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    Wyświetlanie 1-9 z 9
    Tytuł:
    High Speed Heterostructure Metal-Semiconductor-Metal Photodetectors
    Autorzy:
    Cola, A.
    Nabet, B.
    Chen, X.
    Quaranta, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041621.pdf
    Data publikacji:
    2005-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    85.60.-q
    73.40.Sx
    06.60.Jn
    Opis:
    In this work we review the properties of a class of metal-semiconductor-metal photodetectors based on heterojunction structures. Particularly, an AlGaAs/GaAs device is detailed in which the absorption region is in the GaAs layer, and a two-dimensional electron gas is formed at the heterointerface due toδ-doping of the widegap material. This heterostructure metal-semiconductor-metal photodetector also contains an AlGaAs distributed Bragg reflector that forms a resonant cavity for detection at 850 nm. The beneficial effect of the two-dimensional electron gas in the GaAs absorption layer in terms of speed and sensitivity is demonstrated by comparing samples with and without doping in the AlGaAs layer. The design and the physical properties of the grown epitaxial structure are presented, together with the static and dynamic characteristics of the device in time domain. In particular, photocurrent spectra exhibit a 30 nm wide peak at 850 nm, and time response measurements give a bandwidth over 30 GHz. A combination of very low dark current and capacitance, fast response, wavelength selectivity, and compatibility with high electron mobility transistors makes this device suitable for a number of application areas, such as Gigabit and 10 Gigabit Ethernet, wavelength division multiplexing, remote sensing, and medical applications.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 1; 14-25
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Defects in Dilute Nitrides
    Autorzy:
    Chen, W. M.
    Buyanova, I. A.
    Tu, C. W.
    Yonezu, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043705.pdf
    Data publikacji:
    2005-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.72.Ji
    71.55.Eq
    76.70.Hb
    Opis:
    We provide a brief review of our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As$\text{}_{a}$ antisites and Ga$\text{}_{i}$ self-interstitials were positively identified. Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 4; 571-579
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    High-Pressure Studies of Semiconductors in the Far-Infrared: Donor States in Quasi-2D
    Autorzy:
    Weinstein, B. A.
    Tischler, J. G.
    Chen, R. J.
    Nickel, H. A.
    McCombe, B. D.
    Dzyubenko, A. B.
    Sivachenko, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2014129.pdf
    Data publikacji:
    2000-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.66.Fd
    73.20.Dx
    73.20.Hb
    Opis:
    We review recent experimental advances by the Buffalo group in performing far-infrared magnetospectroscopy under fine tuning of applied high hydrostatic pressure. Experiments are reported for the effects of pressure on Si donors in modulation doped GaAs/AlGaAs quantum wells. We clearly observe pressure-mediated competition between free (i.e., Landau level) and bound electron states - the latter arising from both neutral (D$\text{}^{0}$) and charged (D$\text{}^{-}$) donor species. With increasing pressure, there is a progression of the observed spectra from being dominated by cyclotron resonance and the D$\text{}^{-}$ singlet (or singlet-like bound magnetoplasmon) transitions, to showing the D$\text{}^{0}$ 1s → 2p$\text{}^{+}$ line. The main reason for this evolution is the decrease in electrons due to the crossover of the Si levels associated with the Γ (well) and X (barrier) conduction minima. Indeed, for pressures above 30 kbar the Γ(well)-X(barrier) crossover quenches all the transitions. However, we find strong evidence that electrons are independently lost to a trap, which becomes active several kbar below this crossing. A possible candidate for this trap is residual Se impurities in the barriers. We present the results of detailed numerical calculation which are found to agree very well with the measured field dependencies of the cyclotron resonance, D$\text{}^{0}$ and D$\text{}^{-}$ transition energies. In the sample with the highest doping, a new transition is observed for fields and pressures above 7.5 T and 5 kbar. Reasons for this apparent anomaly are discussed.
    Źródło:
    Acta Physica Polonica A; 2000, 98, 3; 241-257
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Focused Ion Beam Imaging of Defects in Multicrystalline Si for Photovoltaic Application
    Autorzy:
    Miyamura, Y.
    Sekiguchi, T.
    Chen, J.
    Li, J.
    Watanabe, K.
    Kumagai, K.
    Ogura, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1198415.pdf
    Data publikacji:
    2014-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.05.-a
    61.85.+p
    61.72.Ff
    Opis:
    We demonstrate the imaging of the extended defects in Si materials using a focused ion beam instrument. Since Ga-ion beam has small penetration depth and high channeling character compared with electron beam, the secondary electron signal of focused ion beam is more sensitive to the surface morphology and crystallinity. We have tried to use this secondary electron imaging of focused ion beam for observation of various extended defects in Si materials for photovoltaic and semiconductor devices. As for the texture of multicrystalline Si, some grains are imaged darker than the others. It suggests that the crystal orientation gives different channeling effect on the primary Ga-ion beam, resulting in the different secondary electron yield. The grain boundaries and lineage in multicrystalline Si are shown as bright lines and patterns in the image. Although it may reflect the surface morphologies, these contrasts may be attributed to the channeling contrast due to lattice displacement or distortion. The contrast mechanism of FIB imaging is discussed.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 4; 991-993
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    XANES Study of La$\text{}_{0.75-x}$Gd$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3-δ}$ Solid Solutions
    Autorzy:
    Drozd, V. A.
    Pęka̶a, M.
    Liu, R. S.
    Lee, J.-F.
