Deep UV LED with PLOG Buffer for Thermal and Defect Management
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Solution Overview
Problem
Current deep UV light-emitting diodes face challenges due to high dislocation densities and poor thermal conductivity, leading to limited output power and short device lifetimes, especially when using sapphire substrates, which restrict their commercial applications.
Innovation Solution
The development of a deep ultraviolet light-emitting structure with an AlxInyGa1-x-yN quantum-well active region on a template with a pulsed lateral overgrowth (PLOG) technique, using a substrate with etched pillars and multiple III-Nitride buffer layers for reduced defect density and enhanced thermal impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sapphire substrates are used for deep UV LEDs, then device fabrication is enabled, but thermal conductivity is poor leading to limited output power and short device lifetimes
Solution Approach 1:
The patent introduces a patterned buffer layer structure with etched pillars as an intermediary between the sapphire substrate and the active region. This mediator improves thermal conductivity while maintaining the benefits of sapphire substrate fabrication, thereby resolving the contradiction between output power and device lifetime
Solution Approach 2:
The buffer layer is segmented into a patterned structure with etched pillars rather than a continuous layer. This segmentation increases the effective thermal conductivity pathway while reducing defect density, enabling both higher output power and improved device lifetime
2Ease of manufacture
If conventional epitaxial growth is used on sapphire substrates, then device fabrication is achieved, but dislocation density remains high (10^8 to 10^10 cm^-2) reducing efficiency and lifetime
Solution Approach 1:
The patent applies preliminary patterning to the buffer layer before growing the active region. By etching pillars into the buffer layer first, the subsequent epitaxial growth occurs on a pre-prepared template that guides lateral overgrowth and filters dislocations, achieving low defect density while maintaining fabrication feasibility
Solution Approach 2:
The patent extracts or removes material from the buffer layer to create etched pillars. This removal creates a patterned structure that enables selective lateral overgrowth, effectively separating the growth pathways and filtering out dislocations to reduce defect density
3Manufacturing precision
If epitaxial lateral overgrowth (ELOG) is used to reduce dislocation density, then defect density decreases to 10^5 to 10^6 cm^-2, but aluminum-containing III-Nitride materials cannot be grown due to aluminum sticking to masked material
Solution Approach 1:
The patterned buffer layer with etched pillars serves as an intermediary structure that enables lateral overgrowth without requiring traditional masking. This intermediary approach allows aluminum-containing materials to be grown by providing defined growth pathways through the pillar structure, resolving the limitation of conventional ELOG
Solution Approach 2:
The patent transitions from planar masking-based lateral overgrowth to three-dimensional pillar-based selective growth. By etching pillars into the buffer layer, growth occurs in a controlled three-dimensional space around the pillars, enabling aluminum-containing materials to be deposited without sticking to masked surfaces
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 results in a significant reduction in dislocation density and improved thermal conductivity, enhancing the output power and lifetime of deep UV LEDs beyond previous state-of-the-art values, making them more suitable for commercial applications.
Implementation Method 1
a pulsed lateral overgrowth (PLOG) technique, using a substrate with etched pillars and multiple III-Nitride buffer layers for reduced defect density
Implementation Method 2
template with a pulsed lateral overgrowth (PLOG) technique, using a substrate with etched pillars
Data Source
AI summary
An ultra-violet emitting light-emitting device and method for fabricating an ultraviolet light emitting device (LED) with an AlInGaN multiple-quantum-well active region exhibiting stable cw-powers. The LED includes a template with an ultraviolet light-emitting structure on it. The template includes a first buffer layer on a substrate, then a second buffer layer on the first preferably with a strain-relieving layer in both buffer layers. Next there is a semiconductor layer having a first type of conductivity followed by a layer providing a quantum-well region with an emission spectrum ranging from 190 nm to 369 nm. Another semiconductor layer having a second type of conductivity is applied next. Two metal contacts are applied to this construction, one to the semiconductor layer having the first type of conductivity and the other to the semiconductor layer having the second type of conductivity, to complete the LED.