I. P. Nikitina

Ioffe Physical Technical Institute, Sankt-Peterburg, St.-Petersburg, Russia

Are you I. P. Nikitina?

Claim your profile

Publications (74)67.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The implementation of control over self-separation of thick GaN flayers grown by Hydride Vapor-Phase Epitaxy (HVPE) on Metal-Organic Chemical Vapor Deposition (MOCVD)-grown templates with patterned nano-column interlayer is reported. Both numerical simulation and experimental data show that separation of thick HVPE layers is provided by non-uniform redistribution of the growth stress. It is shown that the geometrical parameters of the nano-column structure such as fill factor and shape of the columns are most critical for self-separation effect. By adjusting the nano-column pattern, successful self-separation of thick HVPE layers from 2-inch structured MOCVD GaN/sapphire substrate was demonstrated. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 02/2014; 11(3-4). DOI:10.1002/pssc.201300432
  • [Show abstract] [Hide abstract]
    ABSTRACT: Patterned Few Layers Graphene (FLG) films were grown by local solid phase epitaxy from nickel silicide supersaturated with carbon. The process was realised by annealing of thin Ni films deposited on the carbon-terminated surface of 6H-SiC semi-insulating wafer followed by wet processing to remove the resulting nickel silicide. Raman spectroscopy was used to investigate both the formation and subsequent removal of nickel silicide during processing. Characterisation of the resulting FLG films was carried out by Raman spectroscopy and Atomic Force Microscopy (AFM). The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 3 monolayers for initial Ni layers varying from 3 to 20 nm thick. AFM observations revealed process-induced surface roughening in FLG films, however, electrical conductivity measurements by Transmission Line Model (TLM) structures confirmed that roughness does not compromise the film sheet resistance.
    Materials Science Forum 05/2012; 717-720:629-632. DOI:10.4028/www.scientific.net/MSF.717-720.629
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent progress in the field of silicon carbide sensor technology, such as wireless communications and sensors, has demonstrated the need for a resilient energy supply as an alternative to conventional batteries. Previous work has shown that silicon carbide is an effective energy harvester of UV light in high temperature and hostile environments. Until now however, there has been little work undertaken to assess the long-term effects of elevated temperature on such devices. Although it is understood that silicon carbide is unaffected by long-term temperature exposure below 400 °C, there has been little research into the overall device response and how changes in contact metallisation affect the photovoltaic behaviour.
    Materials Science Forum 05/2012; 717-720:997-1000. DOI:10.4028/www.scientific.net/MSF.717-720.997
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrical characteristics of Cr/Au and Ti/Au metal contacts on epitaxial graphene on 4H-SiC showed significant variations in resistance parameters at 300 K. These parameters decreased substantially as the temperature increased to 673 K. The work function, binding energy, and diffusion energy of the deposited metals were used to explain these observed variations. The quantitative analysis of our data demonstrates that non-reactive metals with higher work functions result in lower contact resistance, which can be further decreased by 70% using appropriate annealing. These results provide important information when considering epitaxial graphene for high temperature applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3627167]
    Applied Physics Letters 08/2011; 99(7):073506. DOI:10.1063/1.3627167 · 3.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 3.3 kV rated 4H-SiC diodes with nickel monosilicide Schottky contacts and 2-zone JTE regions were fabricated on commercial epitaxial wafers having a 34 mu m thick blocking layer with donor concentration of 2.2x10(15) cm(-3). The diodes were fabricated with and without additional field stop rings to investigate the impact of practically realizable stopper rings on the diode blocking characteristics. The field stop ring was formed by reactive ion etching of heavily doped epitaxial capping layer. The diodes with field stop rings demonstrated significantly higher yield and reduction of reverse leakage current. The diodes demonstrated blocking voltages in excess of 4.0 kV and very low change of leakage current at ambient temperatures up to 200 degrees C.
    Materials Science Forum 03/2011; 679-680:555-558. DOI:10.4028/www.scientific.net/MSF.679-680.555
  • [Show abstract] [Hide abstract]
    ABSTRACT: Trenched implanted vertical JFETs (TI-VJFETs) with self-aligned gate and source contacts were fabricated on commercial 4H-SiC epitaxial wafers. Gate regions were formed by aluminium implantation through the same silicon oxide mask which was used for etching mesa-structures. Self-aligned nickel silicide source and gate contacts were formed using a silicon oxide spacer formed on mesa-structure sidewalls by anisotropic thermal oxidation of silicon carbide followed by anisotropic reactive ion etching of oxide. Fabricated normally-on 4H-SiC TI-VJFETs demonstrated low gate leakage currents and blocking voltages exceeding 200 V.
    Materials Science Forum 03/2011; 679-680:670-673. DOI:10.4028/www.scientific.net/MSF.679-680.670

