Graded Si Barrier Layer for Near-Ultraviolet LED Efficiency
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Solution Overview
Problem
Near-ultraviolet LED devices based on nitride semiconductors face low optical efficiency due to high dislocation density and crystal defects, and existing techniques to improve emission efficiency are costly and inefficient.
Innovation Solution
A semiconductor light emitting device structure is developed with a light emitting section comprising multiple barrier layers and well layers made of AlxGa1-x-yInyN, where the nearest barrier layer has a high Si concentration on one side and a lower Si concentration on the other side, reducing electron overflow and enhancing hole confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaN layer is formed on a sapphire c-plane substrate via high-temperature growth to reduce dislocation density, then emission efficiency is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent modifies the Si concentration parameter within the barrier layer structure, creating a gradient distribution where the Si concentration varies from 1×10^19 to 1×10^21 atoms/cm³. This parameter change optimizes carrier confinement and reduces electron overflow into the p-type confinement layer, thereby improving emission efficiency without requiring expensive GaN substrate growth techniques
Solution Approach 2:
The patent employs a composite barrier layer structure consisting of multiple layers with different Si concentrations (first portion with high Si concentration, second portion with lower Si concentration). This composite structure combines the benefits of electron blocking at the interface with reduced hole scattering, achieving high emission efficiency through material composition optimization rather than expensive substrate engineering
2Reliability
If Si concentration is increased in the barrier layer to prevent electron overflow, then emission efficiency is improved, but anomalous diffusion of Mg occurs in the p-type confinement layer
Solution Approach 1:
The patent segments the barrier layer into distinct portions: a first portion adjacent to the well layer with high Si concentration (1×10^20 to 1×10^21 atoms/cm³) for electron blocking, and a second portion adjacent to the p-type confinement layer with lower Si concentration (1×10^19 to 1×10^20 atoms/cm³) to prevent Mg diffusion. This segmentation allows each portion to perform its specific function optimally without interfering with the other
Solution Approach 2:
The patent applies local quality by creating a Si concentration gradient within the barrier layer, where the Si concentration is locally optimized for different functions: high concentration near the well layer for electron confinement and lower concentration near the p-type layer for Mg diffusion prevention. This localized optimization resolves the contradiction between electron blocking and Mg stability
3Device complexity
If conventional barrier layer structure is used to simplify manufacturing, then device complexity is reduced, but electron overflow into p-type layer increases reducing emission efficiency
Solution Approach 1:
The patent changes the Si concentration parameter from a uniform value to a gradient distribution across the barrier layer thickness. This parameter modification creates distinct regions with optimized carrier concentrations, improving electron blocking efficiency while maintaining a relatively simple overall device structure that can be fabricated using standard semiconductor processing techniques
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 configuration increases the emission efficiency of near-ultraviolet LEDs by preventing anomalous diffusion of Mg and improving the resistance and reliability of the p-type confinement layer, leading to higher radiant flux and reduced operating voltage.
Implementation Method 1
preventing anomalous diffusion of Mg
Implementation Method 2
light emitting section including a plurality of barrier layers made of Si-containing AlxGa1-x-yInyN, and a well layer provided between each pair of the plurality of barrier layers and made of GaInN or AlGaInN
Data Source
AI summary
A semiconductor light emitting device includes a first layer including at least one of n-type GaN and n-type AlGaN; a second layer including Mg-containing p-type AlGaN; and a light emitting section provided between the first and second layers. The light emitting section includes barrier layers of Si-containing AlxGa1-x-yInyN (0≦x, 0≦y, x+y≦1), and a well layer provided between the barrier layers and made of GaInN or AlGaInN. The barrier layers have a nearest barrier layer nearest to the second layer among the barrier layers and a far barrier layer. The nearest barrier layer includes a first portion made of Si-containing AlxGa1-x-yInyN (0≦x, 0≦y, x+y≦1), and a second portion provided between the first portion and the second layer and made of AlxGa1-x-yInyN (0≦x, 0≦y, x+y≦1). The Si concentration in the second portion is lower than those in the first portion and in the far barrier layer.