Internally Confined LED Current Injection for 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, as electrons and holes recombine non-radiatively at external surfaces, especially at higher current densities.
Innovation Solution
The development of LED devices with a confined current injection area, where a current spreading layer pillar is doped with a specific dopant type and surrounded by a cladding layer, allowing current confinement within the active layer, reducing lateral current spreading and non-radiative recombination, and enabling operation at lower current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current density is increased to improve luminance output, then brightness increases, but luminous efficacy decreases due to efficiency droop
Solution Approach 1:
The current spreading layer is segmented into a pillar structure with a central region and surrounding regions, creating distinct current injection zones. This segmentation allows current to be confined to specific areas, reducing lateral spreading and minimizing non-radiative recombination at external surfaces, thereby maintaining high luminous efficacy even at elevated luminance levels
Solution Approach 2:
Different regions of the LED structure are assigned different doping types and concentrations: the central region uses one dopant type while surrounding regions use opposite dopant types. This local quality variation creates electric field distributions that confine current injection to the central active area, reducing efficiency droop and improving luminous efficacy while maintaining required luminance output
2Loss of energy
If LED active layer area is increased to reduce current density, then efficiency droop is reduced, but device area increases
Solution Approach 1:
By creating localized regions with different doping characteristics within a compact structure, the invention achieves effective current density management without requiring large device areas. The doped and undoped regions work together to confine current injection, reducing efficiency droop in a small footprint
Solution Approach 2:
The invention transitions from a planar current spreading approach to a three-dimensional pillar structure with vertical doping gradients. This dimensional change allows current confinement through vertical electric fields and doping profiles, achieving efficient current management in a compact vertical structure rather than requiring lateral expansion
3Stability of the object's composition
If current spreading layer is made wider to improve current distribution, then current uniformity improves, but lateral current spreading increases causing non-radiative recombination
Solution Approach 1:
The current spreading layer is divided into a central pillar region and surrounding regions with different doping types. This segmentation creates vertical current confinement that improves current distribution uniformity in the active layer while preventing lateral spreading into non-radiative recombination zones at the edges
Solution Approach 2:
Undoped or oppositely doped surrounding regions act as intermediary barriers between the central current injection region and the external surfaces. These intermediary regions create electric field configurations that guide current vertically into the active layer while blocking lateral spreading, thus improving current uniformity without increasing non-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 configuration enhances internal quantum efficiency and luminous efficacy by confining current internally, reducing non-radiative recombination and increasing light emission efficiency, even at lower current densities, thus overcoming the efficiency droop phenomenon.
Implementation Method 1
The 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
As those defects become saturated radiative recombination dominates and efficiency increases
Implementation Method 3
electrons and holes recombine non-radiatively at external surfaces, especially at higher current densities
Data Source
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.