the first semiconductor layer.