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...

Nonradiative loss processes are a major concern in nitride-based light emitting devices. Utilizing optical gain measurements on GaInN/GaN/AlGaN laser structures, we have studied the dependence of total recombination rate excess carrier density, up to rather high densities. From detailed quantitative analysis, find room-temperature Auger coefficient 1.8 ± 0.2 × 10−31 cm6/s bandgap range 2.5 − 3.1 eV, considerably lower than previous experimental estimates. Thus, is expected be significant for...

By utilising an asymmetric metallisation scheme to fabricate AlGaN‐based solar‐blind metal–semiconductor–metal photodetector, a zero‐bias external quantum efficiency (EQE) of 24% for illumination at 240 nm wavelength from the substrate side was obtained. Moreover, bias‐dependence dark current and EQE is observed. The saturates about 38% in reverse direction, whereas forward direction presence internal gain mechanism indicated.

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 report on the optical properties of m-plane GaInN/GaN quantum wells (QWs). found that emission energy GaInN QWs grown SiC is significantly lower than non-polar bulk GaN, which we attribute to high density stacking faults. Temperature and power dependent photoluminescence reveals have almost as large internal efficiencies GaN despite much higher defect density. Our results indicate quantum-wire-like features formed by faults intersecting provide a highly efficient light completely...

A comprehensive study on top- and bottom-illuminated Al0.5Ga0.5N/AlN metal-semiconductor-metal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold saturation behavior as a function of applied bias voltage up to 50 V reaching about 50% for 0.1 μm 67% 0.5 thick layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion...

Interferometric gravitational wave detectors require high optical power, single frequency lasers with very good beam quality and amplitude stability as well long-term reliability input light source. For GEO 600 a laser system these properties is realized by stable planar, longitudinally pumped 12 W Nd:YAG rod which injection-locked to monolithic 800 mW non-planar ring oscillator. Frequency control signals from the mode cleaners are fed actuators of oscillator determines system. The power...

Abstract We present Schottky type metal semiconductor (MSM) AlGaN photodetectors (PDs) suited for the ultraviolet C (UV‐C) spectral region grown on conventional planar AlN templates in comparison with epitaxial laterally overgrown (ELO) templates. On solar blind MSM PDs state‐of‐the‐art dark current pA range and a power independent responsivity are obtained. Using ELO sapphire substrates tilted to m direction defect density absorber material is reduced compared that The this exhibit...

The influence of open-core threading dislocations on the bias-dependent external quantum efficiency (EQE) bottom-illuminated Al0.5Ga0.5N/AlN metal-semiconductor-metal (MSM) photodetectors (PDs) is presented. These defects originate at interface and terminate Al0.5Ga0.5N surface as hexagonal prisms. They work electrically active paths bypassing absorber layer therefore alter behavior MSM PDs under bias voltage. This effect included in model carrier collection showing a good agreement with...

The spectral performance of solar‐blind Al x Ga 1– N based metal–semiconductor–metal ultra‐violet photodetectors has been measured for top‐ as well bottom‐illumination at different bias voltages. In the case external quantum efficiency spectra can be tuned between a peak or broad wavelength spectrum by adjusting absorber layer thickness and applied voltage. For thin layers is enhanced factor three, reaching 20% 20 V bias, compared to front‐illumination case. Results two‐dimensional device...

Abstract GaInN/GaN multiple quantum well structures grown on polar and nonpolar surfaces have been compared with respect to the indium incorporation efficiency in wells (QWs). Under same growth conditions X‐ray diffraction measurements reveal similar rates In concentrations for c ‐plane, a m ‐plane contents up 40%. These results are good agreement optical experiments, particular homoepitaxial growth. However, there is strong evidence that properties of heteroepitaxial GaInN QWs dominated by...

Schottky type metal–semiconductor–metal (MSM) Al 0.4 Ga 0.6 N photodetectors (PDs) for the ultraviolet C spectral region on conventional planar AlN templates are compared with epitaxial laterally overgrown (ELO) templates. On solar blind MSM PDs state-of-the-art dark current in pA range and a power independent responsivity obtained. ELO fingers parallel to etched stripes have properties similar those contact oriented perpendicular stripe pattern exhibit photoconductive gain leading external...

