Master’s Theses

  • Title: Optimization of the preparation of 2D transition metal sulfides for supercapacitors
    Supervisor: Mgr. M. Sojková, PhD. ( Dpt. Microelectronics and Sensors IEE SAS)
    Ing. Peter Ondrejka, PhD. (ÚJFI FEI STU)
    Stud. Programma: Electronics and Photonics
  • Title: Development of GaN-based power transistors for electric vehicles
    Supervisor: Ing. Michal Blaho, PhD. (Dpt. III-V Semiconductors IEE SAS)
    doc. Ing. Aleš Chvála, PhD. (FEI STU)
    Stud. Programma: Electronics and Photonics
    There is an expected significant increase of number of electric vehicles (EV) from today’s few million up to 125 million in 2035. Such tremendous increase in EV production requires development of new power electronic components enabling production of cost-effective, light-weight, and more efficient systems for electric propulsion and charging. Currently, commercially available power devices work up to 600 V region. Yet, this rating is far below theoretical capability of the GaN material capabilities. Enhancement to higher voltage ratings up to 900 V is possible by increasing the quality of GaN epitaxial layers. This can be achieved by replacing the substrate material for GaN growth from typically-used silicon, which dominates due to its low cost, with silicon carbide (SiC), which allows to use the full potential of gallium nitride.
    The main goal of this thesis will be the fabrication and characterisation of transistors based on GaN thin films grown by metalorganic chemical vapour deposition (MOCVD) at the IEE SAS. Main focus will be on the fabrication of GaN-based transistors using modern technological approaches (e.g. photolithography, plasma etching, atomic layer deposition,..) and advanced electrical characterisation of prepared structures. Acquired knowledge will be used for further optimisation of epitaxial growth of GaN layers within the framework of our currently implemented national and international research projects.
  • Title: Fabrication of microelectronic devices based on ultrawide bandgap semiconducting Ga2O3 and study of their thermal performance
    Supervisor: Ing. Filip Gucmann, PhD. ( Dpt. III-V Semiconductors IEE SAS)
    Ing. Juraj Priesol, PhD. (Ústav elektroniky a fotoniky, FEI STU)
    Stud. Programma: Electronics and Photonics
    Current semiconductor material research for next-generation electronic devices shows an on-going long-time interest in materials with bandgap energies (Eg) exceeding that of Si. While GaN and SiC have long time been materials of choice, other candidates such as high-Al content AlGaN, diamond, and gallium oxide (Ga2O3) are becoming increasingly more attractive for high voltage/high power applications. Owing to a relatively simple synthesis of bulk crystals and epitaxial layers, ultrawide bandgap (Eg ~5 eV), and high theoretical breakdown field (Ecr ~8 MV/cm), Ga2O3 is a very promising material for high reverse blocking voltage (>8 kV) electronic devices and eventually for high-power switching.
    Such devices can enable and accelerate development of electric means of transportation or high-voltage DC-DC voltage levels conversion systems for future low-loss DC power distribution networks and thus significantly contribute to lowered conversion losses, large-scale deployment of electric cars and heavy-goods vehicles and future low-carbon economy.
    The scope of this work covers fabrication of microelectronic devices (e.g. diodes, transistors) based on semiconducting Ga2O3, and study of their thermal performance, mainly their thermal resistance (Rth). Rth will be measured and evaluated by a suitable device thermometry technique, e.g. by gate resistance thermometry which relies on temperature-dependent change in the resistance of the metallic electrode.
    For this study, we will use modern technological equipment and methods, available at the Faculty of Electrical Engineering and Information Technology STU and Institute of Electrical Engineering SAS.
  • Title: Temperature analysis of transport properties of thin InN layer grown on Mg-doped InAlN buffer layers using Van der Pauw and Hall measurement techniques
    Supervisor: Ing. Roman Stoklas, PhD. (Dpt. III-V Semiconductors IEE SAS)
    Ing. Aleš Chvála, PhD. (UEF FEI STU)
    Stud. Programma: Electronics and Photonics
    The speed performance of transistors is mainly dependent on the electron drift velocity along the channel and also on the gate length. Consequently, drift velocity is the most important material parameter, defining the switching speed of electronic devices. According to theoretical calculations, InN provides the highest steady-state electron drift velocity among all semiconductors, with a value of ∼5–6 × 107 cm s-1. In collaboration with the University of Crete (FORTH) we demonstrate state-of-the-art InN layer with an electron drift velocity of about 108 cm s-1 at an electric field of 48 kV/cm. This is the highest steady-state electron velocity ever measured in any solid-state device. However, this value were analyzed on relatively thick InN layer (700nm). For transistor applications the thin InN channel layer are highly recommended. The InAlN-based structures doped by Mg are used as buffer layer for HFET transistors with InN channel. The main reason is to reduce a high electron concentration accumulated on the surface of InAlN and to reduce the leakage current of the transistor.
    The main aims of the diploma thesis will be an understanding of the basic principles of the Van der Pauw and Hall measurement techniques. In addition, temperature dependent tests of devices can help us to investigate the scattering mechanisms, and drift velocity behaviour, which is highly desirable for the design of the transistors with the thin InN channel layer for THz region.
  • Title: Fabrication and characterization of Ga2O3 transistors for applications in kV range
    Supervisor: Ing. M. Ťapajna, PhD. ( Dpt. III-V Semiconductors IEE SAS)
    Ing. Peter Ondrejka, PhD. (ÚE FEI STU)
    Stud. Programma: Electronics and Photonics
    Current electronic power device market is mostly covered by Si (<1kV voltage range) and SiC and GaN (up to several kV) devices. At present, however, there are practically no semiconductor power devices available for and above the 10 kV range. Gallium oxide (Ga2O3) is a promising ultra-wide bandgap (Eg=4.8–5.3 eV) semiconductor material, which offers technological potential for design of new electronic devices capable of handling this voltage range. Such devices can enable development of systems for transportation utilising electric drive (cars, trains, ships, aircrafts) or transformation for high-voltage DC power distribution networks. The aim of the work will be the preparation and electrical characterization of transistors based on Ga2O3 layers prepared at the Institute of Electrical Engineering of the Slovak Academy of Sciences, v.v.i. The work will focus on the fabrication of a simple MOSFET-type transistor and detailed electrical characterization of the prepared devices. The electrical breakdown mechanism of the prepared devices will also be analyzed.
  • Title: The calculation of energy barriers between magnetic states
    Supervisor: Ing. Jaroslav Tóbik, PhD. ( Dpt. Physics and Technology at Nanoscale IEE SAS)
    Stud. Programma: Physics
    Annotation: A ferromagnetic system can be in different states under the same external conditions. This is the origin of hysteresis or memory effect in magnetic systems. The stability of magnetic states is caused by the presence of energy barriers between individual states. For practical applications, it is important to be able to determine or manipulate energy barriers. The goal of this project is to calculate the energy barriers using the metadynamics algorithm and to find out if it is possible to prepare an array of self-organized chiral magnetic states.
  • Title: Diode gas sensors suitable for in-sensor computing
    Supervisor: Ing. Boris Hudec, PhD. ( Dpt. Physics and Technology at Nanoscale IEE SAS)
    prof. Ing. Peter Ballo (FEI STU)
    Stud. Programma: Physical engineering