A5006915353- ZnO doping and properties
- Semiconductor Quantum Structures and Devices
- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Ga2O3 and related materials
- Semiconductor materials and interfaces
- Advanced Chemical Physics Studies
- Advanced Semiconductor Detectors and Materials
- Surface and Thin Film Phenomena
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Heusler alloys: electronic and magnetic properties
- Graphene research and applications
- Quantum and electron transport phenomena
- Metal and Thin Film Mechanics
- Advanced Condensed Matter Physics
- Gas Sensing Nanomaterials and Sensors
- Topological Materials and Phenomena
- Advanced Thermoelectric Materials and Devices
- Copper-based nanomaterials and applications
- Perovskite Materials and Applications
- Silicon Nanostructures and Photoluminescence
- Chalcogenide Semiconductor Thin Films
- Silicon Carbide Semiconductor Technologies
- Ion-surface interactions and analysis
Polish Academy of Sciences
2014-2024
Institute of Physics
2011-2022
Czech Academy of Sciences, Institute of Physics
1974-2020
Kazimierz Wielki University in Bydgoszcz
2012-2018
University of Bydgoszcz
2009-2018
North Carolina State University
1996-2012
Institute of Electron Technology
2010
Institute of Molecular Physics of the Polish Academy of Sciences
2010
University of Notre Dame
1993
École Polytechnique Fédérale de Lausanne
1984-1989
We present a combined theoretical and experimental study of the ferromagnetic semiconductor (Ga,Mn)As which explains remarkably large changes observed on low-temperature annealing. Careful control annealing conditions allows us to obtain samples with transition temperatures up 159 K. Ab initio calculations, in situ Auger spectroscopy, resistivity measurements during show that are due out diffusion Mn interstitials towards surface, governed by an energy barrier 0.7-0.8 eV. Electric fields...
The results of an extensive theoretical study native defects in hexagonal GaN are presented. We have considered cation and anion vacancies, antisites, interstitials. computations were carried out using ab initio molecular dynamics supercells containing 72 atoms. N vacancy introduces a shallow donor level, may be responsible for the n-type character as-grown GaN. Due to wide gap nitrides, self-compensation effects strongly reduce both p-type doping efficiencies due formation gallium...
We analyze optical absorption, transmission, luminescence, and Raman scattering in $n$-type GaN at hydrostatic pressures up to 30 GPa. The results show freeze-out of free electrons above $\ensuremath{\sim}20\mathrm{GPa}$ due trapping levels that are resonant ambient pressure but become gap states high pressures. Ab initio calculations both the N vacancy Ga interstitial undergo this transition $\ensuremath{\sim}20\mathrm{GPa}$, should be more abundant. dependence yellow luminescence indicates...
Doping properties of substitutional C, Si, and Ge impurities in wurtzite GaN AlN were studied by quantum molecular dynamics. We considered incorporation on both cation anion sublattices. When substituting for cations, Si are shallow donors GaN, while becomes a deep donor AlN. Both acceptors the N site. Substitutional C${}_{\mathrm{cation}}$ is but one AlN; C${}_{\mathrm{N}}$ relatively acceptor materials. Two effects that potentially quench doping efficiency investigated. The first...
Electronic structure and formation energies of substitutional carbon impurities in hexagonal GaN AlN were studied by quantum molecular dynamics. Substitutions on both cation anion sites considered. Ccation is a shallow donor, while CN acceptor. A DX-like configuration metastable for CGa CAl0, stable CAl−. The solubility excellent, but it accompanied efficient self-compensation acceptors donors. This due to two factors: (i) the large energy gain induced electron transfer from CN, which close...
The binding sites and diffusion barriers for a Si adatom moving over buckled Si(100) surface single-height steps were calculated using ab initio methods. Surprisingly, the may be sensitive to local buckling of dimers. energies escape at step edges depend strongly on type step. ${S}_{A}$ edge is relatively poor sink adatoms, while adatoms can easily trapped ${S}_{B}$ edge. These results explain fast growth observed ends dimer rows.
Electronic, magnetic, and structural properties of several ${II}^{A}\text{\ensuremath{-}}V$ compounds are analyzed using ab initio calculations. We consider four crystal structures: zinc-blende, NiAs, rocksalt, ${\mathrm{Zn}}_{3}{\mathrm{P}}_{2}$. Our results indicate that nitrides in the rocksalt phase stable ferromagnetic half-metals characterized by total spin polarization free holes valence band. The previously considered zinc-blende II-V crystals is as well, but less about...
Doping properties of Ag in ZnO were analyzed by first-principles calculations within both the local-density and generalized gradient approximations. The ionization energy ${\text{Ag}}_{\text{Zn}}$, about 0.2 eV, is comparable to that commonly used group-V acceptors, lower than two other ${\text{I}}^{\text{B}}$ species, Cu Au. Formation favorable O-rich conditions 0.85 which corresponds solubility limit ${10}^{18}\text{ }{\text{cm}}^{\ensuremath{-}3}$ at $700\text{...
Abstract Relaxation times for elastic electron scattering in the symmetry‐induced zero‐gap semi‐conductors of zincblende structure are calculated, taking into account nonparabolic character conduction band both density states and wave functions. The calculation is based on proposed by Groves Paul uses exact k · p solutions three‐level model Γ 8 , 6 7 levels. Electron charged impurities heavy holes, optical phonons (screened polar interaction) acoustic considered. Spin‐flip transitions play...
