GaN LED Light Extraction via N-Face Scattering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LEDs have low light conversion efficiency due to significant light loss as generated light is trapped between the top layer and the substrate, with existing techniques to improve light extraction being costly and difficult to control, such as creating a rough surface using etching which is challenging for GaN-based LEDs on sapphire substrates.
Innovation Solution
The introduction of a light scattering layer with a GaN crystalline layer having an N-face surface, which is etched to create features that scatter light, flipping the crystal orientation during growth to expose the N-face for easier etching and improving light extraction efficiency without the need for costly lithographic masking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rough surface is created on the top layer to improve light extraction, then light extraction efficiency is improved, but manufacturing cost and complexity increase due to required lithographic masking operations
Solution Approach 1:
The patent changes the crystal orientation parameter of the top layer from conventional Ga-face to N-face. This parameter change enables the surface to be etched without requiring lithographic masking operations, thereby reducing fabrication complexity while still achieving the rough surface needed for improved light extraction efficiency
Solution Approach 2:
Instead of etching the conventional Ga-face surface, the patent inverts the approach by exposing the N-face surface which has opposite etching properties. This inversion allows for simpler etching processes that do not require complex lithographic masking, thus reducing device complexity while maintaining energy efficiency improvements
2Loss of energy
If etching is performed on GaN-based LEDs on sapphire substrates to create a rough surface, then light extraction is improved, but etching difficulty and process control become significant problems
Solution Approach 1:
The patent changes the crystal orientation parameter from Ga-face to N-face, which fundamentally alters the etching characteristics. The N-face surface exhibits much better etching properties, allowing for easier and more controllable etching processes that can create the necessary rough surface features for improved light extraction
3Power
If multiple LEDs are used to achieve high power levels, then power output is improved, but cost increases due to the need for multiple individual LEDs
Solution Approach 1:
By changing the crystal orientation parameter to N-face and implementing the associated etching improvements, the patent significantly enhances light extraction efficiency. This allows individual LEDs to operate at higher effective power levels, reducing the quantity of LEDs needed to achieve high power output
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 scattering light that would otherwise be trapped, reducing the number of LEDs required for a given light source and lowering operational costs by increasing the conversion efficiency of individual LEDs.
Implementation Method 1
The N-face surface includes features that scatter light of the predetermined wavelength
Implementation Method 2
the active layer emitting light of a predetermined wavelength when electrons and holes from the n-type GaN layer and the p-type GaN layer, respectively, combine therein
Implementation Method 3
Light that strikes the boundary at angles that are greater than the critical angle is totally reflected at the boundary
Data Source
AI summary
A light-emitting device and the method for making the same are disclosed. The device includes a substrate, a light-emitting structure and a light scattering layer. The light-emitting structure includes an active layer sandwiched between a p-type GaN layer and an n-type GaN layer, the active layer emitting light of a predetermined wavelength when electrons and holes from the n-type GaN layer and the p-type GaN layer, respectively, combine therein. The light scattering layer includes a GaN crystalline layer characterized by an N-face surface. The N-face surface includes features that scatter light of the predetermined wavelength. The light-emitting structure is between the N-face surface and the substrate.