GaN LED Quantum Wells with Indium-Riched Auxiliary Layers
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Solution Overview
Problem
Gallium nitride (GaN) LEDs face significant challenges in maintaining luminous intensity due to high defect densities and lattice mismatch with sapphire substrates, particularly at ultraviolet wavelengths, leading to reduced light emission efficiency as the wavelength shifts from blue to ultraviolet.
Innovation Solution
The LED design incorporates indium-riched regions and specific layer structures, including quantum wells and barrier layers with tailored indium concentrations and lattice constants, along with protuberances on the N-face of the GaN substrate to enhance carrier recombination and adjust the total reflection angle, thereby increasing luminous intensity across the 222 nm-405 nm wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the luminous wavelength of the LED shifts from blue to ultraviolet, then the indium concentration in the active layer decreases, but the self-assembled indium-riched regions are lessened and carrier recombination becomes non-radiative, drastically decreasing luminous intensity
Solution Approach 1:
The patent introduces an auxiliary layer with higher indium concentration than the light emitting layer, creating localized indium-riched regions within the quantum well structure. This local quality enhancement ensures that even at ultraviolet wavelengths where bulk indium concentration is low, there are still sufficient indium-riched regions to facilitate radiative recombination and maintain high luminous intensity.
2Illumination intensity
If a large quantity of defects are generated at the lattice interface due to lattice mismatch between GaN and sapphire substrate, then the light emitting intensity decays drastically, but the defects are unavoidable during the growth process
Solution Approach 1:
The patent converts the harmful effect of lattice mismatch and defects into a beneficial one by utilizing the defects as nucleation sites for self-assembled indium-riched regions. These regions, which would normally be considered defect-related, are transformed into functional structures that enhance carrier recombination efficiency and maintain luminous intensity, especially at ultraviolet wavelengths.
3Illumination intensity
If the concentration of indium decreases gradually in the active layer when wavelength shifts to ultraviolet, then the self-assembled indium-riched regions are lessened, but maintaining luminous efficiency becomes increasingly difficult
Solution Approach 1:
The patent segments the quantum well into two distinct layers: the light emitting layer with lower indium concentration optimized for ultraviolet emission, and the auxiliary layer with higher indium concentration dedicated to forming indium-riched regions. This segmentation allows each layer to fulfill its specific function independently, maintaining both the desired wavelength emission and sufficient indium-riched regions for radiative recombination.
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 approach effectively enhances the luminous intensity of GaN LEDs by increasing carrier recombination rates and reducing total reflection, resulting in improved power extraction and efficiency, even at ultraviolet wavelengths where traditional LEDs suffer from significant intensity loss.
Implementation Method 1
Since the quantum confinement effect of the self-assembled indium-riched regions is capable of increasing the carrier recombination rate
Implementation Method 2
when a current is applied to the semiconductor materials, electrons therein would be combined with holes and release excessive energy in a form of light
Implementation Method 3
the total reflection angle of light emitted from the LED can be effectively adjusted to enhance the power extraction
Data Source
AI summary
A light emitting diode including a substrate, a p-type and n-type semiconductor layers, an active layer, a first and second electrodes is provided. The active layer is located between the n-type and p-type semiconductor layers, and includes i quantum wells and (i+1) quantum barrier layers, each quantum well is located between any two of the quantum barrier layers, each of k quantum wells among the i quantum wells is constituted of a light emitting layer and an auxiliary layer, in which an indium concentration of the auxiliary layer is greater than an indium concentration of the light emitting layer, where i and k are natural numbers greater than or equal to 1 and k≦i. The first electrode and second electrodes are located on the n-type semiconductor layer and the p-type semiconductor layer, respectively.