LED with Roughened Active Layer and Conformal Cladding
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Solution Overview
Problem
Conventional LEDs suffer from low light extraction efficiency due to internal reflections at the boundaries between the active layer and cladding layers, leading to significant light trapping and absorption, which limits their conversion efficiency and increases the number of LEDs required for high-power applications.
Innovation Solution
The introduction of pits in the n-cladding layer, which are strategically located on dislocations and have dimensions greater than the wavelength of light, helps redirect trapped light to escape through the transparent electrode or substrate, improving light extraction efficiency without the need for surface roughening, thus reducing the number of LEDs needed and fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional planar boundaries are used in LED structure, then manufacturing is simple, but light extraction efficiency is low due to internal reflections and trapping
Solution Approach 1:
The patent introduces curved interfaces between layers by forming the second layer to have a curved lower surface that conforms to a curved upper surface of the first layer. This curvature modifies the optical paths of light rays, reducing total internal reflection and improving light extraction efficiency compared to conventional planar boundaries.
Solution Approach 2:
The patent transitions from two-dimensional planar interfaces to three-dimensional curved interfaces. The curved surfaces introduce additional spatial dimensions for light manipulation, allowing light rays to escape at angles that would otherwise be trapped by planar boundaries, thereby improving extraction efficiency.
2Power
If multiple LEDs are used to achieve high power levels, then power requirements are met, but cost increases significantly
Solution Approach 1:
The patent changes the optical parameters of the LED structure by introducing curved interfaces and optimizing layer thicknesses and refractive indices. These parameter changes improve the conversion efficiency of individual LEDs, allowing fewer LEDs to achieve the same total power output, thereby reducing the quantity of LEDs needed.
3Ease of manufacture
If conventional LED structure is used, then heat dissipation requirements are high, but conversion efficiency is limited
Solution Approach 1:
The patent optimizes structural parameters including layer thicknesses, refractive indices, and interface curvatures to maximize light extraction efficiency. By improving conversion efficiency, less electrical power is converted to heat, reducing the thermal management requirements and associated manufacturing costs.
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 enhances light extraction efficiency by redirecting trapped light, reducing absorption, and lowering the operational cost of LEDs, while maintaining uniform current spreading and reflectivity, thereby increasing the maximum light output per LED.
Implementation Method 1
the active layer generating light characterized by a wavelength when holes and electrons recombine therein
Implementation Method 2
The introduction of pits in the n-cladding layer, which are strategically located on dislocations and have dimensions greater than the wavelength of light, helps redirect trapped light to escape through the transparent electrode or substrate
Data Source
AI summary
A light emitting device and method for making the same are disclosed. The device includes an active layer disposed between first and second layers. The first layer has top and bottom surfaces. The top surface includes a first material of a first conductivity type, including a plurality of pits in the substantially planar surface. The active layer overlies the top surface of the first layer and conforms to the top surface, the active layer generating light characterized by a wavelength when holes and electrons recombine therein. The second layer includes a second material of a second conductivity type, the second layer overlying the active layer and conforming to the active layer. The device can be constructed on a substrate having a lattice constant sufficiently different from that of the first material to give rise to dislocations in the first layer that are used to form the pits.