Nitride Semiconductor Light Extraction via Low Refractive Index Protrusions
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Solution Overview
Problem
Semiconductor light emitting devices face inefficiencies in light extraction due to large refractive index differences between crystal layers and air, and surface roughening methods lack reproducibility, leading to non-uniform device characteristics.
Innovation Solution
A semiconductor light emitting device structure featuring a low refractive index protrusion part, such as AlN, on the light extraction face with a shape like an equilateral hexagonal pillar, which improves light extraction efficiency and reduces surface roughness variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surface roughening is applied to improve light extraction efficiency, then light extraction efficiency is improved, but device characteristics become non-uniform due to poor reproducibility
Solution Approach 1:
The patent changes the parameter of surface treatment from conventional roughening to laser processing with specific parameters (wavelength, pulse duration, scan speed, overlap rate) to achieve controlled and reproducible surface modification that improves light extraction while ensuring manufacturing precision
Solution Approach 2:
The patent replaces mechanical/chemical surface roughening methods with laser processing, substituting a process with poor reproducibility with one that offers precise control through adjustable parameters, thereby improving both light extraction efficiency and manufacturing consistency
2Productivity
If transparent conductive film is deposited on rough surface to improve light extraction, then light extraction efficiency is improved, but film disconnection occurs reducing reliability
Solution Approach 1:
The patent modifies the surface treatment parameters to create a moderately rough surface that maintains film adhesion while improving light extraction, balancing the competing requirements of enhanced optical performance and film continuity
Solution Approach 2:
The laser-processed surface acts as an intermediary structure that provides both light extraction enhancement and adequate adhesion for the transparent conductive film, mediating between the conflicting requirements of roughness for optics and smoothness for film continuity
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
Enhances light extraction efficiency while maintaining reproducibility and reducing the risk of transparent conductive film disconnection, resulting in more uniform device performance.
Implementation Method 1
when a difference between the refractive index of a crystal layer forming a light extraction face and the refractive index of the air is large, it is not possible to extract light efficiently
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes a first semiconductor layer, a light emitting layer, a second semiconductor layer, and a low refractive index layer. The first semiconductor layer has a first major surface and a second major surface being opposite to the first major surface. The light emitting layer has an active layer provided on the second major surface. The second semiconductor layer is provided on the light emitting layer. The low refractive index layer covers partially the first major surface and has a refractive index lower than the refractive index of the first semiconductor layer.