Flip-Chip UV Light Emitter With Interference-Tuned Gradient Layer
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Solution Overview
Problem
Existing light emitting devices using Group III nitride semiconductors for ultraviolet light emission face challenges in maximizing axial intensity while maintaining low drive voltage, as they often suffer from inefficient light extraction and increased series resistance due to the thickness-dependent semiconductor layers.
Innovation Solution
A flip-chip type light emitting device with a specific configuration including an n-type layer, active layer, electron blocking layer, composition gradient layer, and p-type contact layer, where the composition gradient layer's thickness is optimized to enhance interference and direct light perpendicular to the main surface, using a sealing portion and lens with controlled refractive indices to improve light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the semiconductor layer is increased to improve light extraction efficiency, then axial intensity increases, but series resistance increases causing drive voltage to increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the semiconductor layer to satisfy the interference condition n×d=m×λ/2, where d is the thickness, n is the refractive index, λ is the emission wavelength, and m is an integer. This optimization allows constructive interference of light waves to enhance axial intensity while maintaining appropriate series resistance levels, thus resolving the contradiction between light extraction efficiency and drive voltage.
2Productivity
If the semiconductor layer thickness is optimized for light extraction, then light extraction efficiency improves, but series resistance becomes thickness-dependent causing drive voltage changes
Solution Approach 1:
The patent optimizes the semiconductor layer thickness as a critical parameter to satisfy the interference condition, which simultaneously improves light extraction efficiency and controls series resistance. By treating thickness as the key design parameter that affects both optical and electrical properties, the patent resolves the complexity of managing both light extraction and series resistance independently.
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 effectively increases axial intensity while minimizing the increase in drive voltage by controlling light interference and optimizing light extraction, enhancing the overall performance of the light emitting device.
Implementation Method 1
a thickness of the composition gradient layer is set such that light directed from the active layer toward the n-type layer and light directed from the active layer toward a side opposite to the n-type layer and then reflected by the p-side electrode toward the n-type layer strengthen each other in a direction perpendicular to a main surface of the light emitting element due to interference
Implementation Method 2
a sealing portion in contact with and covering at least an upper surface of the light emitting element and having a refractive index higher than a refractive index of air and lower than a refractive index of the light emitting element; and a lens in contact with and covering the sealing portion and having a refractive index higher than the refractive index of the sealing portion
Data Source
AI summary
A light emitting device includes: a flip-chip type light emitting element; a sealing portion; and a lens as defined herein, the light emitting element includes an n-type layer, an active layer, an electron blocking layer, a composition gradient layer, a p-type contact layer, and a p-side electrode as defined herein, and a thickness of the composition gradient layer is set such that light directed from the active layer toward the n-type layer and light directed from the active layer toward a side opposite to the n-type layer and then reflected by the p-side electrode toward the n-type layer strengthen each other in a direction perpendicular to a main surface of the light emitting element due to interference.