  • MRS Online Proceeding Library 01/2011; 640. DOI:10.1557/PROC-640-H2.7
  • [Show abstract] [Hide abstract]
    ABSTRACT: GaN, AIN and AIGaN layers were grown by hydride vapor phase epitaxy. 6H-SiC wafers were used as substrates. Properties of AIN/GaN and AIGaN/GaN structures were investigated. AIGaN growth rate was about 1 μm/min. The thickness of the AIGaN layers ranged from 0.5 to 5 μm. The AIN concentration in AIGaN layers was varied from 9 to 67 mol. %. Samples were characterised by electron beam micro analysis, Auger electron spectroscopy, X-ray diffraction and cathodoluminescence.Electrical measurements performed on AIGaN/GaN/SiC samples indicated that undoped AIGaN layers are conducting at least up to 50 mol. % of AIN.
    MRS Online Proceeding Library 01/2011; 482. DOI:10.1557/PROC-482-245

  • MRS Online Proceeding Library 01/2011; 512. DOI:10.1557/PROC-512-451
  • [Show abstract] [Hide abstract]
    ABSTRACT: Schottky barrier diodes fabricated on Silicon carbide have been demonstrated as gas sensors for deployment in extreme environments. It has been shown that the interfacial layer formed at the Metal – Semiconductor junction, determines both the sensitivity and the reliability of the device. Hence, accurate knowledge of the thickness and interfacial trap density of this layer is required to make predictions of the behaviour of the sensor in the environment under investigation and to predict its variation with time. Diode parameters, such as the ideality factor, barrier height and series resistance have been extracted from experimental measurements on Palladium Schottky Barrier diodes on 4H SiC, over a range of temperatures. The comparison of the parameters extracted from modified Norde function, Cheung's method and Thermonic Emission model has been performed. The variation in the barrier height obtained is quite marked between the different techniques. The reverse I-V characteristics have been used to extract thickness of the interfacial layer, by fitting to the experimental data using the TEBIL model to extract the value of Dit from ä and the ideality factor, assuming the interfacial layer is stoichiometric SiO2 . This allows a comparison between the effective interfacial layer behaviour for the different parameter extraction techniques and demonstrates that knowledge of this interfacial layer is influenced by the technique selected.
    MRS Online Proceeding Library 01/2011; 911. DOI:10.1557/PROC-0911-B10-12
  • [Show abstract] [Hide abstract]
    ABSTRACT: Few Layers Graphene (FLG) films were grown on the carbon-terminated surface of 4H-SiC from nickel silicide supersaturated with carbon. The process was realised by annealing of thin Ni films deposited on silicon carbide followed by wet processing to remove the nickel suicide. To identify and characterize the fabricated FLG films, micro-Raman scattering spectroscopy, AFM and optical microscopy have been used. The films grown on samples with initially deposited nickel thinner than 20 nm show clear graphene footprints in micro-Raman scattering spectra, namely a single component, Lorentzian shape 2D band with FWHM remarkably lower than that of the 2D peak of graphite.
    Materials Science Forum 04/2010; 645-648:589-592. DOI:10.4028/www.scientific.net/MSF.645-648.589
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Free standing AIN wafers were grown on pre-patterned and in situ patterned 4H-SiC substrates by a physical vapor transport method. It is based on the coalescence of AIN microrods, which evolve from the apex of SiC pyramids grown on the SIC substrate during a temperature ramp up for in situ patterned substrate and SiC pyramids formed by reactive ion etching (RIE). This process yields stress-free (according XRD and Raman results) AIN single crystals with a thickness up to 400 mu m and low dislocation density.
    Materials Science Forum 04/2010; 645-648:1187-1190. DOI:10.4028/www.scientific.net/MSF.645-648.1187
  • [Show abstract] [Hide abstract]