Solar blind Al_0.5Ga_0.5N/AlN metal-semiconductor-metal photodetectors (MSM PDs) are characterized by means of photocurrent spectroscopy. In order to enhance the external quantum efficiency (EQE) at low bias voltages several strategies have been adopted including absorber layer thicknesses, electrode layout and metallization scheme. Analysis experimental EQE-bias characteristics under top bottom illumination conditions reveals (1) a correlation between EQE pair density...

We investigated the influence of lifetime and transit time photogenerated carriers on performance visible-blind Al 0.25 Ga 0.75 N metal–semiconductor–metal photodetectors by a combination experimental studies numerical simulations. Good agreement between simulated measured current–voltage ( I – V ) characteristics was achieved for several geometries interdigitated contact structure. Simulations external quantum efficiency (EQE) at low bias voltages showed that long hole in AlGaN absorption...

The degradation of AlGaN-based metal-semiconductor-metal photodetectors under UV illumination has been studied. Oxidation triggered by the presence moisture and mobile carriers at semiconductor surface was found to be mechanism. UVC devices with Al0.5Ga0.5N absorbers show stable performance for more than 1000 h intensities around 10 mW cm−2 low dark current when passivated after metallization SiNx. UVB Al0.25Ga0.75N absorber layers were sensitive here additional protection a thin SiN layer...

The optical gain of single quantum well laser structures on semipolar (112¯2)-GaN in dependence the polarization and resonator orientation has been studied by variable stripe length method. c′-[1123¯] shows maximum TE mode, followed m-[11¯00]-resonator with extraordinary polarization. anisotropic behaviour is explained valence sub-band ordering birefringence wurtzite crystal, resulting a modification transition matrix element for stimulated emission. Measurements are accompanied 6 × k · p...

We developed a visible-red to near-infrared wavelength tunable all-solid-state laser system utilizing an optical parametric generation process in MgO doped PPLN crystal pumped at 532 nm by amplified and frequency doubled picosecond passively Q-switched Nd:YVO4 microchip laser. A broad bandwidth, tuneable over 300 between 710 1015 nm, is accessible. Depending on the green pump light pulse energy, pulses with durations down 69 ps as well energies above 2 µJ were achieved kHz repetition rates.

The bias dependence of the external quantum efficiency (EQE) bottom-illuminated Al0.5Ga0.5N/AlN metal-semiconductor-metal photodetectors shows certain features which are directly related to device geometry, i.e., electrode design and absorber layer thickness. Asymmetric detectors any thickness between 0.5 μm 0.1 show a reduced EQE in reverse saturation. Furthermore, an enhanced appears below threshold either polarity for thick (i.e., μm, 0.3 μm) or forward thin (0.1 AlGaN layers. In order...

Al0.45Ga0.55N metal–semiconductor–metal photodetectors were grown by MOVPE on planar and stripe patterned epitaxial laterally overgrown (ELO) AlN/sapphire templates. By comparing devices different template types, the influence of average dislocation density, distribution dislocations, composition modulations due to inhomogeneous gallium incorporation external quantum efficiency (EQE) evaluated. The reduction density from 6 × 109 cm−2 about 2 ELO increases EQE. For electron transport...

Abstract Solar‐blind Schottky‐type metal‐semiconductor‐metal (MSM) photodetectors (PDs) based on Al x Ga 1–x N absorber layers with varying between 0.4 and 1 are investigated. The impact of the epitaxial lateral overgrowth (ELO) technique stripe patterned AlN/sapphire templates is evaluated by comparing devices ELO as well planar templates. Device characteristics have been found to depend orientation finger‐electrodes respect pattern. responsivity PDs perpendicular stripes higher than that...

We present a monolithic integrated passively Q-switched sub-150 ps microchip laser at 1064 nm with wedged Nd:YVO 4 crystal operating up to repetition rate of 1 MHz. The wedge enables change the cavity length by small amount fine tune spectral mode position over full gain bandwidth and hence optimize output power. This additional degree freedom may be suitable approach increase wafer scale mass production yield or also simplify frequency tuning CW single-frequency lasers.