Semiconductor Device Materials

This unit is working on the development of novel semiconductor materials for high-frequency and power electronics. The research also focuses on developing spectroscopic techniques for studying electronic and transport properties of materials from bulk to nanoscale.

III-Nitrides for applications in the next generation of wireless communication, sensing, and power infrastructures. The research focuses on optimization of epitaxial design and properties of GaN and AlGaN device structures on SiC, GaN and AlN substrates by hot-wall MOVPE. The activity covers growth of the device structures with the main aim to minimize defect densities (dislocations and background impurities), and the design of the epi-stack targeting different functionalities, e.g. power amplification, noise, and flicker-noise, switch losses, device design, etc.

Terahertz ellipsometry and optical Hall effect. We have developed unique THz ellipsometry and magneto-ellipsometry (optical Hall effect) instrumentation at the Terahertz Materials Analysis Center. These novel techniques makes it possible to explore electronic, transport and magnetic properties and phenomena in e.g, semiconductors, nanomaterials, organic materials, which cannot be assessed by other means. Current research efforts include application of THz to FIR ellipsometry to study 2DEG in transistor and quantum structures, 2D materials, conductive polymers, proteins and biomaterials.

Ultra-wide bandgap semiconductors. Main focus is put on β-Ga2O3 for applications in high-power electronic devices with substantial efficiency gain in e.g., generation and transmission of electric power, electrification of vehicles and motor drivers. Current research efforts include development of MOVPE of β-Ga2O3 and profound understanding of phonon, free charge carrier and electronic properties in relation to microstructure of thin films and device heterstructures.

2D materials. Current research activities include using THz ellipsometry to study, understand and optimize the transport, electronic and structural properties of e.g., epitaxial graphene grown on SiC, MAXens, and BN.

Publications

2025

Hengfang Zhang, Jr-Tai Chen, Alexis Papamichail, Ingemar Persson, Dat Tran, Plamen Paskov, Vanya Darakchieva (2025) Effect of substrate misorientation angle on the structural properties of N-polar GaN grown by hot-wall MOCVD on 4H-SiC(000(1)over-bar) Journal of Crystal Growth, Vol. 651, Article 127971 (Article in journal) Continue to DOI

