GaN Light Emitting Element Refractive Index Correction Layer
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Solution Overview
Problem
Conventional semiconductor light emitting elements face challenges in simultaneously reducing lattice mismatch between the substrate and the first cladding layer and achieving light confinement in the vertical direction, as increasing the Al composition ratio in the first cladding layer enhances light confinement but increases lattice mismatch.
Innovation Solution
Incorporating a first refractive index correction layer of In1-x-yAlGaN between the substrate and the first cladding layer, where x and y satisfy specific composition ratio relations, to reduce lattice mismatch and enhance light confinement in the vertical direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the Al composition ratio in the first cladding layer is increased to enhance light confinement in the vertical direction, then light confinement is improved, but lattice mismatch between the substrate and the first cladding layer increases
Solution Approach 1:
The first cladding layer is divided into two distinct layers: a lower cladding layer with lower Al composition (smaller refractive index difference) and an upper cladding layer with higher Al composition (larger refractive index difference). This segmentation allows each layer to perform its function optimally - the lower layer maintains lattice matching with the substrate while the upper layer provides strong light confinement.
Solution Approach 2:
Different regions of the cladding structure are assigned different Al composition ratios tailored to their specific functional requirements. The lower cladding layer uses lower Al composition (closer to substrate lattice constant) for mechanical stability, while the upper cladding layer uses higher Al composition for optical confinement, optimizing local properties for local functions.
2Device complexity
If a single-layer first cladding layer is used, then the structure is simple, but it is difficult to simultaneously achieve light confinement and reduce lattice mismatch
Solution Approach 1:
The cladding structure is segmented into multiple layers with progressively increasing Al composition ratios from bottom to top. This segmentation transforms a single complex function (simultaneous lattice matching and light confinement) into multiple simpler, specialized functions distributed across layers.
Solution Approach 2:
The cladding structure uses a composite of multiple InAlGaN layers with different Al composition ratios, creating a graded refractive index profile. This composite structure combines the advantages of different material compositions to achieve both mechanical compatibility with the substrate and optical confinement in the active layer.
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 allows for reduced lattice mismatch and improved light confinement in the vertical direction, enabling efficient operation of the semiconductor light emitting element across various emission wavelengths.
Implementation Method 1
a first refractive index correction layer of a first conductivity type which is provided between a substrate and a first cladding layer and which includes a layer of In1-x-yAlyGaxN, where x and y satisfy the relations x/1.05+y/0.69>1, x/0.91+y/0.75≧1, and x/1.08+y/0.91≦1
Implementation Method 2
it is favorable that the first cladding layer has a high Al composition ratio, for example. On the other hand, an increased Al composition ratio in the first cladding layer results in an increased lattice mismatch between the first cladding layer and the substrate
Data Source
AI summary
A semiconductor light emitting element includes a substrate including GaN, a first cladding layer provided over the substrate, a quantum well active layer provided over the first cladding layer, a second cladding layer provided over the quantum well active layer, and a first refractive index correction layer provided between the substrate and the first cladding layer. The first refractive index correction layer includes a layer of In1-x-yAlyGaxN (where x+y<1), and x and y satisfy the relations x/1.05+y/0.69>1, x/1.13+y/0.49>1, or x/1.54+y/0.24>1, and the relations x/0.91+y/0.75≧1 and x/1.08+y/0.91≦1.