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Laboratory of Electronic Processes

Head of department prof., habil. dr. Steponas Ašmontasprof., habil. dr. S. Ašmontas
phone +370 5 2627124

The main activities are concentrated on:
  • Investigation of interaction of electromagnetic radiation with semiconductor nanostructures;
  • Investigation of optical transitions in semiconductor nanostructures using single photon counting method;
  • Theoretical modeling of charge carrier spin transport in semiconductor nanostructures;
  • Modeling of noise, emission and detection of electromagnetic radiation in semiconductor structures by means of Monte Carlo method;
  • Development of innovative devices for microwave and terahertz electronic, quantum electronic and spintronic applications.

But the main value and achievement is experience. The scientists of the Laboratory are excellent experts in:

  • Monte Carlo modeling noise and radiation emission and detection in semiconductor structures,
  • solving Maxwell‘s equations in microwave waveguide systems,
  • investigation of carrier transport in sophisticated semiconductor systems,
  • study of hot carrier phenomena in solid-state structures.

 


Equipment
Scalar network analyzers produced by Elmika Ltd allow investigating interaction of microwave radiation with semiconductor structures in the frequency range from 10 GHz up to 170 GHz.
   

Agilent Semiconductor Parameter Analyzer and LCR meter are used for I-V and C-V measurements of semiconductor structures.

 
Agilent Spectrum Analyzer is used to investigate electromagnetic radiation of 20 kHz ÷ 325 GHz frequency range generated by semiconductor structures.
 
Karl Suess and Cascade Microtech probe stations are used for measurements of semiconductor electric parameters in DC regime and at high frequencies of 26÷40 GHz and 75÷110 GHz ranges. 
   
Original near field microwave microscope produced in collaboration with Elmika Ltd is used to investigate electrical properties of materials having various electrical conductivity values, from dielectrics up to metals. The microscope operates in millimeter wavelengths of electromagnetic radiation.
 
Low temperature photoluminescence setup with two photon counting systems. It is possible to register a continuous flow and optical pulses of picosecond duration at low 200-900 nm light intensity in the temperature range 4-300 K with 0.008 nm spectral resolution (or 0.003 nm resolution up to 750 nm wavelength): a) time correlated single photon counting module allows to measure photoluminescence decay, photon correlation and time resolved luminescence spectra in the range from 10 ps up to 2 µs; b) gated photon counter allows to measure photoluminescence spectra and their decay over 250 ns.
 
Liquid phase epitaxy equipment is used to fabricate various semiconductor structures serving as a base of microwave , infrared and x-ray radiation sensors as well as solar cells developed in the Department of Electronics. 
   
Microelectronics technological facility is used for fabrication of experimental semiconductor electronic devices at small extent.
 
Dektak 6M stylus profilometer for sample surface topography measurements in the nano scale. It allows to measure vertical dimensions of the surface with few nanometer accuracy. 
   
Optical parametric oscillator (λ=1.4÷4.2 µm), optically pumped by Nd:YAG laser radiation (λ=1.06 µm, pulse duration ~10 ns (Ekspla Ltd)
 
Tuned wavelength CO2 laser (λ=9.2÷10.8 µm). Power in CW regime 20-40 W. Pulse power 2-5 kW at pulse duration ~150 ns (Edinburgh Instruments Ltd).
 
Optically pumped far-infrared laser of tunable wavelength, operating in CW and pulsed regime and emitting over 50 discrete lines of λ ~ 50 - 700 μm (respectfully, ƒ ~ 6 – 0,4 THz) spectrum range (Edinburgh Instruments Ltd.).
projects
  • Project "Development of novel solar cell forming technology using thin graded‐gap porous Si structures with embedded plasmic metal nanoparticles and electrostatically charged ferroelectric layer" financed by the Research Council of Lithuania within Lithuanian‐Ukrainian program; led by S. Ašmontas, contract No. TAP LU‐5‐2016, duration 2016 – 2017. Porous silicon layer containing nanometric structures will be formed by means of electrochemical etching and intense laser light. Graded forbidden energy gap is typical for such nano structures; this way it will extend the range of usefully absorbed light and thereby the unwanted effects of hot electrons reducing solar cell efficiency will be weakened. Also, to increase the absorption of sunlight, plasmic metal nanoparticles will be embedded in the surface of porous silicon.

  • The project „New broadband sensors of elektromagnetic radiation on the on the base of 2DEG“ in the frame of Scientific Programme of Lithuanian Science Council „Towards Future Technologies“ is implemented in 2016-2018. The implementation of the LTDEP project will: 1) put light on the electromagnetic radiation detection mechanism in the asymmetrical field‐transistor‐like structure with the partial gate over the two‐dimensional electron channel; 2) on the base of these structures, give impulse to develop high‐sensitivity sensor; 3) extend the detectable radiation range up to the X‐ray region.

