Prof. Dr. Witold Trzeciakowski
Institute of High Pressure Physics, Polish Academy of Sciences
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Academic Career Length
45Years (1982-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications15 August 1991 in Physical Review B
Journal Article
Witold TrzeciakowskiMGMassimo Gurioli
Massimo Gurioli
In the presence of an electric field the energy spectrum of a quantum well becomes continuous, with bound states transforming into resonances, but also with strong modifications in the above-barrier region. Analyzing the density of states (DOS) of the system, we find modulated oscillations of this quantity due to interference of the waves reflected from the well boundaries and from the slope of the electric-field potential. We show that these oscillations in DOS are related to the Fowler-Nordheim resonances in transmission through a double-barrier tunneling structure. We also calculate the absorption α(ħω) from the ground state in the well to the energy continuum above the barriers. We find a pronounced electric-field effect on α(ħω); the slowly varying curve for zero field transforms into a series of sharp peaks. The observation of these peaks requires narrow wells, wide barriers, and moderate electric fields. It would allow for the determination of important parameters like band offset or the value of the internal electric field.
15 August 1988 in Physical Review B
Journal Article
Witold TrzeciakowskiThe interface between two one-dimensional crystals is studied with the use of the transfer matrix. This microscopic approach allows a study of the accuracy of the effective-mass approximation (EMA) and derivation of the boundary conditions (BC) for the envelope functions. These BC turn out to be very different from those adopted so far: they contain an additional microscopic parameter (independent of the effective masses) which characterizes the interface and may be as important as the band offset. It is shown that it is not possible to generalize the EMA to abrupt heterojunctions. When the band edges on two sides of the interface are of different types (as in GaAs/AlAs), the BC are unusual and can lead to the existence of interface states and also to a strong modification of the bound states in a single quantum well.
11 January 2021 in Optics Express
Journal Article
KPK. Pieniak
K. Pieniak
MCMikołaj Chlipała
Mikołaj ChlipałaHTH. Turski
H. Turski
Witold TrzeciakowskiGMG. Muziol
G. Muziol
TSTadeusz Suski
Tadeusz Suski +6
Nitride-based light-emitting diodes (LEDs) are well known to suffer from a high built-in electric field in the quantum wells (QWs). In this paper we determined to what extent the electric field is screened by injected current. In our approach we used high pressure to study this evolution. In LEDs with a narrow QW (2.6 nm) we found that even at a high injection current a large portion of built-in field remains. In LEDs with very wide QWs (15 and 25 nm) the electric field is fully screened even at the lowest currents. Furthermore, we examined LEDs with a tunnel junction in two locations – above and below the active region. This allowed us to study the cases of parallel and antiparallel fields in the well and in the barriers.
Journal Article
BSBarbara Sterczała
Barbara Sterczała
Kinga Grzech-LeśniakOMOlga Michel
Olga MichelWitold Trzeciakowski
Marzena Dominiak
Kamil JurczyszynPurpose: to assess the effect of photobiomodulation (PBM) on human gingival fibroblast proliferation. Methods: The study was conducted using the primary cell cultures of human fibroblasts collected from systemically healthy donors. Three different laser types, Nd:YAG (1064 nm), infrared diode laser (980 nm), and prototype led laser emitting 405, 450, and 635 nm were used to irradiate the fibroblasts. Due to the patented structure of that laser, it was possible to irradiate fibroblasts with a beam combining two or three wavelengths. The energy density was 3 J/cm2, 25 J/cm2, 64 J/cm2. The viability and proliferation of cells were determined using the (Thiazolyl Blue Tetrazolium Blue) (MTT) test conducted 24, 48, and 72 h after laser irradiation. Results: The highest percentage of mitochondrial activity (MA = 122.1%) was observed in the group irradiated with the 635 nm laser, with an energy density of 64 J/cm2 after 48 h. The lowest percentage of MA (94.0%) was observed in the group simultaneously irradiated with three wavelengths (405 + 450 + 635 nm). The use of the 405 nm laser at 25 J/cm2 gave similar results to the 635 nm laser. Conclusions: The application of the 635 nm and 405 nm irradiation caused a statistically significant increase in the proliferation of gingival fibroblasts.
15 December 1988 in Physical Review B
Journal Article
Witold TrzeciakowskiThe effective-mass method (EMM) has been widely used for the description of layered semiconductor structures with sharp boundaries (quantum wells, superlattices, etc.), although it does not work for rapidly varying potentials. Here, I analyze the EMM in a simple case of one-dimensional heterostructures. Being able to obtain the exact solutions (using the transfer-matrix method), I can extract from them the envelope functions within the one-band or multiband EMM. I can then derive the boundary conditions (BC’s) for these envelopes at the interfaces. These BC’s turn out to be very different from what has been adopted so far. They involve microscopic parameters of the bulk materials forming the layered structures; these parameters cannot be expressed by the effective masses or other band-structure characteristics. In the multiband case the BC’s are energy dependent. For the band edges of different types on two sides of the interface (as in GaAs/AlAs or Si/Ge), the BC’s are unusual and allow for the existence of intrinsic interface states. I also point out some artifacts of the EMM; unphysical solutions in the bands and in the gaps which should be rejected.
22 July 2005 in Applied Physics Letters
Journal Article
GFG. Franssen
G. Franssen
TST. Suski
T. Suski
Perlin PiotrRBR. Bohdan
R. Bohdan
BABercha Artem
Bercha ArtemSKS. Kokenyesi
S. Kokenyesi
+6
Photocurrent spectroscopy and hydrostatic-pressure-dependent electroluminescence are used to show that heavy Si doping of quantum barriers is sufficient to achieve full screening of polarization-induced electric fields (PIEFs) in nitride light emitting diodes (LEDs) and laser diodes (LDs) with InGaN quantum wells. Furthermore, it is shown that at currents close to lasing threshold in nitride LDs injected charge alone is sufficient to achieve full screening of PIEFs. In contrast, full screening at low currents can only be accomplished via Si doping of quantum barriers.
About Me
Witold Trzeciakowski was born in Warsaw, Poland in 1952. He obtained M.Sc. degree in Solid-State Physics, Warsaw University in 1974. He received his Ph.D. at the Faculty of Physics, Warsaw University in 1980. In 1989 he received the degree of "habilitation" from the Institute of Physics, Polish Academy of Sciences and in 2000 the title of Professor of Physics.
He worked from 1974 till 1980 as a teaching assistant at the Faculty of Physics, Warsaw University and then moved to the Institute of High Pressure Physics, Polish Academy of Sciences where he has been working until now. In 1983 he spent a few months at the High Magnetic Field Laboratory in Grenoble (France), in 1986-1988 he worked as a research associate at the National Research Council (Ottawa, Canada), in 1989 he spent 3 months at State University of New York (Buffalo, USA), in 1991-1992 at the LENS laboratory at the University of Florence (Italy), in 1993-1994 at the IXL laboratory of the Bordeaux University (France) and in 1996-1997 he was a visiting professor at the Department of Physics, University of Valencia (Spain). He participated in two European Projects and in one NATO research project.
His main scientific activity was in semiconductor physics, both theoretical and experimental. His recent research concerned laser diode physics, including using pressure for wavelength tuning, and the application of laser diodes in dermatology.