Indium–silicon co-doping of high-aluminum-content AlGaN for solar blind photodetectors

We report on an indium–silicon co-doping approach for high-Al-content AlGaN layers. Using this approach, very smooth crack-free n-type AlGaN films as thick as 0.5 μm with Al mole fraction up to 40% were grown over sapphire substrates. The maximum electron concentration in the layers, as determined by Hall measurements, was as high as 8×1017 cm−3 and the Hall mobility was up to 40 cm2/Vs. We used this doping technique to demonstrate solar-blind transparent Schottky barrierphotodetectors with the cut-off wavelength of 278 nm

Photoluminescence Inhomogeneity of LGSO : Ce Scintillator Crystal

Spatial distribution of photoluminescence (PL) parameters in Lu2SiO5 : Ce (LSO : Ce) and Lu2xGd2 – 2xSiO5 : Ce (LGSO : Ce) are investigated using confocal microscopy. The PL spectra of both crys-tals are dominated by a single band peaked at 510 nm. A low intensity sub-band peaked at 600 nm is observed in LGSO:Ce. Spatial inhomogeneities down to submicron size are observed in spectral center of mass mapping images of LGSO : Ce while the spatial distributions of spectrally-integrated PL intensity and PL peak position showed no large variations. The inhomogeneities in LGSO : Ce are caused by the spectral variation of the long-wavelength sub-band and are attributed to Ce3+ located in CeO6 polyhedra. The results are explained by Lu / Gd ratio fluctuations in mixed LGSO : Ce crystals. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3526

SPECTROSCOPY OF DEFECTS IN NEUTRON IRRADIATED AMMONO-THERMAL GaN BY COMBINING PHOTOIONIZATION, PHOTOLUMINESCENCE AND POSITRON ANNIHILATION TECHNIQUES

In this work, pulsed photoionization as well as photoluminescence and positron annihilation spectroscopy were combined to detect different species of defects. The GaN crystals, grown by the ammono-thermal method, doped with Mn as well as Mg impurities and irradiated with different fluences of reactor neutrons, were examined to clarify the role of the technological and radiation defects. The evolution of the prevailing photoactive centres was examined by pulsed photoionization spectroscopy. Positron annihilation spectroscopy was applied to reveal vacancy-type defects.Peer reviewe

Laser-induced Heating Of Nanocrystals Embedded In Glass Matrices

Laser-induced heating of nanocrystals embedded in silicate glass matrices has been studied by photoluminescence and Raman scattering. No nonequilibrium optical phonons were found both for cw and 150-ps-long laser pulses in contrast to bulk samples. The measured laser-induced I temperature rise in one sample where the nanocrystal radii are ∼5 nm was found to be in quantitative agreement with a nonlinear theory proposed by Lax for bulk semiconductors. However, in another sample where the nanocrystal radii are only 3 nm, the observed temperature rise at high laser powers was significantly higher than the theoretical prediction. © 1996 American Institute of Physics.801059635966Asada, M., Migamoto, Y., Suematsu, Y., (1986) IEEE J. Quantum Electron., QE-22, p. 1915Hoyer, P., Könenkamp, R., (1995) Appl. Phys. Lett., 66, p. 349Yoffe, A.D., (1993) Adv. Phys., 42, p. 173Shah, J., (1992) Hot Carriers in Semiconductor Nanostructures, Physics and Applications, , Academic, New YorkLax, M., (1977) J. Appl. Phys., 48, p. 3919(1978) Appl. Phys. Lett., 33, p. 786Dobal, P.S., Bist, H.D., Mehta, S.K., Jain, R.K., (1994) Appl. Phys. Lett., 65, p. 2469Duval, E., Boukenter, A., Champagnon, B., (1986) Phys. Rev. Lett., 56, p. 2052Tanaka, A., Onari, S., Arai, T., (1993) Phys. Rev. B, 47, p. 1237Liu, L.C., Risbud, S.H., (1990) J. Appl. Phys., 68, p. 28Rodrigues, P.A.M., Tamulaitis, G., Yu, P.Y., Risbud, S.H., (1995) Solid State Commun., 94, p. 583Borrelli, N.F., Hall, D.W., Holland, H.J., Smith, D.W., (1987) J. Appl. Phys., 61, p. 5399Tu, A., Persans, P.D., (1991) Appl. Phys. Lett., 58, p. 1506Logothetidis, S., Cardona, M., Lautenschlager, P., Garriga, M., (1986) Phys. Rev. B, 34, p. 2458Nomura, S., Kobayashi, T., (1992) Phys. Rev. B, 45, p. 1305Malhotra, J., Hagan, D.J., Potter, B.G., (1991) J. Opt. Soc. Am. B, 8, p. 1531Roussignol, J., Ricard, D., Lukasik, J., Flytzanis, C., (1987) J. Opt. Soc. Am. B, 4, p. 5Kim, D.S., Yu, P.Y., (1991) Phys. Rev. B, 43, p. 4158Mattos, J.C.V., Leite, R.C.C., (1973) Solid State Commun., 12, p. 465Babcock, C.L., (1977) Silicate Glass Technology, , Wiley, New YorkAmmar, M.M., Gharib, S.A., Halawa, M.M., El-Batal, H.A., El-Badry, K., (1983) J. Am. Ceram. Soc., 66, pp. C76Touloukian, Y.S., Thermophysical Properties of Matter (1970) The Thermophysical Properties Research Center Data Series. Vol. 2. Thermal Conductivity-Non-metallic Solids, 2, p. 933. , Plenum, New YorkKapitza, P.L., (1941) J. Phys., 4, p. 181. , Mosco