    ABSTRACT: 4H-SiC diodes with 0.60 mm(2) nickel silicide Schottky contacts were fabricated on commercial epitaxial layers. At room temperature, the diodes have specific on-resistances (R(ON-SP)) down to 10.5 m Omega xcm(2) and blocking voltages (V(BL)) up to 4.6 kV, which is equal to 93 % of the calculated parallel plane breakdown voltage for used epitaxial structure. The corresponding figure-of-merit, defined as (V(BL))(2)/R(ON-SP), is equal to 2015 MW/cm(2) and is among the highest FOM values reported to date. The diodes demonstrated stable operation at forward current of 1 A and V(BL) value in excess of 3.3 kV at ambient temperatures up to 200 degrees C.
    Materials Science Forum 04/2010; 645-648:897-900. DOI:10.4028/www.scientific.net/MSF.645-648.897
  • [Show abstract] [Hide abstract]
    ABSTRACT: 4H–SiC Schottky diodes with nickel silicide contacts were formed by consecutive deposition of a titanium adhesion layer, 4 nm thick, and nickel, 100 nm thick, followed by annealing at temperatures between 600 and 750 °C. It was found that contacts with barrier heights of 1.45 eV which consist mainly of single nickel monosilicide (NiSi) phase were formed in the 600–660 °C temperature range, while annealing at around 750 °C led to the formation of Ni2Si Schottky contacts with barrier heights of 1.1 eV. Annealing at intermediate temperatures resulted in the nucleation of Ni2Si grains embedded in the NiSi film which were directly observed by micro-Raman mapping. It was shown that the thermodynamically unfavourable NiSi phase appeared in the 600–660 °C temperature range due to control of the Ni–SiC solid-state chemical reaction by nickel diffusion through the titanium diffusion barrier.
    Semiconductor Science and Technology 04/2009; 24(5):055006. DOI:10.1088/0268-1242/24/5/055006 · 2.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Trenched and implanted vertical JFETs (TI-VJFETs) with blocking voltages of 700 V were fabricated on commercial 4H-SiC epitaxial wafers. Vertical p +-n junctions were formed by aluminium implantation in sidewalls of strip-like mesa structures. Normally-on 4H-SiC TI-VJFETs had specific on-state resistance (RON-S) of 8 mΩ.cm2 measured at room temperature. These devices operated reversibly at a current density of 100 A/cm2 whilst placed on a hot stage at temperature of 500 °C and without any protective atmosphere. The change of RON-S with temperature rising from 20 to 500 °C followed a power law (∼ T 2.4) which is close to the temperature dependence of electron mobility in 4H-SiC.
    Materials Science Forum 01/2009; 600-603:1063-1066. DOI:10.4028/www.scientific.net/MSF.600-603.1063
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nickel silicide Schottky contacts were formed on 4H-SiC by consecutive deposition of a titanium adhesion layer, 4 nm thick, and nickel, 100 nm thick, followed by annealing at temperatures from 600 to 750 °C. It was found that contacts with barrier heights of 1.45 eV, consisting mainly of NiSi phase, formed in the 600-660 °C temperature range, while annealing at around 750 °C led to the formation of Ni2Si phase with barrier heights of 1.1 eV. Annealing at intermediate temperatures resulted in the nucleation of Ni2Si grains embedded in the NiSi film which were directly observed by micro-Raman mapping. It was concluded that the thermodynamically unfavourable NiSi phase appeared in the 600-660 °C temperature range due to the fact that the solid state chemical reaction between Ni and SiC at these temperatures is controlled by nickel diffusion through the titanium barrier.
    Materials Science Forum 01/2009; 615-617:577-580. DOI:10.4028/www.scientific.net/MSF.615-617.577
  • [Show abstract] [Hide abstract]
    ABSTRACT: The development of silicon carbide technologies has allowed for the development of sensors and electronics to measure the changes in a variety of hostile environments. A problem has been identified with reliable and efficient ways to power such sensors in these hostile environments. It is likely to be impractical to run power cables to these sensors and battery power has a finite lifetime. Recent research has demonstrated many energy scavenging techniques but to date none have been developed with a view of operation in hostile environments. To investigate the power density achievable from a SiC based energy scavenging device a SiC pin diode was exposed to both broad spectrum light form a tungsten halogen bulb and a 255 nm UV source. IV and CV measurements were used to determine the structural properties and photovoltaic response of the device, dark saturation current, induced photo current and the fill factor. We present the characteristics and maximum power density of these devices at temperatures between 300 K and 600 K. We demonstrate that the maximum power density achievable decreases with temperature. This is mostly due to the reduction in the built in potential from the pn junction, and the reduction of the generated photocurrent.