2024

Adamantia Logotheti, Navya Sri Garigapati, Byeongchan So, Jovana Colvin, Vanya Darakchieva, Erik Lind (2024) Low Resistivity n-type GaN Ohmic Contacts on GaN Substrates Physica Status Solidi (a) applications and materials science (Article in journal) Continue to DOI
Bjorn Hult, Johan Bergsten, Ragnar Ferrand-Drake Del Castillo, Vanya Darakchieva, Anna Malmros, Hans Hjelmgren, Mattias Thorsell, Niklas Rorsman (2024) Characterization of Drain-Induced Barrier Lowering in GaN HEMTs Using a Drain Current Injection Technique IEEE Transactions on Electron Devices (Article in journal) Continue to DOI
Hui Zeng, Weimin Wang, Ivan Gueorguiev Ivanov, Vanya Darakchieva, Jianwu Sun (2024) Determination of the conduction and valence band offsets at the Co3O4/3C-SiC p-n heterojunction Applied Physics Letters, Vol. 125, Article 162102 (Article in journal) Continue to DOI
Alyssa Mock, Steffen Richter, Alexis Papamichail, Vallery Stanishev, Misagh Ghezellou, Jawad Ul-Hassan, Andreas Popp, Saud Bin Anooz, Daniela Gogova-Petrova, Praneeth Ranga, Sriram Krishnamoorthy, Rafal Korlacki, Mathias Schubert, Vanya Darakchieva (2024) Effective uniaxial dielectric function tensor and optical phonons in (¯2⁢01)-oriented ��-Ga2⁢O3 films with equally distributed sixfold-rotation domains Physical Review Applied, Vol. 22, Article 044003 (Article in journal) Continue to DOI
Alexis Papamichail, Axel Persson, S. Richter, Vallery Stanishev, Nerijus Armakavicius, Philipp Kuhne, S. Guo, Per O A Persson, Plamen Paskov, N. Rorsman, Vanya Darakchieva (2024) Impact of Al profile in high-Al content AlGaN/GaN HEMTs on the 2DEG properties Applied Physics Letters, Vol. 125, Article 123505 (Article in journal) Continue to DOI
Viktor Rindert, Steffen Richter, Philipp Kuhne, Alexander Ruder, Vanya Darakchieva, Mathias Schubert (2024) Bloch equations in terahertz magnetic-resonance ellipsometry Physical Review B, Vol. 110, Article 054413 (Article in journal) Continue to DOI
He Zhang, Xing Xing, Nerijus Armakavicius, Hong Meng (2024) Self-powered, multi-angle gas flow sensing based on photovoltaics with porous graphite electrodes Sensors and Actuators A-Physical, Vol. 378, Article 115754 (Article in journal) Continue to DOI
Nerijus Armakavicius, Philipp Kuhne, Alexis Papamichail, Hengfang Zhang, Sean Robert Knight, Axel Persson, Vallery Stanishev, Jr-Tai Chen, Plamen Paskov, Mathias Schubert, Vanya Darakchieva (2024) Electronic Properties of Group-III Nitride Semiconductors and Device Structures Probed by THz Optical Hall Effect Materials, Vol. 17, Article 3343 (Article in journal) Continue to DOI
Balasubramanian Sundarapandian, Dat Tran, Lutz Kirste, Patrik Stranak, Andreas Graff, Mario Prescher, Akash Nair, Mohit Raghuwanshi, Vanya Darakchieva, Plamen Paskov, Oliver Ambacher (2024) Comparison of aluminum nitride thin films prepared by magnetron sputter epitaxy in nitrogen and ammonia atmosphere Applied Physics Letters, Vol. 124, Article 182101 (Article in journal) Continue to DOI
Ragnar Ferrand-Drake Del Castillo, Ding-Yuan Chen, Jr-Tai Chen, Mattias Thorsell, Vanya Darakchieva, Niklas Rorsman (2024) Characterization of Trapping Effects Related to Carbon Doping Level in AlGaN Back-Barriers for AlGaN/GaN HEMTs IEEE Transactions on Electron Devices (Article in journal) Continue to DOI
Anders Gustafsson, Axel Persson, Per O A Persson, Vanya Darakchieva, Zhaoxia Bi, Lars Samuelson (2024) Cathodoluminescence investigations of dark-line defects in platelet-based InGaN nano-LED structures Nanotechnology, Vol. 35, Article 255703 (Article in journal) Continue to DOI
Daniela Gogova-Petrova, Dat Tran, Vallery Stanishev, Valdas Jokubavicius, L. Vines, M. Schubert, Rositsa Yakimova, Plamen Paskov, Vanya Darakchieva (2024) High crystalline quality homoepitaxial Si-doped β-Ga2O3(010) layers with reduced structural anisotropy grown by hot-wall MOCVD Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, Vol. 42, Article 022708 (Article in journal) Continue to DOI
Nerijus Armakavicius, Sean Robert Knight, Philipp Kuhne, Vallery Stanishev, Dat Tran, Steffen Richter, Alexis Papamichail, Megan Stokey, Preston Sorensen, Ufuk Kilic, Mathias Schubert, Plamen P. Paskov, Vanya Darakchieva (2024) Electron effective mass in GaN revisited: New insights from terahertz and mid-infrared optical Hall effect APL Materials, Vol. 12, Article 021114 (Article in journal) Continue to DOI
Sean Robert Knight, Steffen Richter, Alexis Papamichail, Megan Stokey, Rafal Korlacki, Vallery Stanishev, Philipp Kuhne, Mathias Schubert, Vanya Darakchieva (2024) Terahertz permittivity parameters of monoclinic single crystal lutetium oxyorthosilicate Applied Physics Letters, Vol. 124, Article 032101 (Article in journal) Continue to DOI

