III-Nitride LED Buffer Structure for Green Gap Emission
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Solution Overview
Problem
The production of efficient LEDs that can emit longer wavelength light, such as in the green to red spectrum, is hindered by phase segregation of InGaN alloys, lack of lattice-matched substrates, difficulty in p-type doping, and piezo- and pyro-electric polarization, leading to reduced recombination efficiency and inefficient UV-LEDs.
Innovation Solution
A template for selective area growth of group III-nitride devices is used, involving the formation of columnar structures with a buffer layer of silicon, germanium, and carbon, which enables the deposition of InGaN alloy films to enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If InGaN alloy films are deposited to emit longer wavelength light, then the wavelength range is extended, but phase segregation occurs reducing recombination efficiency
Solution Approach 1:
A multi-layer buffer structure comprising AlN, GaN, and SiGeC layers is introduced as an intermediary between the substrate and the InGaN active layer. This buffer structure mediates the lattice mismatch and reduces dislocation density, enabling high-quality InGaN film growth at longer wavelengths while maintaining recombination efficiency by preventing phase segregation through controlled strain management.
Solution Approach 2:
The composition and thickness parameters of the buffer layers are precisely controlled to manage strain in the InGaN alloy. By adjusting the SiGeC layer composition and the overall buffer structure, the patent optimizes the growth conditions to prevent phase segregation and maintain high recombination efficiency across extended wavelength ranges.
2Reliability
If lattice matched substrates are used to reduce crystal defects, then device performance is improved, but substrate availability is limited
Solution Approach 1:
The patent employs a multi-layer buffer structure as an intermediary between dissimilar substrates (such as silicon or sapphire) and the InGaN active layers. This buffer system compensates for lattice mismatch, enabling high-performance device growth on commonly available substrates without requiring rare lattice-matched substrates, thus improving both substrate availability and device performance.
Solution Approach 2:
The invention uses composite buffer structures combining multiple materials (AlN, GaN, SiGeC) to achieve lattice matching compensation. This composite approach allows the system to adapt to different substrate types while maintaining high crystal quality and device performance, significantly expanding substrate availability options.
3Loss of energy
If selective area growth is used to improve light emission efficiency, then recombination efficiency is enhanced, but fabrication complexity increases
Solution Approach 1:
The patent employs selective area growth where the buffer structure and active layers are grown in discrete columnar regions separated by trenches. This segmentation allows independent optimization of each growth region while using standardized buffer templates, thereby enhancing recombination efficiency in the active areas while keeping the overall fabrication process manageable through modular, repeatable units.
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 allows for the fabrication of LEDs that can efficiently emit light in the green/yellow wavelength range, overcoming the challenges of phase segregation and lattice mismatch, thereby improving the recombination efficiency and addressing the 'green gap' in nitride LED technology.
Implementation Method 1
A template for selective area growth of group III-nitride devices is used, involving the formation of columnar structures with a buffer layer of silicon, germanium, and carbon, which enables the deposition of InGaN alloy films to enhance light emission efficiency.
Data Source
AI summary
Group III-Nitride LED devices having efficient wavelength emissions across the visible light spectrum and a method for their fabrication. Templates for the epitaxial growth of these compound semiconductors on silicon and silicon substrates are provided for the selective area growth of low dislocation density crystalline Group III-Nitride alloys, such as GaN, InGaN, and the like on crystalline, lattice-mismatched substrates. The method describes the formation of the Si(x)C(y)Ge buffer layer using the deposition from sources of Ge, C and Si that enables the growth of a high crystalline quality III-Nitride layer, such as GaN, through the insertion of Si(x)C(y)Ge buffer layer at the interface between silicon and III-Nitride film.