    Materials Science Forum 01/2009; 615-617:885-888. DOI:10.4028/www.scientific.net/MSF.615-617.885
  • [Show abstract] [Hide abstract]
    ABSTRACT: Buried gate static induction transistors (BGSITs) were fabricated on commercial 4H-SiC wafer with 20 μm thick n-type epilayer having a net donor density of 0.7×1015 cm-3. Buried gate regions were formed by the selective implantation of high energy (up to 2 MeV) aluminium performed at 600 °C. Nitrogen was implanted at temperature of 400 °C to form a heavily doped blanket source region. Post-implantation annealing was carried out at the atmospheric pressure in argon using a graphite capping layer. Fabricated normally-on devices with source contact diameter of 0.2 mm were tested at temperatures up to 500 °C and current densities up to 270 A/cm2. The specific on-resistance of a completely open 4H-SiC BGSIT was 34 mΩ·Cm2 and showed a thermally activated behaviour at temperatures up to 500 °C.
    Materials Science Forum 01/2009; 615-617:735-738. DOI:10.4028/www.scientific.net/MSF.615-617.735
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hole dominated avalanche multiplication and thus breakdown characteristics of ion implanted 4H-SiC p+-n--n+ photodiodes were determined by means of photomultiplication measurements using 325 nm UV light. All the tested diodes exhibited low reverse leakage current and reasonably uniform avalanche breakdown. With avalanche widths of 0.2 µm to 1.5 µm and the capability to measure multiplication factor as low as 1.001, the room temperature impact ionization coefficients were precisely deduced from these 4H-SiC diodes using a local ionization model for electric fields ranging from 1.25 MV/cm to 2.8 MV/cm. The results agree with those reported by Ng et al. and are within the accuracy of both the C-V measurements and electric-field determinations.
    MRS Online Proceeding Library 01/2008; 1069. DOI:10.1557/PROC-1069-D07-12
  • [Show abstract] [Hide abstract]
    ABSTRACT: High voltage 4H-SiC Schottky diodes with single-zone junction termination extension (JTE) have been fabricated and characterised. Commercial 4H-SiC epitaxial wafers with 10, 20 and 45 μm thick n layers (with donor concentrations of 3×1015, 8×1014 and 8×1014 cm-3, respectively) were used. Boron implants annealed under argon flow at 1500°C for 30 minutes, without any additional protection of the SiC surface, were used to form JTE's. After annealing, the total charge in the JTE was tuned by reactive ion etching. Diodes with molybdenum Schottky contacts exhibited maximum reverse voltages of 1.45, 3.3 and 6.7 kV, representing more than 80% of the ideal avalanche breakdown voltages and corresponding to a maximum parallel-plane electric field of 1.8 MV/cm. Diodes with a contact size of 1×1 mm were formed on 10 μm thick layers (production grade) using the same device processing. Characterisation of the diodes across a quarter of a 2-inch wafer gave an average value of 1.21 eV for barrier heights and 1.18 for ideality factors. The diodes exhibited blocking voltages (defined as the maximum voltage at which reverse current does not exceed 0.1 mA) higher than 1 kV with a yield of 21 %.
    Materials Science Forum 09/2007; 556-557:873-876. DOI:10.4028/www.scientific.net/MSF.556-557.873

Publication Stats

836 Citations
67.31 Total Impact Points


  • 1998-2014
    • Ioffe Physical Technical Institute
      • Centre of Nanoheterostructure Physics
      Sankt-Peterburg, St.-Petersburg, Russia
  • 2005-2012
    • Newcastle University
      • School of Electrical and Electronic Engineering
      Newcastle-on-Tyne, England, United Kingdom
  • 1999
    • Russian Academy of Sciences
      Moskva, Moscow, Russia