Research

Colaborations

International

  • Prof. M. Schubert, University of Nebraska-Lincoln, USA
  • Prof. N. Grandjean, EPFL, Switzerland
  • Dr. S. Ruffenach, University of Montpellier, France
  • Prof. K. Kishino, Sofia University, Japan
  • Prof. W. J. Schaff, Cornell University, USA
  • Prof. Y. Nanishi, Retsumeikan University, Japan
  • Dr. T. Monteiro, University of Aveiro, Portugal
  • Prof. L.-C. Cheng, National Taiwan University, Taiwan
  • Prof. A. Yoshikawa, Chiba University, Japan
  • Prof. E. Valcheva, Sofia University, Bulgaria.
  • Prof. L. W. Tu, National Sun Yat-Sen University, Taiwan
  • Dr. H-W. Becker, Rhur University, Germany
  • Dr. K. Lorenz, ITN/IST, Portugal
  • Dr. A. Tiberj, University of Montpellier 2, France

Industrial collaborations

  • Dr. T. Tiwald, Dr. G. Hertzinger and Prof. J. Woollam, J.A. Woollam Co , USA - ellipsometry equipment and software
  • Dr. O. Kordina, SweGaN AB, Sweden - AlGaN, HEMTs
  • Dr. F. Allerstam, On Semiconductor, USA - high-frequency electronics
  • Dr. C.-Y. Chen, ABB, Sweden - high power electronics
  • Dr. M. Higashiwaki, Tamura Co., Japan - Ga2O3
  • Prof. R. Yakimova, Graphensic AB, Sweden - graphene
  • Prof. A. Usui, Furukawa Co., Ltd., Japan - bulk GaN

Internal

  • Prof. H. Zirath and Dr. N. Rorsman, Chalmers University - electronic devices
  • Prof. R. Yakimova - graphene
  • Dr. F. Tasnadi - ab initio calculations
  • Prof. J. Birch - novel nitride alloys
  • Dr. P. Persson - TEM
  • Prof. E. Janzen - HEMTs
  • Dr. A. Kakanakova - AlN and AlGaN
  • Prof. B. Monemar - PL and InN

External media

Chapter on Phonon Properties published in book Gallium Oxide

In this chapter, written by members of our team we present and discuss the complete set of infrared-active phonon modes in monoclinic-symmetry crystal modification gallium oxide. This chapter attempts to summarise the current state of knowledge about the optical phonon mode propoerties and their coupling with free charge carriers in gallium oxide with monoclinic crystal structure.

You can find the book at springer.com.

April 2019 - Inside front cover in Journal of Materials Chemistry C

Our paper on the anomalous optical conductivity dispersion of electrically conducting polymers determiend by ultra-wide spectral range ellipsometry combined with a Drude-Lorentz model is selected as inside front cover in the April issue of Journal of Materials Chemistry C.

J. Mater. Chem. C, 2019,7, 4350-4362.

April 2019 - Eva Bittrich from Leibniz Institute of Polymer Research Dresden is visiting

Eva Bittrich from Leibniz Institute of Polymer Research Dresden is visiting THeMAC for a week. She is working on applying far-infrared and terahertz spectroscopic ellipsometry to study the H-bonding in thin polycristalline films of ellagic acid and other semiconducting films of small organic molecules. Eva presented a Faculty seminar on Nanostructured organic thin films for biosensing and energy harvesting. We are looking forward to this new exciting collaboration in polymer research.

READ MORE



Contact

Student projects

Student project

Recently Shiqui Guo has joined our group. He will spend the next few months (spring term 2021) working on his Bachelor project on graded AlGaN HEMTs. He will work closely with Ph.D. student Alexis Papamichail and focus on the characterization of the HEMTs.

Organisation