GaN LED Transparent Electrodes Grain Size Control
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Solution Overview
Problem
Existing semiconductor light emitting devices face challenges in achieving excellent electrical characteristics and processability, particularly in the conductive layers used in GaN-based blue or green light emitting diodes, where the contact resistance and grain size of the conductive layers affect the device's performance and manufacturing efficiency.
Innovation Solution
The use of polycrystalline conductive layers with specific grain diameters and sputtering methods to form transparent electrodes, where the second conductive layer has a smaller average grain diameter of 150 nanometers or less, and the first conductive layer has a larger diameter, optimizing contact resistance and processability while maintaining high transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is used in GaN-based light emitting diodes, then electrical characteristics such as volume resistivity and contact resistance are improved, but processability deteriorates due to grain size control requirements
Solution Approach 1:
The conductive layer is segmented into multiple layers with different grain diameter characteristics. The first conductive layer has a first average grain diameter, while the second conductive layer has a second average grain diameter that is smaller than the first. This segmentation allows each layer to be optimized for different functions: the first layer provides good electrical characteristics, while the second layer with smaller grains improves processability and reduces contact resistance.
Solution Approach 2:
Different regions of the conductive structure are given different grain diameter properties. The first conductive layer maintains larger grains for optimal electrical conductivity, while the second conductive layer specifically at the contact region has smaller grains (150 nm or less) to enhance contact properties and reduce contact resistance. This local differentiation resolves the contradiction between overall electrical performance and contact-specific processability.
2Reliability
If the average grain diameter of the second conductive layer is reduced to 150 nanometers or less, then contact resistance is reduced and processability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the grain diameter parameter of the second conductive layer to 150 nm or less, which is smaller than the first conductive layer. This parameter change directly reduces contact resistance and improves processability. The controlled variation in grain diameter between layers achieves the desired electrical properties without requiring complex manufacturing processes, as the grain size control is integrated into the layer formation process.
3Illumination intensity
If transparent conductive layers are used for light extraction, then optical transmittance is improved, but electrical characteristics such as contact resistance may deteriorate
Solution Approach 1:
The conductive structure uses a composite of multiple conductive layers with different grain diameter characteristics. The first conductive layer provides good electrical conductivity with larger grains, while the second conductive layer with smaller grains (≤150 nm) specifically addresses contact resistance. This composite structure maintains high optical transmittance while achieving low contact resistance, resolving the contradiction between optical and electrical performance.
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 results in semiconductor light emitting devices with improved electrical characteristics and processability, achieving low contact resistance and high transmittance, thus enhancing the overall performance and manufacturing efficiency of the devices.
Implementation Method 1
a first film serving as the second conductive layer is formed on the second semiconductor layer in an atmosphere of a noble gas by a sputtering method using a first electric power
Implementation Method 2
the first conductive layer and the second conductive layer are formed by subjecting the first film and the second film to a heat treatment in an atmosphere including oxygen
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes first and second conductive layers, a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a light emitting part. The second semiconductor layer is provided between the first conductive layer and the first semiconductor layer. The light emitting part is provided between the first and second semiconductor layers. The second conductive layer is in contact with the second semiconductor layer and the first conductive layer between the second semiconductor layer and the first conductive layer. The first and second conductive layers are transmittable to light emitted from the light emitting part. The first conductive layer includes a polycrystal having a first average grain diameter. The second conductive layer includes a polycrystal having a second average grain diameter of 150 nanometers or less and smaller than the first average grain diameter.