Nitride Semiconductor Light Emitting Device Multilayer Intermediate Layer
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Solution Overview
Problem
Nitride semiconductor light emitting devices, such as GaN-based LEDs, suffer from crystal defects due to lattice mismatch with heterogeneous substrates, leading to reduced luminance and reliability, and existing methods to mitigate these defects are complex and costly.
Innovation Solution
A nitride semiconductor light emitting device with a multilayer intermediate layer having three or more layers with different band-gaps, such as AlGaN/GaN/InGaN or InGaN/GaN/AlGaN, is introduced between the substrate and the n-type nitride semiconductor layer to reduce crystal defects by effectively bending and stopping dislocation propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitride semiconductor is grown on heterogeneous substrate, then device can be manufactured, but crystal defects occur due to lattice mismatch
Solution Approach 1:
The patent introduces an intermediate layer composed of three or more nitride semiconductor layers with different band-gaps between the heterogeneous substrate and the active layer. This intermediate layer acts as a mediator that gradually transitions the lattice structure, reducing the abrupt mismatch between the substrate and the nitride semiconductor layer, thereby decreasing dislocation density and improving crystal quality while maintaining manufacturability on heterogeneous substrates.
Solution Approach 2:
The intermediate layer is segmented into multiple sub-layers (three or more) with progressively varying band-gaps. This segmentation allows the lattice mismatch to be distributed and managed in steps rather than as a single abrupt transition, effectively reducing dislocation propagation while maintaining the overall structural integrity and manufacturability of the device.
2Reliability
If buffer layer is used to relieve lattice mismatch, then some defects are reduced, but significant density of crystal defects remains in the active layer
Solution Approach 1:
Instead of using a single buffer layer, the patent employs an intermediate layer system with multiple nitride semiconductor layers of different band-gaps. This multi-layer intermediary provides a more effective gradient transition that better matches the lattice structures, significantly reducing dislocation density in the active layer compared to conventional single buffer layer approaches.
Solution Approach 2:
The intermediate layer is constructed as a composite structure with three or more nitride semiconductor layers having different band-gaps. This composite material approach allows optimization of each sub-layer's properties to collectively address the lattice mismatch problem more effectively than a homogeneous buffer layer, resulting in superior crystal quality in the active layer.
3Manufacturing precision
If selective epitaxial growth method is used to prevent crystal defects, then defect density is reduced, but process becomes complicated and manufacturing cost increases
Solution Approach 1:
The patent achieves improved crystal quality by changing the band-gap parameter across the intermediate layer structure. By selecting materials with different band-gaps in a systematic sequence, the method provides a straightforward approach to reducing dislocation density without requiring complex selective epitaxial growth processes, thereby simplifying manufacturing while maintaining high crystal quality.
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 multilayer intermediate layer significantly reduces crystal defects, enhancing the luminance and reliability of the light emitting device by improving crystal quality and increasing reverse breakdown voltage and optical power.
Implementation Method 1
A nitride semiconductor light emitting device with a multilayer intermediate layer having three or more layers with different band-gaps, such as AlGaN/GaN/InGaN or InGaN/GaN/AlGaN, is introduced between the substrate and the n-type nitride semiconductor layer to reduce crystal defects by effectively bending and stopping dislocation propagation.
Data Source
AI summary
Disclosed herein is a nitride semiconductor light emitting device, which is improved in luminance and reliability. The light emitting device, comprises an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate, an n-side electrode formed on a portion of an upper surface of the n-type nitride semiconductor layer, and at least one intermediate layer formed between the substrate and the n-type nitride semiconductor layer. The intermediate layer has a multilayer structure of three or more layers having different band-gaps, and is positioned below the n-side electrode.