Nanorod Light Emitting Device Reducing Crystal Defects
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Solution Overview
Problem
Semiconductor light emitting devices, particularly those with nitride-based compound semiconductors, suffer from reduced luminous efficiency due to crystal defects such as lattice mismatch dislocations and threading dislocations, which lead to increased leakage current and heat energy emission instead of light energy.
Innovation Solution
A nanorod light emitting device structure is developed with a mask layer having through holes for vertically growing light emitting nanorods, grouped into nanoclusters with a conductor covering each group, and a grid-patterned first electrode for reduced current density and improved luminous efficiency, utilizing a nitride semiconductor layer with a core/shell structure to minimize crystal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a thin film structure is used for light emitting devices, then the device complexity is reduced, but crystal defects increase due to lattice mismatch and thermal expansion differences
Solution Approach 1:
The patent divides the light emitting device into multiple independent nanorod units arranged in an array, where each nanorod acts as a separate light emitting element. This segmentation reduces the area of lattice mismatch and thermal expansion differences at the substrate interface, thereby minimizing crystal defects while maintaining structural simplicity
Solution Approach 2:
The patent transitions from a planar thin film structure to a three-dimensional nanorod array structure. By growing nanorods vertically from the substrate through through-holes in a mask layer, the device achieves better crystal quality by limiting the lateral spread of defects while maintaining a relatively simple overall structure
2Illumination intensity
If the light emitting area is increased to improve brightness, then the luminous efficiency may be reduced due to increased current density and heat generation
Solution Approach 1:
The patent segments the light emitting area into multiple independent nanorod units, each with its own current path through the mask layer. This segmentation distributes the total current across many individual nanorods, reducing the current density in each unit and thereby improving luminous efficiency while maintaining high overall brightness through the cumulative effect of all nanorods
Solution Approach 2:
The mask layer provides localized current injection to each nanorod through individual through-holes, creating optimal current distribution at the nanorod bases. This localized quality control ensures uniform current density across all nanorods, preventing hot spots and improving overall luminous efficiency
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
The nanorod structure reduces crystal defects, enhances light emission area, and decreases leakage current, thereby improving luminous efficiency and light extraction efficiency.
Implementation Method 1
Semiconductor light emitting devices use electroluminescence, i.e., a phenomenon whereby light is emitted from a semiconductor layer due to application of a current or a voltage. When electrons and holes are combined in an active layer of a semiconductor light emitting device, energy corresponding to an energy bandgap of the active layer may be emitted in the form of light.
Data Source
AI summary
A nanorod light emitting device includes at least one nitride semiconductor layer, a mask layer, multiple light emitting nanorods, nanoclusters, a filling layer disposed on the nanoclusters, a first electrode and connection parts. The mask layer is disposed on the nitride semiconductor layer and has through holes. The light emitting nanorods are disposed in and extend vertically from the through holes. The nanoclusters are spaced apart from each other. Each of the nanoclusters has a conductor and covers a group of light emitting nanorods, among the multiple light emitting nanorods, with the conductor. The first electrode is disposed on the filling layer and has a grid pattern. The connection parts connect the conductor and the first electrode.