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Cico K.,Slovak Academy of Sciences | Husekova K.,Slovak Academy of Sciences | Apajna M.,Slovak Academy of Sciences | Gregusova D.,Slovak Academy of Sciences | And 7 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2011

The authors report on preparation and electrical characterization of InAlN/AlN/GaN metal-oxide-semiconductor (MOS) high electron mobility transistors (HEMTs) with Al2 O3, ZrO2, and GdScO 3 gate dielectrics. About 10 nm thick high- κ dielectrics were deposited by metal organic chemical vapor deposition after the Ohmic contact processing. Application of the gate dielectrics for 2 μm gate length MOS HEMTs leads to gate leakage current reduction from four to six orders of magnitude compared with Schottky barrier HEMTs. Among others, MOS HEMTs with an Al2 O3 gate dielectric shows the highest transconductance (∼150 mS/mm) and maximum drain current (∼0.77 A/mm) and the lowest sheet resistance of ∼260 ω. MOS HEMTs with GdScO3 shows the highest breakdown electric field of about 7.0 MV/cm. A deep level transient spectroscopy (DLTS) based analysis revealed the maximum interface state density Dit up to 4× 1012, 9× 1012, and 3× 1013 eV-1 cm-2 for Al2 O3, ZrO 2, and GdScO3 /InAlN interface, respectively. © 2011 American Vacuum Society. Source


Mor F.M.,Institute of Condensed Matter Physics ICMP | Sienkiewicz A.,Institute of Condensed Matter Physics ICMP | Forro L.,Institute of Condensed Matter Physics ICMP | Jeney S.,Institute of Condensed Matter Physics ICMP
ACS Photonics | Year: 2014

Near-infrared (NIR) light sensitive lanthanide-doped NaYF4 upconversion particles (UCPs) are gaining increasing attention as local probes in biomedical applications. Here, we implemented a photonic force microscope (PFM) to manipulate and study the optical properties of trapped single UCPs, β-NaYF4:Yb,Er. In particular, we focused on the mechanisms of the optical trapping of nonspherical UCPs of different sizes, in the range 0.5-2 μm, as well as on their upconversion photoluminescence (UCL) properties under excitation with the strongly focused laser beam (λ = 1064 nm) of the PFM, operating at power densities up to 14.7 MW cm-2. A careful analysis of UCL under such conditions points to three emission peaks at 469, 503.6, and 616.1 nm, which were enhanced by the high laser power density. The analysis of Brownian motion was used to quantify the thermal fluctuations of the particle inside the optical trap as well as the particle sizes and optical forces acting in the two dimensions perpendicular to the optical axis. A steep dependence of UCL as a function of the particle diameter was found for UCPs having sizes smaller than the focal spot (∼900 nm) of the NIR laser. (Figure Presented). © 2014 American Chemical Society. Source

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