Nano Array LED for Lattice Mismatch and Efficiency
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Solution Overview
Problem
Conventional semiconductor light-emitting devices (LEDs) face challenges in luminance efficiency due to lattice mismatch and thermal expansion coefficient differences between thin film InGaN layers and substrates, which decrease as the emission spectrum shifts towards longer wavelengths.
Innovation Solution
The development of a light-emitting device (LED) with a nano array layer comprising polypyramid-shaped nano structures, where a first type semiconductor nano core is grown from a dielectric layer with nano holes, and an active layer is sequentially grown on the side surface, along with a second type semiconductor layer, to reduce lattice mismatch and enhance luminance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the In content in the InGaN layer is increased to shift the emission spectrum towards longer wavelengths, then the emission wavelength increases, but the lattice mismatch between the InGaN layer and substrate increases, lowering the luminance efficiency
Solution Approach 1:
The patent divides the continuous InGaN layer into discrete nanostructures (nanopillars, nanowires, or nanocolumns) with lateral dimensions of 1-100 nm. This segmentation allows each nanostructure to be treated as an independent quantum well, maintaining high internal quantum efficiency even at longer wavelengths by reducing the total In content needed while achieving the desired emission spectrum through quantum confinement effects.
Solution Approach 2:
The patent creates local quantum well structures within the InGaN layer by forming nanostructures with different lateral dimensions. Each nanostructure acts as a localized quantum well with tailored emission properties, allowing the emission spectrum to be shifted to longer wavelengths through quantum confinement without requiring high bulk In content that would cause lattice mismatch.
2Temperature
If a thin film type InGaN layer is used to achieve long wavelength emission, then the emission spectrum moves toward longer wavelengths, but the lattice mismatch and thermal expansion coefficient difference increase, decreasing luminance efficiency
Solution Approach 1:
The patent transitions from a two-dimensional thin film structure to a zero-dimensional quantum dot or one-dimensional nanowire/nanopillar structure. By confining carriers in the lateral dimension(s) to create quantum wells with lateral dimensions of 1-100 nm, the emission wavelength is controlled by quantum confinement rather than bulk composition, enabling long wavelength emission without the lattice mismatch problems of conventional thin films.
3Temperature
If the In content is increased to achieve longer wavelength emission, then the emission spectrum shifts to longer wavelengths, but the internal quantum efficiency decreases due to increased lattice mismatch
Solution Approach 1:
The patent segments the InGaN layer into discrete nanostructures with lateral dimensions of 1-100 nm, creating multiple independent quantum wells. This segmentation allows the system to achieve long wavelength emission through quantum confinement effects while maintaining low In content in each nanostructure, thereby preserving high internal quantum efficiency by avoiding the lattice mismatch that would occur in bulk materials with high In content.
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 improves internal quantum efficiency and reduces quantum confinement stark effects, maintaining constant In content and increasing light extraction, resulting in enhanced luminance efficiency, particularly in longer wavelength bands like green or yellow.
Implementation Method 1
a first type semiconductor nano core selectively grown from the first type semiconductor layer
Implementation Method 2
an active layer, a second type semiconductor layer sequentially grown from a side surface of the first type semiconductor nano core
Implementation Method 3
Semiconductor light-emitting devices (LEDs) are high efficient and environmentally friendly light sources
Data Source
AI summary
Light-emitting devices (LED) and methods of manufacturing the same. A LED includes a first type semiconductor layer, a nano array layer that includes a plurality of nano structures each including a first type semiconductor nano core selectively grown from the first type semiconductor layer, and an active layer and a second type semiconductor layer sequentially grown from a side surface of the first type semiconductor nano core, and that is formed in a selective growth region formed in a surface of the first type semiconductor layer, a first electrode layer that is formed to be used when a voltage is applied to the first type semiconductor layer and formed in a predetermined pattern connecting regions that do not correspond to the selective growth region in the first type semiconductor layer, a second electrode layer formed to be used when a voltage is applied to the second type semiconductor layer on the plurality of nano structures, and an insulating layer formed between the first electrode layer and the second electrode layer so that the first electrode layer is insulated from the second electrode layer.