AlGaN UV LED Epitaxial Structure for Low-Absorption Light Extraction
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Solution Overview
Problem
Ultraviolet (UV) light emitting diodes (LEDs) with emission wavelengths less than 300 nanometers suffer from low efficiency due to absorption of UV light by p-type gallium nitride materials, limiting their applications in fields such as surface disinfection and biochemistry, and require a new p-type layer structure that enhances UV transmittance and conductivity.
Innovation Solution
A light emitting diode epitaxial structure (LEDES) based on aluminum gallium nitride (AlGaN) material is developed, featuring a structure with a buffer layer, n-type AlGaN layers, and a p-type AlGaN layer, along with a coarsened surface structure formed through etching or lithography processes to enhance light extraction, disrupting waveguide transmission and promoting UV light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If p-type GaN material is used in UV LED structure, then electrical conductivity is improved, but UV light absorption increases causing low external quantum efficiency
Solution Approach 1:
The patent extracts the problematic p-type GaN layer from the LED structure and replaces it with a p-type AlGaN layer having higher aluminum content (x>0.3). This extraction removes the UV-absorbing component while maintaining hole injection functionality through the modified p-type layer.
Solution Approach 2:
The patent changes the compositional parameter of the p-type layer by increasing aluminum content from traditional low-Al compositions to high-Al compositions (x>0.3). This parameter change shifts the material's optical properties to become transparent to UV wavelengths while preserving electrical conductivity through optimized doping.
2Loss of energy
If high aluminum content AlGaN material is used, then UV light transmittance is improved, but hole concentration and conductivity become insufficient
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: aluminum composition ratio (x>0.3), doping concentration (1×10^18 to 1×10^20 atoms/cm³), and layer thickness (50-200 nm). These coordinated parameter changes achieve the balance between UV transparency and hole concentration by selecting specific ranges for each parameter.
Solution Approach 2:
The patent creates a composite structure combining p-type AlGaN with specific aluminum content with other layers including n-type AlGaN and active regions. This composite approach allows different layers to optimize for their specific functions: UV transparency in the p-type layer and carrier injection in doped regions.
3Ease of manufacture
If traditional pn structure is used in UV LED, then manufacturing simplicity is maintained, but light extraction efficiency remains low
Solution Approach 1:
The patent segments the traditional simple pn structure into multiple functional layers: buffer layer, n-type AlGaN layer, active region, p-type AlGaN layer, and electron blocking layer. This segmentation allows each layer to be optimized for its specific function while maintaining overall structural simplicity in the manufacturing process.
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 LEDES increases the external quantum efficiency and optical power output of UV LEDs by effectively extracting UV light absorbed in traditional LEDs, reducing heating effects and improving light extraction efficiency.
Implementation Method 1
a coarsened surface structure formed through etching or lithography processes to enhance light extraction, disrupting waveguide transmission
Implementation Method 2
a coarsened surface structure formed through etching or lithography processes to enhance light extraction, disrupting waveguide transmission
Data Source
AI summary
A light emitting diode epitaxial structure (LEDES) based on an aluminum gallium nitride material and a manufacturing method thereof are described. The LEDES includes a first layer of n-type aluminum gallium nitride, an active layer comprising aluminum gallium nitride, a p-type aluminum gallium nitride, and a second layer of n-type aluminum gallium nitride disposed above the p-type aluminum gallium nitride along an epitaxial growth direction. An epitaxial layer comprising a gallium nitride layer is contained between an epitaxial layer of the p-type aluminum gallium nitride and an epitaxial layer of the second layer of n-type aluminum gallium nitride. The epitaxial layer comprising the gallium nitride layer has an energy band width smaller than those of the epitaxial layers of the p-type aluminum gallium nitride and the second layer of n-type aluminum gallium nitride. A coarsened structure exists on a surface of the second layer of n-type aluminum gallium nitride.