The $s,p-d$ exchange coupling between the spins of band carriers and transition metal (TM) dopants ranging from Ti to Cu in ZnO is studied within density functional theory. $+U$ corrections are included reproduce experimental gap dopant levels. $p-d$ reveals unexpectedly complex features. In particular, (i) constants $N_0\beta$ vary about 10 times when going V Cu, (ii) not only value but also sign depends on charge state dopant, (iii) with heavy holes light same; case Fe, Co Ni, $N_0\beta$s...
Electronic structure of GaAs with a 3% addition B and N is studied by ab initio molecular dynamics. We find that the influence on band gap its pressure dependence weaker than N. Hydrostatic strongly reduces oscillator strength fundamental transition in GaAs:B, but not GaAs:N. Group-theoretical analysis shows differences are symmetry induced, stem from different substitution sites (cation sublattice) (anion sublattice). For both alloys we an additional optical at about 0.5 eV above involving...
We report on measurements of the hole density, ferromagnetic transition temperature TC, and magnetization in a series as-grown annealed (Ga,Mn)As samples. Estimating fraction incorporated Mn occupying interstitial substitutional sites allows direct comparison predictions mean field theory with experiment, determination magnetic moment per Mn. The saturation TC at high concentration is consistent prediction. estimated close to expected 5μB for all samples studied if an antiferromagnetic...
High spin states of cation vacancies in GaP, GaN, AlN, BN, ZnO and BeO were analyzed by first principles calculations. The spin-polarized vacancy-induced level is located the band gap BeO. In nitrides, stronger exchange coupling forces vacancy to be resonant with valence bands, forbids formation positively charged GaN allows Al p-AlN assume highest possible S=2 state. shape density, isotropic zinc blende structure, has a pronounced directional character wurtzite structure. Stability...
The atomic and electronic structure of the stepped Si(001) surface is investigated by ab initio molecular dynamics. All configurations considered us are unstable with respect to buckling dimers. ground state reconstruction depends on type step and, in some cases, different from that flat surface. observed differences between filled-state empty-state scanning tunneling microscopy images due wave function shapes rather than tip-induced reconstruction.
Density functional theory (DFT) calculations of the electronic structure Pb${}_{1\ensuremath{-}x}$Mn${}_{x}$Te were performed using OpenMX package with fully relativistic pseudopotentials. Because underestimation band gap in DFT, ``bare'' DFT give a wrong order bands at $L$ point. Correct structures both PbTe and as well correct pressure coefficients fundamental are obtained by tuning strength spin-orbit coupling for $6p$(Pb) orbitals. The results confirm critical role valence maximum...
Nitrogen doping of a carbon nanoribbon is profoundly affected by its one-dimensional character, symmetry, and interaction with edge states. Using state-of-the-art ab initiocalculations, including hybrid exact-exchange density functional theory, we find that, for N-doped zigzag ribbons, the electronic properties are strongly dependent upon sublattice effects due to non-equivalence two sublattices. For armchair N-doping different depending ribbon family: families 2 0, N-induced levels in...
Structural properties of ZnTe, MnTe, and Mn 1-x Zn x Te alloy with zinc--blende, NiAs, wurtzite phases were investigated by ab initio calculations.The calculated structural are in good agreement the available experimental data.Theory predicts that zinc-blende phase is more stable than for all compositions.Mn1-xZnxTe samples 0.01 < 0.20 grown MBE.X-ray analysis their crystalline structure revealed presence zinc-blende, wurtzite, NiAs phases.The dominant changes from sample = to 0.20.The...
Self-consistent pseudopotential calculations indicate that the lattice-mismatched (GaP${)}_{1}$(InP${)}_{1}$, (GaAs${)}_{1}$(InAs${)}_{1}$, and (GaAs${)}_{1}$(GaSb${)}_{1}$ [001] bulk monolayer superlattices are unstable against phase segregation at zero temperature. Compared to case of lattice-matched (GaAs${)}_{1}$(AlAs${)}_{1}$ (CdTe${)}_{1}$(HgTe${)}_{1}$ [001], instability is much stronger has a different origin, namely excess elastic energy distorted bonds. Epitaxial growth on...
Formation of vacancy-interstitial Frenkel pairs, together with the properties interstitials and vacancies in CdTe, ZnTe, their alloys were investigated by first-principles calculations. Generation pairs on cation sublattice strongly depends Fermi energy: presence excess free electrons reduces energy barrier for pair generation from 2.5 eV intrinsic samples to 1.2 eV. Moreover, ${E}_{F}$ determines both stability respect recombination binding energy, which varies $\ensuremath{\sim}0.2$...
Dopants of transition metal ions in II-VI semiconductors exhibit native 2+ valency. Despite this, 3+ or mixed 3+/2+ valency iron ZnO was reported previously. Several contradictory mechanisms have been put forward for explanation this fact so far. Here, we analyze Fe by complementary theoretical and experimental studies. Our calculations within the generalized gradient approximation (GGA+U) indicate that ion is a relatively shallow donor. Its stable charge state Fe2+ ideal ZnO, however, high...
The segregation of Ge during growth on SiGe(001) surfaces was investigated by ab initio calculations. Four processes involving adatoms rather than ad-dimers were considered. two most efficient channels proceed the concerted exchange mechanism and involve a swap between an incorporated Si adatom, or in first second surface layers, respectively. calculated activation energies approximately 1.5 eV explain well high-temperature experimental data. Segregation mechanisms step edges are much less efficient.