AlxGa1-xN Buffer Layer for GaN LED Lattice Mismatch
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Solution Overview
Problem
GaN-based semiconductor layers grown on sapphire substrates exhibit high defect density due to lattice mismatch, affecting the reliability, productivity, and electrical properties of light emitting diodes.
Innovation Solution
An AlxGa1-xN buffer layer with a decreasing composition ratio of Al is interposed between the substrate and the first conductive semiconductor layer, reducing lattice mismatch and defect density, and formed using techniques like MOCVD, HVPE, or MBE at specific temperature and pressure ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a GaN buffer layer is grown on a sapphire substrate, then the structure provides a base for subsequent layer growth, but the lattice mismatch between the GaN buffer layer and the sapphire substrate results in high defect density
Solution Approach 1:
An AlN buffer layer is introduced as an intermediary layer between the sapphire substrate and the GaN-based semiconductor layer. The AlN buffer layer has a lattice constant closer to that of the sapphire substrate, serving as a mediator that reduces the lattice mismatch and enables subsequent GaN layer growth with lower defect density
Solution Approach 2:
The lattice constant parameter of the buffer layer is changed from GaN to AlN, which has a different lattice constant that better matches the sapphire substrate. This parameter change in the buffer layer material composition resolves the lattice mismatch issue while maintaining the buffer layer's function
2Reliability
If a doped GaN-based conductive semiconductor layer is grown on the GaN buffer layer, then the device achieves electrical conductivity, but high stress in the layer results in high defect density
Solution Approach 1:
The AlN buffer layer serves as a stress-compensating intermediary that reduces the high stress in the doped GaN-based conductive semiconductor layer, thereby preventing stress-induced defects while maintaining the electrical conductivity of the doped layer
Solution Approach 2:
The AlN buffer layer is grown beforehand to provide a cushioning effect that compensates for the stress that would otherwise be applied to the doped GaN-based conductive semiconductor layer, preventing defect formation before the stress can cause damage
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 approach lowers defect density, improves crystallinity, surface configuration, and electrical properties of the GaN-based semiconductor layers, enhancing the overall performance of light emitting diodes.
Implementation Method 1
the AlxGa1-xN (0≦x≦1) buffer layer having the composition ratio x of Al decreasing from the substrate to the first conductive semiconductor layer is interposed to reduce lattice mismatch between the substrate and the first conductive semiconductor layer
Implementation Method 2
formed using techniques like MOCVD, HVPE, or MBE at specific temperature and pressure ranges
Data Source
AI summary
The present invention relates to a light emitting diode having an AlxGa1-xN buffer layer and a method of fabricating the same, and more particularly, to a light emitting diode having an AlxGa1-xN buffer layer, wherein between a substrate and a GaN-based semiconductor layer, the Al x Ga 1-x N (O≦x≦1) buffer layer having the composition ratio x of Al decreasing from the substrate to the GaN-based semiconductor layer is interposed to reduce lattice mismatch between the substrate and the GaN-based semiconductor layer, and a method of fabricating the same. To this end, the present invention provides a light emitting diode comprising a substrate; a first conductive semiconductor layer positioned on the substrate; and an AlxGa1-xN (O≦x≦1) buffer layer interposed between the substrate and the first conductive semiconductor layer and having a composition ratio x of Al decreasing from the substrate to the first conductive semiconductor layer.