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.

For AlGaN-based multi-quantum-well light emitters grown on c-plane substrates there is a tendency for the polarization of emitted to switch from transverse electric (TE) magnetic (TM) as wavelength decreases. This transition depends various factors that include strain in quantum well. Experimental results are presented illustrate phenomenon nitride emitting diodes (LEDs) sapphire and bulk AlN. Model calculations which quantify dependence TE/TM well Al composition barriers surrounding

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...

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...

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,...

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...

AlGaN-based far-UVC light emitting diodes (LEDs) with an emission wavelength of 233 nm were fabricated in the form micro-LED arrays emitter diameters ranging from 1.5 to 50 μm. The mesa was plasma etched a sidewall angle 45°–50°, and insulator layers made SiNx or SiO2 deposited. While external quantum efficiency (EQE) LEDs showed only small dependency on diameter, using increase peak EQE by factor four as compared large area devices. This enhancement is attributed strong extraction due total...

Ultraviolet light-emitting diodes (LEDs) suffer from a low wall-plug efficiency, which is to large extent limited by the poor light extraction efficiency (LEE). A thin-film flip-chip (TFFC) design with roughened N-polar AlGaN surface can substantially improve this. We here demonstrate an enabling technology realize TFFC LEDs emitting in UVB range (280-320 nm), includes standard LED processing combination electrochemical etching remove substrate. The integration of achieved epitaxial...

UV light emitters in the UV-B spectral range between 280 nm and 320 are of great interest for applications such as phototherapy, gas sensing, plant growth lighting, curing. In this paper we present high power LEDs grown by MOVPE on sapphire substrates. By optimizing heterostructure design, parameters processing technologies, significant progress was achieved with respect to internal efficiency, injection efficiency extraction. LED chips emitting at 310 maximum output powers up 18 mW have...

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...

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...

Abstract We introduce a novel material for integrated photonics and investigate aluminum gallium nitride (AlGaN) on (AlN) templates as platform developing reconfigurable on-chip nonlinear optical devices. AlGaN combines compatibility with standard photonic fabrication technologies high electro-optic modulation capabilities low loss over broad spectral range, from UVC to long-wave infrared, making it viable complex applications. In this work, we design grow AlGaN/AlN heterostructures...

The degradation of the electrical and optical properties (InAlGa)N-based multiple quantum well light emitting diodes (LEDs) near 308 nm under different stress conditions has been studied. LEDs with emission areas were operated at room temperature constant current densities 75 A/cm2, 150 225 A/cm2. In addition, heat sink was varied between 15 °C 80 °C. Two main modes for reduction power found, which dominate times operation: (1) Within first 100 h, a fast drop is observed scaling...

The effect of different Al(Ga)N electron blocking heterostructures (EBH) on the emission spectra and light output power 290 nm emitting diodes (LEDs) has been investigated. carrier injection internal quantum efficiency LEDs is simulated compared to electroluminescence measurements. highest found for with an Mg-doped AlN/Al0.7Ga0.3N EBH AlN layer thickness >3 nm. these was 8.5-times higher without EBH. This attributed improved confinement which prevents leakage into p-doped region LED...

The electroluminescence from near ultraviolet (UV) light emitting diodes containing InGaN multiple quantum wells (MQWs) with GaN, AlGaN, and InAlGaN barriers was investigated. Based on band-structure calculations the observed wavelength shift in peak emission increasing injection current is attributed to screening of polarization fields band gap renormalization. MQWs almost zero net have been realized. No blueshift spectra these devices over entire range.

Ultraviolet light is essential for disinfection, fluorescence excitation, curing, and medical treatment. An ultraviolet source with the small footprint excellent optical characteristics of vertical-cavity surface-emitting lasers (VCSELs) may enable new applications in all these areas. Until now, there have only been a few demonstrations ultraviolet-emitting VCSELs, mainly optically pumped, low Al-content AlGaN cavities emission near bandgap GaN (360 nm). Here, we demonstrate an pumped VCSEL...

The temperature and strain dependence of the polarization in-plane electroluminescence (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in ultraviolet spectral range has been investigated. For with emission wavelength shorter than 300 nm transversal-electric polarized intensity increases relative to transversal-magnetic increasing temperature, whereas it decreases for longer wavelength. This effect can be attributed occupation deeper valence bands temperature. In...

The effects of the heterostructure design on injection efficiency and external quantum ultraviolet (UV)-B light emitting diodes (LEDs) have been investigated. It was found that functionality AlxGa1−xN:Mg electron blocking layer is strongly influenced by its aluminum mole fraction x magnesium doping profile. By comparing LED electroluminescence, well photoluminescence, simulations heterostructure, we were able to differentiate contributions internal UV LEDs. For optimized using an...

The degradation behavior of ultraviolet-B light emitting diodes (UV-B LEDs) near 310 nm has been investigated and a method to localize the effects is presented. Measurements electro-optical characteristics UV-B LEDs, during 200 h constant-current study, showed an initial fast decrease in optical power accompanied by drive voltage increase capacitance. Furthermore, using specially designed contact geometry, it was possible separate electrical properties p-layers p-contacts from active region...

We demonstrate the first electrically injected AlGaN-based ultraviolet-B resonant-cavity light-emitting diode (RCLED). The devices feature dielectric SiO2/HfO2 distributed Bragg reflectors enabled by tunnel junctions (TJs) for lateral current spreading. A highly doped n++-AlGaN/n++-GaN/p++-AlGaN TJ and a top n-AlGaN spreading layer are used as transparent contacts, resulting in good up to an active region mesa diameter of 120 μm. To access N-face side device, substrate is removed...

Abstract The effects of the aluminum content x and magnesium doping concentration in Al Ga N:Mg electron blocking layer on emission characteristics ultraviolet light‐emitting diodes has been investigated. carrier injection is simulated compared with electroluminescence measurements. light output power depends strongly mole fraction as well supply vapor phase during growth layer. highest found for an around 44% Mg/III‐ratio 3.0% wavelength near 320 nm. This effect can be attributed to...

We report on a chip design which allows the laser lift-off (LLO) of sapphire substrate sustaining epitaxial film flip-chip mounted deep ultraviolet light emitting diodes. A nanosecond pulsed excimer with wavelength 248 nm was used for LLO. mechanically stable found to be key prevent crack formation in layers and material chipping during LLO process. Stabilization achieved by introducing Ti/Au leveling layer that supports fragile film. The electrical optical characterization devices before...