Micro LED Stack Bandgap Layout for Electron Overflow Control
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Solution Overview
Problem
Existing LED elements for displays in mobile devices and AR/VR devices require ultra-small sizes with high luminous efficiency and reliability, but face issues with electron overflow and hole loss due to non-radiative combinations, leading to decreased luminous efficiency.
Innovation Solution
A light emitting stack with a P-type nitride semiconductor layer having a specific bandgap distribution and an N-type nitride semiconductor layer with a superlattice and electron retardation layer, along with optimized electrode connections, to enhance electron and hole recombination efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the LED element size is reduced to ultra-small dimensions (200 μm or less, especially 20 μm or less), then the display resolution and suitability for AR/VR devices is improved, but the luminous efficiency decreases due to electron overflow and hole loss from non-radiative combinations
Solution Approach 1:
The patent applies local quality by creating spatially varying Al content distributions within the P-type nitride semiconductor layer. The Al content is higher near the active layer interface and decreases toward the electrode interface, creating localized regions with different bandgap energies. This gradient structure optimizes carrier confinement and reduces non-radiative recombination specifically in the ultra-small LED element, thereby maintaining luminous efficiency at reduced sizes.
Solution Approach 2:
The patent changes the bandgap parameter of the P-type nitride semiconductor layer by controlling Al content distribution. By adjusting the Al composition ratio (x in AlxInyGazN) and creating a gradient profile, the bandgap energy is optimized to prevent electron overflow and hole loss. This parameter optimization enables ultra-small LED elements to maintain high luminous efficiency despite their reduced dimensions.
2Volume of moving object
If the LED element size is reduced to ultra-small dimensions (200 μm or less, especially 20 μm or less), then the display resolution and suitability for AR/VR devices is improved, but the reliability decreases due to electron overflow and hole loss
Solution Approach 1:
The patent implements local quality through a P-type nitride semiconductor layer with non-uniform Al content distribution. The higher Al content region near the active layer provides strong carrier confinement, while the gradient transition reduces defect formation. This localized structural optimization enhances the reliability of ultra-small LED elements by preventing electron overflow and hole loss that would otherwise lead to device degradation.
Solution Approach 2:
The patent uses a composite nitride semiconductor structure combining different Al content regions within the P-type layer. This composite approach creates a material system with optimized properties: the high-Al region provides bandgap engineering for carrier confinement, while the gradient structure minimizes dislocation density. Together, these features enhance the reliability of ultra-small LED elements.
3Reliability
If the Al content in the P-type nitride semiconductor layer is increased to prevent electron overflow, then the bandgap increases and electron confinement is improved, but the hole injection efficiency may decrease
Solution Approach 1:
The patent optimizes the Al content parameter by creating a gradient distribution rather than using a uniform high-Al composition. The Al content is highest near the active layer interface (providing strong electron confinement) and gradually decreases toward the electrode interface (maintaining hole injection efficiency). This parameter gradient resolves the contradiction between electron confinement and hole injection.
Solution Approach 2:
The patent applies local quality by creating distinct Al content regions within the P-type nitride semiconductor layer. The high-Al region near the active layer optimizes electron confinement, while the lower-Al region near the electrode optimizes hole injection. This spatial differentiation of material composition resolves the trade-off between electron confinement and hole injection 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 solution improves luminous efficiency and reliability of ultra-small LED elements by reducing electron overflow and hole loss, enhancing light emission uniformity and brightness.
Implementation Method 1
The P-type nitride semiconductor layer has a first surface, adjacent to the active layer, and a second surface, opposite to the first surface, and includes AlxInyGazN (0≤x<y<1, 0≤z≤1-x-y) having a bandgap not increasing from the second surface toward the first surface
Implementation Method 2
an N-type nitride semiconductor layer with a superlattice and electron retardation layer, along with optimized electrode connections, to enhance electron and hole recombination efficiency
Implementation Method 3
a light emitting stack including an active layer between an N-type nitride semiconductor layer and a P-type nitride semiconductor layer
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A light emitting element (100) is provided. The light emitting element (100) includes: a light emitting stack (40) including an active layer (60) between an N-type nitride semiconductor layer (50) and a P-type nitride semiconductor layer (70), the light emitting stack (40) having a width of 5 nm or more and 200 µm or less; a first electrode (82) connected to the N-type nitride semiconductor layer (50); and a second electrode (84) connected to the P-type nitride semiconductor layer (70). The P-type nitride semiconductor layer (70) has a first surface, adjacent to the active layer (60), and a second surface, opposite to the first surface, and includes AlxInyGazN (0≤x < 1, 0≤y < 1, 0 < z≤1), and a bandgap of the p-type nitride semiconductor layer (70) does not increase in a stacking direction from the second surface to the first surface. The N-type nitride semiconductor layer (50) includes a superlattice layer (52) and an electron retardation layer (53).