    Chen, J. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2046755.pdf
    Data publikacji:
    2006-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.47.Lx
    61.10.Ht
    Opis:
    A series of solid solutions La$\text{}_{0. 75-x}$Gd$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3-δ}$ with 0.0≤x≤0.75 was prepared via carbonate precursor precipitation method. Final sintering was performed at 1250ºC in oxygen flow atmosphere. The samples obtained were characterized by scanning electron microscope, X-ray diffraction measurements. Oxygen stoichiometry was analyzed by iodometric titration method. X-ray absorption spectroscopic methods of Mn L-edge and Mn K-edge X-ray absorption near edge structure were used to study oxidation state of manganese in the solid solutions and elucidate features of their local crystal structure. Orthorhombic crystal structure characteristics of the solid solutions were refined by Rietveld method. An increase in oxygen deficiency and average manganese oxidation state were found to accompany Gd concentration increase in La$\text{}_{0.75-x}$Gd$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3-δ}$. These results are consistent with Mn L-edge X-ray absorption near edge structure spectra, where a gradual change of Mn oxidation state with Gd concentration increase was detected. Origins of oxygen deficiency La$\text{}_{0.75- x}$Gd$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3-δ}$ are discussed in terms of structural disorder caused by Gd substitution for La.
    Źródło:
    Acta Physica Polonica A; 2006, 109, 4-5; 583-589
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer
    Autorzy:
    Cieplak, M. Z.
    Adamus, Z.
    Konczykowski, M.
    Chen, X. M.
    Byczuk, A.
    Abal'oshev, A.
    Sang, Hai.
    Chien, C. L.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041450.pdf
    Data publikacji:
    2004-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.25.Ha
    74.25.Qt
    74.78.Db
    74.78.Fk
    Opis:
    The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model.
    Źródło:
    Acta Physica Polonica A; 2004, 106, 5; 693-698
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Transport and Microwave Noise in MBE- and MOCVD-Grown AlGaN/AlN/GaN
    Autorzy:
    Matulionis, A.
    Liberis, J.
    Eastman, L. F.
    Schaff, W. J.
    Shealy, J. R.
    Chen, X.
    Sun, Y. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041771.pdf
    Data publikacji:
    2005-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    63.20.Kr
    72.20.Ht
    73.40.Kp
    Opis:
    Microwave noise temperature, current, and dissipated power were investigated at room temperature in undoped AlGaN/AlN/GaN channels grown by molecular beam epitaxy and metal-organic compound vapour decomposition techniques. Samples with essentially the same electron density (1×10$\text{}^{13}$ cm$\text{}^{-2}$) and low-field mobility (1150 cm$\text{}^{2}$/(V s)) demonstrated considerably different behaviour at high electric fields. The effective hot-phonon lifetime, 300 fs and 1000 fs, respectively, was estimated for molecular beam epitaxy and metal-organic compound vapour decomposition samples. The expected anti-correlation of hot-phonon lifetime and hot-electron drift velocity was confirmed experimentally.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 2; 361-364
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Luminescence of Highly Excited Nonpolar a-Plane GaN and AlGaN/GaN Multiple Quantum Wells
    Autorzy:
    Juršėnas, S.
    Kuokštis, E.
    Miasojedovas, S.
    Kurilčik, G.
    Žukauskas, A.
    Chen, C. Q.
    Yang, J. W.
    Adivarahan, V.
    Asif Khan, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2038100.pdf
    Data publikacji:
    2004-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.55.Cr
    73.21.Fg
    72.20.Jv
    78.47.+p
    Opis:
    Carrier recombination dynamics in polar and nonpolar GaN epilayers and GaN/AlGaN multiple quantum wells grown over sapphire substrates with various crystallographic orientation were studied under high photoexcitation by 20 ps laser pulses. The transient of luminescence featured a significant enhancement in nonradiative recombination of free carriers for nonpolar a-plane GaN epilayers compared to conventional c-plane samples. The epitaxial lateral overgrowth technique was demonstrated to significantly improve the quality of nonpolar a-plane films. This was proved by more than 40-fold increase in luminescence decay time (430 ps compared to ≤10 ps in the ordinary a-plane epilayer). Under high-excitation regime, a complete screening of built-in electric field by free carriers in multiple quantum wells grown on c-plane and r-plane sapphire substrates was achieved. Under such high excitation, luminescence efficiency and carrier lifetime of multiple quantum wells was shown to be determined by the substrate quality.
    Źródło:
    Acta Physica Polonica A; 2004, 105, 6; 567-573
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Luminescence of Highly Photoexcited GaN Epilayers and Heterostructures Grown on Different Sapphire Crystal Planes
    Autorzy:
    Juršėnas, S.
    Miasojedovas, S.
    Kurilčik, G.
    Liuolia, V.
    Žukauskas, A.
    Chen, C. Q.
    Yang, J. W.
    Kuokštis, E.
    Adivarahan, V.
    Asif Khan, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041736.pdf
    Data publikacji:
    2005-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.55.Cr
    73.21.Fg
    72.20.Jv
    78.47.+p
    Opis:
    GaN epilayers and AlGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition on different crystal planes (c, a, and r) of the sapphire substrate were studied by excitation intensity dependent and time-resolved photoluminescence. In polar multiple quantum wells grown on a- and c-planes, a blueshift of the luminescence band with increasing the excitation energy was observed, indicating that screening of built-in field by free carriers takes place, whereas in nonpolar r-plane grown multiple quantum wells, the luminescence band maintained an almost constant peak position. Full screening of built-in field was achieved at the excitation densities higher than 0.3 mJ/cm$\text{}^{2}$. Under conditions of screened built-in electric field the structures were characterized by carrier lifetime. It was shown that nonpolar multiple quantum wells suffer from high density of nonradiative traps that can be due to substrate related threading dislocations.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 2; 235-239
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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