Indium-Silicon Co-Doping of High-Aluminum-Content AlGaN for Solar Blind Photodetectors

We report on an indium–silicon co-doping approach for high-Al-content AlGaN layers. Using this approach, very smooth crack-free n-type AlGaN films as thick as 0.5 μm with Al mole fraction up to 40% were grown over sapphire substrates. The maximum electron concentration in the layers, as determined by Hall measurements, was as high as 8×1017 cm−3 and the Hall mobility was up to 40 cm2/Vs. We used this doping technique to demonstrate solar-blind transparent Schottky barrierphotodetectors with the cut-off wavelength of 278 nm

Optical bandgap formation in AlInGaN alloys

We report on the spectral dynamics of the reflectivity, site-selectively excited photoluminescence,photoluminescence excitation, and time-resolved luminescence in quaternary AlInGaN epitaxial layers grown on GaN templates. The incorporation of a few percents of In into AlGaN causes significant smoothening of the band-bottom potential profile in AlInGaN layers owing to improved crystal quality. An abrupt optical bandgap indicates that a nearly lattice-matched AlInGaN/GaN heterostructure with large energy band offsets can be grown for high-efficiency light-emitting devices

First study of radiation hardness of lead tungstate crystals at low temperatures

The electromagnetic calorimeter of PANDA at the FAIR facility will rely on an operation of lead tungstate (PWO) scintillation crystals at temperatures near -25 deg.C to provide sufficient resolution for photons in the energy range from 8 GeV down to 10 MeV. Radiation hardness of PWO crystals was studied at the IHEP (Protvino) irradiation facility in the temperature range from room temperature down to -25 deg.C. These studies have indicated a significantly different behaviour in the time evolution of the damaging processes well below room temperature. Different signal loss levels at the same dose rate, but at different temperatures were observed. The effect of a deep suppression of the crystal recovery process at temperatures below 0 deg.C has been seen.Comment: 10 pages 7 figure

Optical Bandgap Formation in AlInGaN Alloys

We report on the spectral dynamics of the reflectivity, site-selectively excited photoluminescence,photoluminescence excitation, and time-resolved luminescence in quaternary AlInGaN epitaxial layers grown on GaN templates. The incorporation of a few percents of In into AlGaN causes significant smoothening of the band-bottom potential profile in AlInGaN layers owing to improved crystal quality. An abrupt optical bandgap indicates that a nearly lattice-matched AlInGaN/GaN heterostructure with large energy band offsets can be grown for high-efficiency light-emitting devices

Transient Absorption Phenomena in Synthetic HPHT and CVD Diamonds for a Fast Timing in Nuclear Instrumentation

In this study, we investigate  transient phenomena in synthetic diamonds  obtained by High Pressure High Temperature and Chemical Vapor Deposition methods. Study was aimed at searching for inorganic crystalline media combining ionizing radiation detecting properties and non-linear absorption of ultra-short laser pulses. The nonlinear pump-and-probe optical absorption technique with of 140 fs laser pulses was used to study the effects

Double-scaled potential profile in a group-III nitride alloy revealed by Monte Carlo simulation of exciton hopping

The temperature dependences of the peak position and width of the photoluminescence band in Al0.1In0.01Ga0.89N layers were explained by Monte Carlo simulation of exciton localization and hopping. The introduction of a doubled-scaled potential profile due to inhomogeneous distribution of indium allowed obtaining a good quantitative fit of the experimental data. Hopping of excitons was assumed to occur through localized states distributed on a 16 meV energy scale within the In-rich clusters with the average energy in these clusters dispersed on a larger (42 meV) scale