Nitride Interlayer for Light Extraction in Patterned Substrate LEDs
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Solution Overview
Problem
Nitride-based light emitting diodes (LEDs) grown on patterned substrates face performance degradation due to the lack of a nitride interlayer, which hampers light extraction efficiency and output power compared to conventional non-patterned substrates.
Innovation Solution
Incorporating a nitride interlayer with alternating layers of indium and gallium nitride (InxGa1-xN) below or above the active region of the LED, along with a transparent conducting oxide (TCO) and a tunnel junction layer, to enhance light extraction and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If nitride-based LEDs are grown on patterned substrates without a nitride interlayer, then the device structure is simpler, but light extraction efficiency and output power are degraded
Solution Approach 1:
A nitride interlayer is introduced as an intermediary component between the patterned substrate and the active region. This interlayer mediates the optical interaction by reducing internal reflections and improving light extraction efficiency, thereby resolving the contradiction between structural simplicity and optical performance.
Solution Approach 2:
The nitride interlayer is constructed as a composite structure with alternating layers of indium gallium nitride (InGaN) and gallium nitride (GaN). This composite material design enables tailored optical properties that enhance light extraction while maintaining structural integrity, addressing the power output issue without excessive complexity.
2Ease of manufacture
If nitride-based LEDs are grown on patterned substrates without a nitride interlayer, then the manufacturing process is simpler, but light extraction efficiency is hampered
Solution Approach 1:
The nitride interlayer serves as an intermediary that optimizes the optical interface between the substrate and active region. By introducing this intermediate layer, light extraction efficiency is improved without requiring fundamental changes to the manufacturing process, thus maintaining ease of manufacture while reducing energy loss.
Solution Approach 2:
The interlayer modifies key optical parameters including refractive index matching and reflection coefficients. By changing these parameters through the alternating InGaN/GaN structure, light extraction efficiency is enhanced while the manufacturing process remains compatible with existing epitaxial growth techniques.
3Loss of energy
If a nitride interlayer with alternating InGaN and GaN layers is added, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The alternating InGaN/GaN layers create periodic variations in refractive index and bandgap energy. These parameter changes enable enhanced light extraction through constructive interference effects and reduced internal reflections, achieving improved optical performance with a relatively straightforward layered structure.
Solution Approach 2:
The nitride interlayer employs a composite material approach using alternating layers of InGaN and GaN. This composite structure leverages the complementary properties of each material to optimize optical performance while maintaining a manageable structural complexity that can be fabricated using standard epitaxial processes.
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
Significantly improves light extraction efficiency and output power of nitride LEDs on patterned substrates by acting as a buffer layer and reducing internal reflections, leading to enhanced performance and expanded commercial applications.
Implementation Method 1
enhance light extraction efficiency and output power
Implementation Method 2
reducing internal reflections
Implementation Method 3
transparent conducting oxide (TCO)
Implementation Method 4
nitride based active region... including at least one quantum well structure
Data Source
AI summary
A nitride light emitting diode, on a patterned substrate, comprising a nitride interlayer having at least two periods of alternating layers of InxGa1-xN and InyGa1-yN where 0<x<1 and 0≦y<1, and a nitride based active region having at least one quantum well structure on the nitride interlayer.