UV LED Structure with Recessed Reflective Layer for Efficiency
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Solution Overview
Problem
Ultraviolet light-emitting diodes (UV LEDs) with short wavelengths face issues such as higher voltage, electron overflow, poor hole injection efficiency, and reduced luminous efficiency due to the use of aluminum gallium nitride, which affects their light extraction efficiency.
Innovation Solution
A light-emitting diode structure is designed with a first type semiconductor layer, a light-emitting layer, a second type semiconductor layer, a reflective layer, and an ohmic contact layer, where the second type semiconductor layer features recesses or protrusions to accommodate the reflective layer, enhancing light extraction through distributed Bragg reflectors and improved electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If aluminum gallium nitride is used as the material for ultraviolet light-emitting diode with short wavelength, then the emission wavelength can be achieved, but the voltage increases and luminous efficiency deteriorates
Solution Approach 1:
The second type semiconductor layer is divided into multiple regions with different depths (recesses and protruding portions), creating localized segments that can independently manage light extraction and electrical injection. This segmentation allows optimization of different areas for different functions, reducing overall voltage while improving luminous efficiency.
Solution Approach 2:
Different regions of the second type semiconductor layer are given different local qualities: recesses are designed for enhanced light extraction with reflective layers, while protruding portions are optimized for electrical contact. This local differentiation allows each region to perform its specific function optimally without compromising the other.
2Reliability
If aluminum gallium nitride is used as the material for ultraviolet light-emitting diode with short wavelength, then the emission wavelength can be achieved, but electron overflow and poor hole injection efficiency occur
Solution Approach 1:
The semiconductor layer is segmented into recesses and protruding portions that spatially separate electron and hole management functions. This segmentation prevents electron overflow by confining electrons in specific regions while ensuring efficient hole injection in other regions.
Solution Approach 2:
The reflective layer acts as an intermediary in the recesses, mediating between the semiconductor material and the light extraction process. It helps manage carrier distribution and prevents electron overflow while facilitating hole injection through the structured interface.
3Illumination intensity
If a reflective layer is added to improve light extraction efficiency, then luminous efficiency improves, but device complexity increases
Solution Approach 1:
The reflective layer is applied only in specific recessed regions rather than uniformly across the entire surface. This segmented application reduces the total amount of reflective material needed and simplifies the manufacturing process while still achieving significant light extraction improvement.
Solution Approach 2:
Instead of adding complexity in the planar dimension, the solution introduces vertical dimensionality through recesses and protruding portions. This dimensional change allows the reflective layer to be strategically positioned where it provides maximum benefit without uniformly increasing device 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
The structure significantly improves the luminous efficiency or light extraction efficiency of UV LEDs with short wavelengths by effectively managing light emission and electrical contacts, addressing the previous efficiency issues.
Implementation Method 1
The reflective layer is disposed in the recesses
Implementation Method 2
enhancing light extraction through distributed Bragg reflectors
Data Source
AI summary
A light-emitting diode structure includes a first type semiconductor layer, a light-emitting layer, a second type semiconductor layer, a reflective layer, and an ohmic contact layer. The light-emitting layer is disposed under the first type semiconductor layer. The second type semiconductor layer is disposed under the light-emitting layer, wherein the second type semiconductor layer includes a plurality of recesses which are recessed from a lower surface of the second type semiconductor layer toward the light-emitting layer. The reflective layer is disposed in the recesses. The ohmic contact layer is disposed under the lower surface of the second type semiconductor layer and surrounds the recesses. The light-emitting diode structure can increase the luminous efficiency greatly.