Ultraviolet Emitters

UV LED Technology

AlGaN-based light emitting diodes for deep ultraviolet applications

Deep UV Semiconductor Light Sources

Aluminum Gallium Nitride (AlGaN) based ultraviolet light emitting diodes represent a transformative technology enabling compact, mercury-free UV light sources. By adjusting the aluminum composition in the active region, emission wavelengths can be tuned from 210nm to 365nm, covering the entire UV-A, UV-B, and UV-C spectral ranges.

UV-C LEDs emitting at 260-280nm are particularly significant for disinfection applications, as this wavelength range corresponds to peak DNA absorption. The COVID-19 pandemic accelerated commercialization of UV-C LED systems for air and surface sterilization.

UV Spectral Regions

UV-C 200-280 nm Germicidal

UV-B 280-315 nm Medical

UV-A 315-400 nm Curing

Device Structure & Materials

Deep UV LED Structure

p-Contact (Ni/Au)

p-AlGaN (60-70% Al)

Electron Blocking Layer

Active Region (AlGaN MQW)

n-AlGaN (60-70% Al)

AlN Buffer Layer

Substrate (AlN/Sapphire)

AlGaN Heterostructures

Deep UV LEDs utilize high aluminum content AlGaN alloys for both the active region and cladding layers. The aluminum composition determines the bandgap energy and thus emission wavelength according to Vegard's law, with higher Al content producing shorter wavelengths.

Critical Design Aspects

Al composition 50-100% for UV-C emission
AlN substrates for reduced defect density
Multiple quantum well active region (3-5 wells)
Electron blocking layer to prevent carrier leakage
Transparent contact layers for light extraction
Surface texturing and encapsulation for efficiency

External Quantum Efficiency Challenges

UV-C LED efficiency remains significantly lower than visible LEDs due to fundamental materials challenges. Current state-of-the-art devices achieve 10-20% wall-plug efficiency, compared to 60-80% for blue LEDs.

Low p-type Conductivity

High Mg acceptor activation energy in high-Al AlGaN limits hole concentration. Room temperature hole density <10^17 cm^-3 causes high series resistance and current crowding.

Poor Light Extraction

High refractive index contrast (n≈2.5) leads to total internal reflection. Only 4-8% of photons escape without surface texturing or photonic crystal structures.

Threading Dislocations

Lattice mismatch between AlN and sapphire substrates creates threading dislocation densities >10^9 cm^-2, acting as non-radiative recombination centers.

Transparent Contacts

Conventional metal contacts absorb UV-C light. Transparent conductive oxides and tunnel junctions are required but challenging to implement with low resistance.

Applications & Markets

UV-C LEDs at 265-275nm provide peak germicidal effectiveness by damaging DNA/RNA of bacteria, viruses, and pathogens. Applications include water purification, air sterilization, and surface disinfection in healthcare and consumer products.

99.9% Pathogen reduction

10-30 mJ/cm² Typical dose

Instant on No warm-up time

UV-A LEDs polymerize photoreactive resins and inks for printing, coatings, and adhesives. High-power LED arrays (>10W) enable rapid curing with precise spatial and temporal control, eliminating mercury lamp hazards.

Instant on/off Cool cure Long lifetime Compact design

UV absorption spectroscopy at 254nm enables detection of aromatics, nitrates, and organic compounds in water quality monitoring and process control. LED-based sensors offer portable, real-time analysis capability.

Real-time analysis Portable Low power Maintenance-free

Narrow-band UV-B (311nm) phototherapy treats psoriasis, vitiligo, and eczema. LED systems provide targeted treatment with precise dose control and reduced erythema compared to broadband UV sources.

Targeted therapy Dose control Home treatment Reduced side effects

UV-A excites fluorescence of biological fluids, document security features, and mineral samples. Portable LED flashlights enable field investigation and authentication of currency, IDs, and artwork.

Fluorescence excitation Document verification Crime scene investigation Mineral identification

Supplemental UV lighting enhances secondary metabolite production, improves plant immunity, and regulates morphology. LED grow lights incorporate UV-A (380-400nm) for quality enhancement in controlled agriculture.

Metabolite boost Disease resistance Compact growth Quality enhancement

Research & Development

AlN Substrate Technology

Bulk AlN substrates grown by physical vapor transport (PVT) reduce threading dislocation density by 2-3 orders of magnitude compared to sapphire. Single-crystal AlN enables >50% improvement in UV-C LED efficiency.

Tunnel Junction Integration

Heavily-doped GaN/AlGaN tunnel junctions enable transparent p-contact by current flow through n-type layer. Eliminates UV absorption by metal p-contacts, improving light extraction by 50-100%.

Photonic Crystal LEDs

Nanopatterned photonic crystal structures on LED surface reduce total internal reflection and enhance light extraction. 2D photonic lattices improve extraction efficiency from 8% to 20-30% for UV-C devices.

Quantum Well Optimization

Polarization engineering through quantum well design modifies valence band structure to enhance transverse electric (TE) mode emission. Improves light extraction in flip-chip geometry by 2x.

High-Power Arrays

Development of >1W/mm² power density UV-C LED arrays requires advanced thermal management including diamond heat spreaders and microchannel cooling for industrial-scale disinfection systems.

Alternative Buffer Layers

Compositionally-graded AlGaN buffer layers and superlattice structures reduce strain and defect propagation from substrate. Enables growth on cost-effective sapphire with improved material quality.

Market Outlook

$1.3B 2024 Market Size

35% Annual Growth (CAGR)

$5.6B 2030 Projection

The UV LED market is experiencing rapid growth driven by disinfection applications, regulatory phase-out of mercury lamps, and cost reductions from manufacturing scale-up. UV-C LEDs represent the fastest-growing segment with 40%+ annual growth.

Key market drivers include water/air purification demand, adoption in consumer electronics (smartphone sterilizers), and automotive interior disinfection systems. Industrial UV curing remains the largest application segment by revenue.

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