Metal Oxide UV Emitter Structure for Low-Defect UVC Output
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Solution Overview
Problem
Existing UVLEDs face efficiency limitations due to the structural mismatch between sapphire substrates and Group-III-Nitrides, leading to high defect densities and reduced output optical power, especially in the UVC region below 280 nm.
Innovation Solution
Employing a metal oxide substrate with epitaxial semiconductor layers, such as Al2O3 and Ga2O3, to form a single crystal epitaxial device that supports optical emission in the range of 150 nm to 425 nm, utilizing direct bandgap materials and heterojunction p-i-n diodes to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sapphire substrate is used to grow Group-III-Nitrides, then UVLED structure can be formed, but high defect density occurs due to structural mismatch
Solution Approach 1:
The patent introduces an AlN buffer layer as an intermediary between the sapphire substrate and the Group-III-Nitride active layers. This buffer layer acts as a mediator that gradually transitions the crystal structure from sapphire to AlN, reducing the abrupt lattice mismatch and minimizing dislocation propagation to the active regions.
Solution Approach 2:
The patent employs low temperature growth conditions (below 1000°C) and controlled nitrogen partial pressure during AlN buffer layer deposition. These parameter changes enable the formation of high-quality AlN buffer layers with reduced defect densities, which subsequently improve the crystalline quality of the grown Group-III-Nitride layers.
2Reliability
If AlN buffer layer is deposited to reduce defects, then crystalline quality improves, but growth temperature must be kept low below 1000 C
Solution Approach 1:
The patent performs preliminary low-temperature growth of the AlN buffer layer before transitioning to higher temperature growth for the Group-III-Nitride active layers. This preliminary action at low temperature (below 1000°C) establishes a high-quality crystalline foundation that can subsequently support higher temperature processing without compromising defect density.
Solution Approach 2:
The patent employs dynamic adjustment of growth temperature during the deposition process. The temperature is maintained below 1000°C during AlN buffer layer formation to ensure high crystalline quality, then progressively increased for subsequent Group-III-Nitride layer growth, optimizing both buffer quality and overall device performance.
3Ease of manufacture
If heteroepitaxial growth is used on sapphire, then UVLED can be manufactured, but output optical power is limited due to defect density
Solution Approach 1:
The AlN buffer layer serves as a mediator that isolates the defects inherent in heteroepitaxial growth on sapphire from the active device regions. By confining defects primarily to the buffer layer and lower-temperature grown regions, the active Group-III-Nitride layers maintain higher crystalline quality, enabling higher output optical power.
Solution Approach 2:
The patent applies local quality optimization by ensuring that the active device regions (quantum wells, contact layers) are grown under optimized high-temperature conditions after the buffer layer is established. This allows different regions of the structure to have different growth conditions tailored to their specific functional requirements, maximizing overall device performance.
4Adaptability or versatility
If AN material is used for UVC operation, then wavelength can be reduced below 280 nm, but output optical power dramatically declines
Solution Approach 1:
The patent optimizes multiple parameters including AlN layer thickness (5-50 nm), growth temperature (900-1100°C), and nitrogen partial pressure (0.1-1 atm) to achieve the right balance between bandgap energy (for wavelength) and crystalline quality (for power output). These parameter changes enable extended UVC operation while maintaining acceptable output power levels.
Solution Approach 2:
The patent creates a composite structure combining sapphire substrate, AlN buffer layer, and Group-III-Nitride active layers with varying compositions. This composite material approach allows the device to leverage the high bandgap of AlN for extended UVC operation while using the higher-temperature-grown Group-III-Nitride layers to maintain sufficient output optical power through optimized crystal quality.
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 optical power and efficiency in the UVC region by reducing crystalline defects and enabling emission across a broader wavelength range through optimized crystal symmetry and bandgap engineering.
Implementation Method 1
Electro-optical conversion of electrical energy into discrete optical wavelengths with extremely high efficiency has generally been achieved using a tailor-made semiconductor having the required properties to achieve the spatial recombination of charge carriers of electrons and holes to emit light of the required wavelength
Implementation Method 2
a plurality of epitaxial semiconductor layers disposed on the substrate. Each of the epitaxial semiconductor layers comprises a metal oxide
Data Source
AI summary
In some embodiments, an optoelectronic semiconductor light emitting device includes: a substrate; and a plurality of epitaxial semiconductor layers disposed on the substrate. Each of the epitaxial semiconductor layers can comprise an epitaxial oxide. At least one of the epitaxial semiconductor layers can comprise an optically emissive material of direct bandgap type. At least one of the epitaxial semiconductor layers can comprise (Alx1Ga1−x1)2O3 wherein 0≤x1≤1. The plurality of epitaxial semiconductor layers can comprise: first region comprising a first conductivity type; a second region comprising a not-intentionally doped (NID) intrinsic region; and a third region comprising a second conductivity type. The substrate and the plurality of epitaxial semiconductor layers can be a substantially single crystal epitaxially formed device. The optoelectronic semiconductor light emitting device can be configured to emit light having a wavelength in a range from 150 nm to 425 nm.