A5025052289- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Ga2O3 and related materials
- Semiconductor materials and devices
- Semiconductor Lasers and Optical Devices
- ZnO doping and properties
- Photonic and Optical Devices
- Metal and Thin Film Mechanics
- Photocathodes and Microchannel Plates
- Silicon Carbide Semiconductor Technologies
- Semiconductor materials and interfaces
- Solid State Laser Technologies
- Acoustic Wave Resonator Technologies
- Advanced Semiconductor Detectors and Materials
- Spectroscopy and Laser Applications
- Advancements in Semiconductor Devices and Circuit Design
- Thin-Film Transistor Technologies
- Optical Coatings and Gratings
- Plasma Diagnostics and Applications
- Quantum Dots Synthesis And Properties
- Organic Light-Emitting Diodes Research
- Advanced Fiber Laser Technologies
- Advanced Fiber Optic Sensors
- Laser Design and Applications
- Induction Heating and Inverter Technology
Ferdinand-Braun-Institut
2014-2024
Kirchhoff (Germany)
2010-2023
Forschungsverbund Berlin
2010
The field of AlGaInN ultraviolet UV light-emitting diodes (LEDs) is reviewed, with a summary the state-of-the-art in device performance and enumeration applications. Performance-limiting factors for high-efficiency LEDs are identified recent advances development deep emitters presented.
The polarization of the in-plane electroluminescence (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in ultraviolet-A and ultraviolet-B spectral range has been investigated. intensity for transverse-electric polarized relative to transverse-magnetic decreases with decreasing emission wavelength. This effect is attributed rearrangement valence bands at Γ-point Brillouin zone changing aluminum indium mole fractions wells. For shorter wavelength crystal-field split-off...
InGaN quantum wells were grown by metal organic vapor-phase epitaxy on polar (0 0 0 1), nonpolar (1 0 0) and semipolar (1 0 2), (1 1 2), (1 0 1) as well (2 0 1) oriented GaN substrates. The room-temperature photoluminescence (PL) electroluminescence (EL) emission energies for different crystal orientations show large variations of up to 600 meV. following order the energy was found throughout entire range growth temperatures: < (1 1 2) = (0 0 0 1) (1 0 2). In differentiate between...
The design and Mg-doping profile of AlN/Al0.7Ga0.3N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) below 250 nm was investigated. By inserting an AlN layer (EBL) into the EBH, we were able to increase emission power significantly reduce long wavelength parasitic luminescence. Furthermore, leakage suppressed by optimizing thickness EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low...
The performance characteristics of optically pumped laser heterostructures emitting in the UV-C spectral range between 272 and 279 nm are investigated. were grown by metal-organic vapor phase epitaxy on (0001) planar AlN/sapphire, epitaxially laterally overgrown (ELO) bulk AlN substrates with threading dislocation densities ranging from 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> to 10...
The optical polarization of emission from ultraviolet (UV) light emitting diodes (LEDs) based on (0001)-oriented AlxGa1−xN multiple quantum wells (MQWs) has been studied by simulations and electroluminescence measurements. With increasing aluminum mole fraction in the well x, in-plane intensity transverse-electric (TE) polarized decreases relative to that transverse-magnetic light, attributed a reordering valence bands AlxGa1−xN. Using k ⋅ p theoretical model calculations, AlGaN MQW active...
High temperature annealed AlN/sapphire templates exhibit a reduced in-plane lattice constant compared to conventional non-annealed grown by metalorganic vapor phase epitaxy (MOVPE). This leads additional mismatch between the template and AlGaN-based ultraviolet-C light emitting diode (UVC LED) heterostructure on these templates. introduces compressive strain in AlGaN quantum wells resulting enhanced transverse electric polarization of well emission at wavelengths below 235 nm layer...
Far-ultraviolet-C (far-UVC) light-emitting diodes (LEDs) with an emission wavelength of 234 nm different polarization-doped AlGaN hole injection layers (HILs) are compared regarding their power, voltage, and leakage current. The influence the thickness layer (PDL), additional Mg doping PDL, as well a combination PDL conventionally Mg-doped HIL will be discussed. thicknesses show nearly no on power or voltage. However, current LEDs below turn-on voltage decreases increasing PDL. In contrast,...
Normally-off GaN transistors for power applications in p-type gate technology with a modified carbon-doped buffer are presented. A combination of an AlGaN back-barrier the prevents early off-state punch-through. Simultaneously, on-state resistance could be kept low and threshold voltage 1.1 V high enough secure normally-off operation. 1000 breakdown strength has been obtained devices 6 μm gate-drain spacing. The resulting scaling slope is 170 V/μm distance. 7.4 Ωmm. <sub...
