Internal Current Confinement in LEDs to Limit Efficiency Droop
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Solution Overview
Problem
Current semiconductor-based LEDs face efficiency droop issues due to increased current density, leading to reduced luminous efficacy, and existing technologies struggle to confine current injection effectively, resulting in non-radiative recombination at external surfaces.
Innovation Solution
The development of LED devices with a confined current injection area, where a first current spreading layer pillar is doped with a specific dopant type and a second current spreading layer is doped oppositely, surrounded by a current confinement region, which laterally confines current within the active layer, reducing non-radiative recombination and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If current density is increased to improve luminous efficacy, then efficiency droop occurs leading to reduced luminous efficacy
Solution Approach 1:
The patent applies local quality by creating a current confinement region with different electrical properties than the surrounding active layer. This is achieved through lateral oxidation of the cladding layer to form a high-resistivity barrier that locally modifies current distribution, concentrating current flow in the center of the active layer away from lossy surface regions.
2Productivity
If current injection area is expanded to reduce current density, then efficiency improves but non-radiative recombination at external surfaces increases
Solution Approach 1:
The patent converts the harmful effect of surface non-radiative recombination into a benefit by using lateral oxidation to create current confinement barriers. The oxidation process, which initially might be seen as degrading the semiconductor material, is instead utilized to form high-resistivity regions that prevent current from reaching lossy surface areas, thereby eliminating non-radiative recombination pathways.
3Use of energy by moving object
If LED size is increased to decrease current density, then efficiency improves but device complexity and integration difficulty increase
Solution Approach 1:
The patent applies parameter changes by modifying the electrical resistance parameter of the cladding layer through lateral oxidation. This creates a high-resistivity current confinement barrier that enables efficient current distribution in smaller LED devices, allowing miniaturization without sacrificing efficiency or increasing integration complexity.
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 enhances internal quantum efficiency and luminous efficacy by confining current internally, reducing non-radiative recombination at external surfaces, allowing operation at lower currents and densities below standard LED conditions, thereby improving light emission efficiency.
Implementation Method 1
a first current spreading layer pillar is doped with a first dopant type and the second current spreading layer is doped with a second dopant type opposite the first dopant type
Implementation Method 2
an active layer between a first current spreading layer pillar and a second current spreading layer
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Methods and structures for forming arrays of LED devices are disclosed. The LED devices in accordance with embodiments of the invention may include an internally confined current injection area to reduce non-radiative recombination due to edge effects. Several manners for confining current may include etch removal of a current distribution layer, etch removal of a current distribution layer and active layer followed by mesa re-growth, isolation by ion implant or diffusion, quantum well intermixing, and oxide isolation.