AlGaN Pre-Barrier Layer Sequence for LED Crack Resistance
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Solution Overview
Problem
Semiconductor layer sequences for light-emitting diodes in the UVA spectral range face issues with crack formation due to high aluminum content, leading to quality problems and non-uniform charge carrier distribution, while low aluminum content results in increased non-radiative losses at high current densities and temperatures.
Innovation Solution
A semiconductor layer sequence with a pre-barrier layer and pre-quantum well having higher aluminum content and thickness, and main barrier layers with lower aluminum content and thickness, along with a multi-quantum well structure designed to optimize charge carrier distribution and reduce leakage currents, is employed. This sequence includes a pre-barrier layer, pre-quantum well, multi-quantum well structure, electron-blocking layer, and post-barrier layer, with specific compositions and thicknesses to manage piezoelectric fields and transition energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high aluminum content is used in barrier layers, then charge carrier confinement is improved, but crack formation occurs due to tensile stress
Solution Approach 1:
The barrier layer is segmented into two distinct layers: a pre-barrier layer with high aluminum content (20-30%) for strong charge carrier confinement, and a main barrier layer with lower aluminum content (10-20%) to reduce tensile stress and prevent cracks. This segmentation allows each layer to optimize its aluminum content for its specific function without compromising the other.
Solution Approach 2:
Different regions of the barrier structure are assigned different aluminum contents tailored to their specific requirements. The pre-barrier layer adjacent to the quantum well has high aluminum content for effective carrier confinement, while the main barrier layer has reduced aluminum content to minimize stress and prevent cracking, creating a spatially optimized structure.
2Strength
If low aluminum content is used in barrier layers, then crack formation is reduced, but non-radiative losses increase at high current densities
Solution Approach 1:
The barrier structure is divided into two layers with different aluminum contents: the pre-barrier layer with higher aluminum content (20-30%) prevents excessive non-radiative losses by maintaining adequate charge carrier confinement, while the main barrier layer with lower aluminum content (10-20%) reduces tensile stress to prevent cracks.
Solution Approach 2:
The pre-barrier layer positioned close to the quantum well maintains higher aluminum content to ensure effective charge carrier confinement and minimize non-radiative recombination, while the main barrier layer further from the quantum well has reduced aluminum content to reduce stress, creating a spatially optimized solution.
3Reliability
If high aluminum content is used, then barrier height is increased, but piezoelectric fields become non-uniform causing charge carrier distribution issues
Solution Approach 1:
The barrier layer is segmented into a pre-barrier layer and a main barrier layer with different aluminum contents. The pre-barrier layer has higher aluminum content for adequate barrier height, while the main barrier layer has lower aluminum content to reduce piezoelectric field non-uniformity, allowing both requirements to be satisfied in different regions.
Solution Approach 2:
Different aluminum contents are assigned to different regions of the barrier structure: the pre-barrier layer adjacent to the quantum well has higher aluminum content for sufficient barrier height, while the main barrier layer has lower aluminum content to reduce piezoelectric field effects, creating a spatially optimized charge carrier distribution.
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 solution achieves improved crystal quality, reduced non-radiative losses, and enhanced temperature stability by optimizing charge carrier distribution and preventing leakage currents, while maintaining high efficiency and adaptability to desired emission wavelengths.
Implementation Method 1
manage piezoelectric fields and transition energies
Implementation Method 2
The main quantum wells are designed to generate a radiation having a wavelength of maximum intensity of at least 365 nm or 375 nm or 385 nm and/or of at most 490 nm or 410 nm or 395 nm
Data Source
AI summary
In an embodiment a semiconductor layer sequence includes a pre-barrier layer including AlGaN, a pre-quantum well including InGaN having a first band gap, a multi-quantum well structure including a plurality of alternating main quantum wells of InGaN having a second band gap and main barrier layers of AlGaN or AlInGaN, wherein the second band gap is smaller than the first band gap and the main quantum wells are configured to generate a radiation having a wavelength of maximum intensity between 365 nm and 490 nm inclusive, a post-quantum well with a third band gap which is larger than the second band gap, a post-barrier layer including AlGaN or AlInGaN and an electron-blocking layer including AlGaN.