Most important publications
  1. Bulat L. P., Novotelnova A. V., Tukmakova A. S., Yerezhep D. E., Osvenskii V. B., Sorokin A. I., Panchenko V. P., Bochkov L. V., Ašmontas Steponas. Simulation of SPS process for fabrication of thermoelectric materials with predicted properties. Journal of electronic materials. ISSN 0361-5235. 2018, vol. 47, iss. 2, p. 1589-1594.
  2. Gric Tatjana. Hess, Ortwin. Long-range surface plasmons supported by the disordered nanowire metamaterials. Journal of electromagnetic waves and applications. ISSN 0920-5071. eISSN 1569-3937. 2018, vol. 32, iss. 6, p. 750-757.
  3. Gric Tatjana, Hess Ortwin. Surface waves supported by the nanostructured semiconductor metamaterials. Journal of electromagnetic waves and applications. ISSN 0920-5071. eISSN 1569-3937. 2018, vol. 32, iss. 5, p. 591-600.
  4. Gradauskas Jonas, Stupakova Jolanta, Sužiedėlis Algirdas, Ašmontas Steponas, Maneikis Andrius, Samuolienė Neringa. Doping influence on microwave detection by metal–porous silicon contacts. Applied physics. A, Materials science & processing. ISSN 0947-8396. 2018, vol. 124, iss. 5, art. no. 352, p. 1-5.
  5. Steponas Ašmontas, Romas Raguotis, Skaidra Bumelienė. Monte Carlo study of impact ionization in n‑type InAs induced by intense ultrashort terahertz pulses. Optical and quantum electronics. ISSN 0306-8919. 2018, vol. 50, iss. 6, art. no. 264, p. 1-9.
  6. Gric Tatjana, Hess Ortwin. Investigation of hyperbolic metamaterials. Applied sciences. ISSN 2076-3417. 2018, vol. 8, iss. 8, art. no. 1222, p. 1-16.
  7. Trofimov Aleksej, Gric Tatjana. Surface plasmon polaritons in hyperbolic nanostructured metamaterials. Journal of electromagnetic waves and applications. ISSN 0920-5071. 2018, vol. 32, iss. 14, p. 1857-1867.
  8. Steponas Ašmontas, Jonas Gradauskas, Algirdas Sužiedėlis, Aldis Šilėnas, Edmundas Širmulis, Vitas Švedas, Viktoras Vaičikauskas, Ovidijus Alfonsas Žalys. Hot carrier impact on photovoltage formation in solar cells. Applied physics letters. ISSN 0003-6951. 2018, vol. 113, iss. 7, art. no. 071103, p. 1-3.
  9. Gric Tatjana, Gorodetsky Andrei, Trofimov Aleksej, Rafilov Edik. Tunable plasmonic properties and absorption enhancement in terahertz photoconductive antenna based on optimized plasmonic nanostructures. Journal of infrared, millimeter, and terahertz waves. ISSN 1866-6892.2018, vol. 39, iss. 10, p. 1028-1038.
  10. Diachenko O.V., Dobrozhan O.A., Opanasyuk A.S., Ivashchenko M.M., Protasova T.O., Kurbatov D.I., Čerškus Aurimas. The influence of optical and recombination losses on the efficiency of thin-film solar cells with a copper oxide absorber layer. Superlattices and microstructures. ISSN 0749-6036. 2018, vol. 122, p. 476-485.
  11. Čerškus Aurimas, Sužiedėlis Algirdas, Lučun Andžej, Anbinderis Maksimas, Gradauskas Jonas, Šutinys Ernestas. Photoluminescence peculiarities of epitaxial structure with 2DEG layer designed for microwave detectors. Applied physics A. Materials science & processing. ISSN 0947-8396. 2018, vol. 124, iss. 11, art. no. 742, p. 1-6.
  12. Acus Artūras, Dargys Adolfas. The inverse of a multivector: beyond the threshold p + q = 5. Advances in applied Clifford algebras. ISSN 0188-7009. 2018, vol. 28, no 3, art. no 65, p. 1-20.
  13. Gric Tatjana, Trofimov Aleksej, Hess Ortwin. Manipulating surface plasmon polaritons with nanostructured TCO metamaterials. Journal of electromagnetic waves and applications. ISSN 0920-5071. 2019, vol. 33, iss. 4, p. 493-503.
  14. Trofimov Aleksej, Gric Tatjana, Hess Ortwin. Three-layered nanostructured metamaterials for surface plasmon polariton guiding. Journal of mathematical chemistry. ISSN 0259-9791. 2019, vol. 57, iss. 1, p. 190-201.
  15. Adomaitienė Elena, Bumelienė Skaidra, Tamaševičius Arūnas Vytautas. Suppressing synchrony in an array of the modified FitzHugh–Nagumo oscillators by filtering the mean field. Journal of applied physics. ISSN 0021-8979. 2019, vol. 125, art. no. 104902, p. 1-6.