Silicon doping of AlxGa1−xN layers with high aluminum mole fractions (0.8 &lt; x 1) was studied. The AlGaN:Si were pseudomorphically grown by metalorganic vapor phase epitaxy on low defect density epitaxially laterally overgrown AlN/sapphire templates. effects SiH4/III ratio and content the resistivity, carrier concentration, mobility have been investigated. By variation during growth AlxGa1−xN:Si layers, a recorded resistivity Al0.81Ga0.19N:Si obtained 0.026 Ω cm. increases...
We report on the use of micro-LED arrays, consisting a matrix interconnected micrometer-size light-emitting diodes (LEDs), to ensure uniform current injection, reduced series resistance, and improved heat extraction in LEDs emitting ultraviolet wavelength region. With help experiments simulations, we show that, both 380- 300- 325-nm LEDs, greater than twofold decrease thermal resistance device, as compared with conventional large area contact, is possible arrays. The was found linearly size...
The impact of operation current on the degradation behavior 310 nm UV LEDs is investigated over 1000 h stress. It ranges from 50 to 300 mA and corresponds densities 34 201 A/cm2. To separate that temperature, junction temperature kept constant by adjusting heat sink temperature. Higher was found strongly accelerate optical power reduction during operation. A mathematical model for lifetime prediction introduced. indicates inversely proportional cube density, suggesting involvement Auger...
An extensive analysis of the degradation characteristics AlGaN-based ultraviolet light-emitting diodes emitting around 265 nm is presented. The optical power LEDs stressed at a constant dc current 100 mA (current density = 67 A/cm2 and heatsink temperature 20 °C) decreased to about 58% its initial value after 250 h operation. origin this effect has been studied using capacitance-voltage photocurrent spectroscopy measurements conducted before aging. overall device capacitance decreased, which...
In this paper, we will present the development of a compact LED-based optical gas sensing system in ultraviolet-C spectral region. This includes design LED heterostructure emitting near 226 nm, an chip, and implementation into capable detecting nitrogen oxide concentrations ppm range.
Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of different p-AlGaN short period superlattice (SPSL) cladding layers various are compared. heterostructures contain all elements that needed a current-injection including and waveguide as well an AlGaN quantum active region emitting near 270 nm. We found increasing content in the cladding, turn-on voltage increases, while...
We report on the degradation of electro-optical parameters (In)AlGaN-based ultraviolet-B light-emitting diodes (LEDs) stressed at a constant dc current 100 mA and simultaneous change in depth profile hydrogen (H) concentration during operation. The optical power LEDs decreased to ~45% its initial value after 10 h operation saturated for longer times. In addition, drive voltage dropped about first gradually increased following time. possible changes impurity distribution have been studied by...
Herein, the scope is to provide an overview on current status of AlN/sapphire templates for ultraviolet B (UVB) and C (UVC) light‐emitting diodes (LEDs) with focus work done previously. Furthermore, approaches improve properties such by combination high‐temperature annealing (HTA) patterned interfaces are discussed. While beneficial effect HTA demonstrated UVC LEDs, growth relaxed AlGaN buffer layers AlN a challenge. To achieve low dislocation density, applicability investigated.
AlN layers annealed at high temperatures offer low threading dislocation densities of mid 108 cm−2 and are therefore increasingly used as base in ultraviolet (UV) light emitting diode (LED) heterostructure growth. These LEDs, just like those grown on conventional metalorganic vapor phase epitaxy (MOVPE) templates, often suffer from long-wavelength parasitic luminescence. In this work, luminescence properties far-UVC LED heterostructures MOVPE-AlN/sapphire templates high-temperature...
We have devolved 1064 nm high-power monolithic distributed feedback lasers which operate simultaneously on two longitudinal modes. These modes correspond to the fundamental and first-order lateral mode arise from a 7.5 mum width ridge waveguide supporting both of them. They are further stabilized by grating built into an InGaP/GaAs/InGaP multilayer structure. The threshold current laser is 66 mA, slope efficiency 0.5 W/A, output power ~500 mW reached. Detailed investigations intensity...
We report on a nanopixel contact design for nitride-based ultraviolet light-emitting diodes to enhance light extraction. The structure consists of arrays Pd ohmic pixels and an overlying Al reflector layer. Based this twofold increase in the output, compared large area square contacts is demonstrated. Theoretical calculations experiments reveal that spacing 1 μm or less required enable current overlap region between nanopixels due spreading p-GaN layer ensure injection into entire active...