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Szabo Z.,MTA EK Institute of Technical Physics and Materials Science | Baji Z.,MTA EK Institute of Technical Physics and Materials Science | Basa P.,Semilab Semiconductor Physics Laboratory Co. | Czigany Z.,MTA EK Institute of Technical Physics and Materials Science | And 3 more authors.
Applied Surface Science | Year: 2016

Highly conductive and uniform Ga doped ZnO (GZO) films were prepared by atomic layer deposition (ALD) as transparent conductive layers for InGaN/GaN LEDs. The optimal Ga doping concentration was found to be 3 at%. Even for 4" wafers, the TCO layer shows excellent homogeneity of film resistivity (0.8 %) according to Eddy current and spectroscopic ellipsometry mapping. This makes ALD a favourable technique over concurrent methods like MBE and PLD where the up-scaling is problematic. In agreement with previous studies, it was found that by an annealing treatment the quality of the GZO/p-GaN interface can be improved, although it causes the degradation of TCO conductivity. Therefore, a two-step ALD deposition technique was proposed and demonstrated: a "buffer layer" deposited and annealed first was followed by a second deposition step to maintain the high conductivity of the top layer. © 2016 Published by Elsevier B.V. Source

Csordas A.,HAS ELTE Statistical and Biological Physics Research Group | Csordas A.,Eotvos Lorand University | Almasy O.,Eotvos Lorand University | Almasy O.,Semilab Semiconductor Physics Laboratory Co. | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Two species superfluid Fermi gas is investigated on the BCS side up to the Feshbach resonance. Using the Greens's function technique gradient corrections are calculated to the generalized Thomas-Fermi theory including Cooper pairing. Their relative magnitude is found to be measured by the small parameter (d/RTF)4, where d is the oscillator length of the trap potential and RTF is the radial extension of the density n in the Thomas-Fermi approximation. In particular, at the Feshbach resonance the universal corrections to the local density approximation are calculated and a universal prefactor κW=7/27 is derived for the von Weizsäcker-type correction κW(2/2m)(2n1 2/n1 2). © 2010 The American Physical Society. Source

Talagrand C.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP | Boddaert X.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP | Selmeczi D.G.,Semilab Semiconductor Physics Laboratory Co. | Defranoux C.,Semilab Semiconductor Physics Laboratory Co. | Collot P.,Arts et Metiers ParisTech
Thin Solid Films | Year: 2015

This paper reports on an InGaZnO optical study by spectrometric ellipsometry. First of all, the fitting results of different models and different structures are analysed to choose the most appropriate model. The Tauc-Lorentz model is suitable for thickness measurements but a more complex model allows the refractive index and extinction coefficient to be extracted more accurately. Secondly, different InGaZnO process depositions are carried out in order to investigate stability, influence of deposition time and uniformity. Films present satisfactory optical stability over time. InGaZnO optical property evolution as a function of deposition time is related to an increase in temperature. To understand the behaviour of uniformity, mapping measurements are correlated to thin film resistivity. Results show that temperature and resputtering are the two phenomena that affect IGZO uniformity. © 2015 Elsevier B.V. Source

Horvath Zs.J.,Obuda University | Horvath Zs.J.,Hungarian Academy of Sciences | Basa P.,Hungarian Academy of Sciences | Basa P.,Semilab Semiconductor Physics Laboratory Co. | And 6 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

Charge injection and retention behaviors of metal-nitride-oxide-silicon (MNOS) memory structures with Si or Ge nanocrystals embedded at a depth of 3 nm in the nitride layer were studied. The effect of Si nanocrystals on these properties was opposite in comparison with that of Ge nanocrystals. To understand the origin of these opposite effects, the influence of the oxide thickness and of the depth, size and location of semiconductor nanocrystals has been studied on the charging behavior of MNOS non-volatile memory structures by the calculation of electron and hole tunneling probabilities, and by the simulation of memory window, memory hysteresis and retention behavior. For MNOS structures it is obtained that the presence of nanocrystals enhances the charge injection resulting in better performance, but only for structures with thin tunnel oxide layer (below 3 nm), and if the nanocrystals are located close to the oxide/nitride interface. In the case of very high tunneling probability, i.e., of high tunneling currents the system approaches equilibrium and the memory behavior collapses. There is a narrow range of oxide thickness or depth of nanocrystals, where the charging properties change very fast. Retention exhibits a very sharp dependence on the oxide thickness and on depth of nanocrystals as well. Most part of the experimental results can be explained on the basis of the results of simulations. © 2013 Elsevier B.V. All rights reserved. Source

Horvath Z.J.,Hungarian Academy of Sciences | Horvath Z.J.,Obuda University | Molnar K.Z.,Obuda University | Molnar G.,Hungarian Academy of Sciences | And 7 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2012

Charging behaviour of MNOS structures containing Ge nanocrytals embedded at the SiO 2/Si 3N 4 interface are studied by experiments and by calculating tunnelling probabilities of electrons and holes to the conductance or valence band of the nitride layer, respectively, for structures with and without nanocrystals. It is concluded that the optimal charging behaviour of MNOS structures without nanocrystals can be expected for an oxide thickness of 2-3 nm. The presence of semiconductor nanocrystals at the SiO 2/Si 3N 4 interface enhances strongly the tunnelling probability of electrons and holes for structures with thin oxide layers (2-3 nm) at low electric fields, but they do not influence the charging behaviour of structures at high electric fields. The results of calculations are in agreement with the experimental results obtained on MNOS structures with Ge nanocrystals. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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