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  • Ion irradiation-induced polycrystalline InSb foam

    2018-09-28

    InSb films with various thicknesses were deposited by magnetron sputtering on SiO2/Si substrates and subsequently irradiated with 17 MeV Au+7 ions. The structural and electronic changes induced by ion irradiation were investigated by synchrotron and laboratory based techniques. Ion irradiation of InSb transforms compact films (amorphous and polycrystalline) in open cell solid foams. The initial stages of porosity were investigated by transmission electron microscopy analysis and reveal the porous structure initiates as small spherical voids with approximately 3 nm in diameter. The evolution of porosity was investigated by scanning electron microscopy images, which show that film thickness increases up to 16 times with increasing irradiation fluence. Here we show that amorphous InSb films become polycrystalline foams upon irradiation with 17 MeV Au+7 ions at fluences above 1014 cm−2. The films attain a zincblende phase, with crystallites randomly oriented, similarly to the polycrystalline structure attained by thermal annealing of unirradiated films. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • Surface photo-voltage characterization of GaAs/AlGaAs single quantum well laser structures grown by molecular beam epitaxy

    2018-09-20

    We present surface photo-voltage (SPV) measurements on molecular beam epitaxy (MBE) grown single quantum well (SQW) laser structures. Each layer in the hetero-structure has been identified by measurement of the SPV signal after a controlled sequential chemical etching process. These results have been correlated with high resolution x-ray diffraction and photoluminescence (PL) measurements. Quantum confined Stark effect and the carrier screening of electric field have been taken into consideration both theoretically and experimentally to account for the differences observed in SPV and PL results. It is shown that SPV can be used as a very effective tool for evaluation of hetero-structures involving multiple layers. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • Titania–germanium nanocomposite for photo-thermo-electric application

    2018-09-13

    The introduction of germanium (Ge) into titania (TiO2) creates an attractive semiconductor. The new semiconductor is named titania–germanium (TiO2–Ge). Ge dots are dispersed in the distorted TiO2 matrix of TiO2–Ge. The quantum Bohr radius of Ge is 24.3 nm, and hence the properties of the Ge dot can be varied by tailoring its size if it is smaller than its Bohr radius due to the quantum confinement effect (QCE). Therefore, simply by changing the Ge concentration, the morphology of TiO2–Ge can be varied within a wide range. Consequently, the optical, electronic and thermal properties of TiO2–Ge can be tailored. TiO2–Ge becomes a promising material for the next generation of photovoltaics as well as thermoelectric devices. It could also be used for photo-thermo-electric applications. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • Characteristics of liquid phase deposited SiO2 on (NH4)2S-treated GaAs with an ultrathin Si interface passivation layer

    2018-09-05

    The characteristics of liquid-phase-deposited SiO2 film on GaAs were investigated. A mixture of H2SiF6 and H3BO3 aqueous precursors was used as the growth solution. SiO2 on GaAs with (NH4)2S treatment shows good electrical characteristics owing to the reduction of native oxides and sulfur passivation. The electrical characteristics are further improved with an ultrathin Si interface passivation layer (Si IPL) from the reduction of Fermi-level pinning and interface state density. Moreover, during the SiO2 deposition, HF in the growth solution can simultaneously and effectively remove native oxides on Si IPL and provide fluorine passivation on it. The Al/SiO2/Si IPL/(NH4)2S-treated GaAs MOS capacitor shows superior electrical properties. The leakage current densities can reach 7.4 × 10−9 and 6.83 × 10−8 A/cm2 at ±2 V. The interface state density can reach a 2.11 × 1011 cm−2 eV−1 with low frequency-dispersion of 8%. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • Growth and characterization of epitaxial ultra-thin NbN films on 3C-SiC/Si substrate for terahertz applications

    2018-08-29

    We report on electrical properties and microstructure of epitaxial thin NbN films grown on 3C-SiC/Si substrates by means of reactive magnetron sputtering. A complete epitaxial growth at the NbN/3C-SiC interface has been confirmed by means of high resolution transmission electron microscopy (HRTEM) along with x-ray diffractometry (XRD). Resistivity measurements of the films have shown that the superconducting transition onset temperature (TC) for the best specimen is 11.8 K. Using these epitaxial NbN films, we have fabricated submicron-size hot-electron bolometer (HEB) devices on 3C-SiC/Si substrate and performed their complete DC characterization. The observed critical temperature TC = 11.3 K and critical current density of about 2.5 MA  cm − 2 at 4.2 K of the submicron-size bridges were uniform across the sample. This suggests that the deposited NbN films possess the necessary homogeneity to sustain reliable hot-electron bolometer device fabrication for THz mixer applications. Source:IOPscience For more information, please visit our website: semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • An RF MEMS switch with a differential gap between electrodes for high isolation and low voltage operation

    2018-08-22

    A double-actuation RF microelectromechanical system (MEMS) switch with high isolation and low voltage operation for RF and microwave applications is presented. The operation voltage of the suggested double-actuation vertical RF MEMS switch structure was reduced without decreasing the actuation gap. Theoretically, the operation voltage of the suggested structure is about 29% lower than that of a single-actuation vertical RF MEMS switch with the same fabrication method, electrode area and equal contact gap. The proposed RF MEMS switch was fabricated by surface micromachining with seven photo-masks on a quartz wafer. To achieve planarization and the stair-like structure, a polyimide sacrificial layer was spin-coated, cured and etched in two steps and patterned by a dry etching step which defines the double-actuation mechanism. The measured results of the fabricated RF MEMS switch demonstrate that the insertion loss was lower than 0.11 dB for the 20 V ON state, the isolation was higher than 39.1 dB for the OFF state and the return loss was better than 32.1 dB for the 20 V ON state from dc to 6 GHz. The minimum pull-in voltage of the fabricated RF MEMS switch was 10 V. Source:IOPscience For more information, please visit our website:www.semiconductorwafers.net, send us email atangel.ye@powerwaywafer.comorpowerwaymaterial@gmail.com

  • Type-I mid-infrared InAs/InGaAs quantum well lasers on InP-based metamorphic InAlAs buffers

    2018-08-14

    InAs/InGaAs quantum well laser structures have been grown on InP-based metamorphic In0.8Al0.2As buffers by gas source molecular beam epitaxy. The effects of barrier and waveguide layers on the material qualities and device performances were characterized. X-ray diffraction and photoluminescence measurements prove the benefits of the strain compensation in the active quantum well region on the material quality. The device characteristics of the lasers with different waveguide layers reveal that the separate confinement heterostructure plays a crucial role on the device performances of these metamorphic lasers. Type-I emissions in the 2–3 µm range have been achieved in these InP-based metamorphic antimony-free structures. By combining the strain-compensated quantum wells and separate confinement heterostructures, the laser performances have been improved and laser emission up to 2.7 µm has been achieved. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

  • Characterization of GaSb photodiode for gamma-ray detection

    2018-08-10

    We extract the carrier mobility-lifetime products for epitaxially grown GaSb and demonstrate the spectral response to gamma rays of a GaSb p–i–n photodiode with a 2-µm-thick absorption region. Under exposure from 55Fe and 241Am radioactive sources at 140 K, the photodiode exhibits full width at half maximum energy resolutions of 1.238 ± 0.028 and 1.789 ± 0.057 keV at 5.89 and 59.5 keV, respectively. We observe good linearity of the GaSb photodiode across a range of photon energies. The electronic noise and charge trapping noise are measured and shown to be the main components limiting the measured energy resolutions. Source:IOPscience For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

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