Konrad Sakowski
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View article: Fundamentals of Metal Contact to p-Type GaN—A New Multilayer Energy-Saving Design
Fundamentals of Metal Contact to p-Type GaN—A New Multilayer Energy-Saving Design Open
The electrical properties of contacts to p-type nitride semiconductor devices, based on gallium nitride, were simulated by ab initio and drift-diffusion calculations. The electrical properties of the contact are shown to be dominated by th…
View article: Ab Initio Elucidation of the Nature of the Bonding of Tetrahedral Nitrides (BN, AlN, GaN, and InN), Hexagonal BN, and Graphene
Ab Initio Elucidation of the Nature of the Bonding of Tetrahedral Nitrides (BN, AlN, GaN, and InN), Hexagonal BN, and Graphene Open
Recent measurements of the band properties of AlN and GaN by fluorescence yield absorption and soft X-ray emission spectroscopies revealed that their valence band (VB) is composed of two separate subbands. The upper VB subband of GaN is co…
View article: Fast non-equilibrium carrier dynamics in polar InGaN/GaN structures with wide quantum wells
Fast non-equilibrium carrier dynamics in polar InGaN/GaN structures with wide quantum wells Open
We analyze the time-resolved photoluminescence (PL) from the bulklike continuum of excited states of 450 nm emitting InGaN/GaN device structures that are based on wide quantum wells with 25 nm thickness. In its spectrally integrated form, …
View article: Spontaneous and Piezo Polarization Versus Polar Surfaces: Fundamentals and Ab Initio Calculations
Spontaneous and Piezo Polarization Versus Polar Surfaces: Fundamentals and Ab Initio Calculations Open
In this study, the fundamental properties of spontaneous and piezo polarization and surface polarity were defined. It was demonstrated that the Landau definition of polarization as a dipole density could be used in infinite systems. Differ…
View article: The Photoionization Processes of Deep Trap Levels in n-GaN Films Grown by MOVPE Technique on Ammono-GaN Substrates
The Photoionization Processes of Deep Trap Levels in n-GaN Films Grown by MOVPE Technique on Ammono-GaN Substrates Open
In this paper, we present various theoretical models that accurately approximate the spectral density of the optical capture cross-section (σe0) obtained through the analysis of photo-capacitance transients using the deep-level optical spe…
View article: Coulomb Contribution to Shockley–Read–Hall Recombination
Coulomb Contribution to Shockley–Read–Hall Recombination Open
A nonradiative recombination channel is proposed, which does not vanish at low temperatures. Defect-mediated nonradiative recombination, known as Shockley–Read–Hall (SRH) recombination, is reformulated to accommodate Coulomb attraction bet…
View article: Polarization spontaneous and piezo: fundamentals and their implementation in ab initio calculations
Polarization spontaneous and piezo: fundamentals and their implementation in ab initio calculations Open
Fundamental properties of spontaneous and piezo polarization are reformulated and critically reviewed. It was demonstrated that Landau definition of polarization as a dipole density could be used to the infinite systems. The difference bet…
View article: Graphene Schottky barrier diode acting as a semi-transparent contact to n-GaN
Graphene Schottky barrier diode acting as a semi-transparent contact to n-GaN Open
In this letter, we demonstrate the successful development of graphene Schottky barrier diodes (Gr SBDs), which act as an efficient semi-transparent contact to n-GaN. We show that Gr SBDs can be used for deep trap investigations in n-GaN by…
View article: Augmentation of the electron counting rule with Ising model
Augmentation of the electron counting rule with Ising model Open
The stability of a mixture of two different surface reconstructions is investigated focusing on GaN(0001) surface mixed with Gaad(2×2) and 3Ga-H(2×2) domains using the density functional theory calculations. Since the number of candidate s…
View article: Regional patient transfer patterns matter for the spread of hospital-acquired pathogens
Regional patient transfer patterns matter for the spread of hospital-acquired pathogens Open
Pathogens typically responsible for hospital-acquired infections (HAIs) constitute a major threat to healthcare systems worldwide. They spread via hospital (or hospital-community) networks by readmissions or patient transfers. Therefore, k…
View article: Coulomb contribution to Shockley-Read-Hall (SRH) recombination
Coulomb contribution to Shockley-Read-Hall (SRH) recombination Open
Defect-mediated nonradiative recombination, known as Shockley-Read-Hall (SRH) recombination is reformulated. The introduced model considers Coulomb attraction between charged deep defect and the approaching free carrier, showing that this …
View article: Incorporation of indium into GaN layers in the context of MOVPE thermodynamics and growth – Ab initio studies
Incorporation of indium into GaN layers in the context of MOVPE thermodynamics and growth – Ab initio studies Open
Indium incorporation on the GaN surface (0001) has been analyzed in the context of InGaN growth by Metal Organic Vapor Phase Epitaxy (MOVPE). To understand phenomena at the atomic level, calculations based on Density Functional Theory (DFT…
View article: Patient transfer patterns and the spread of hospital-acquired infections in subnetworks of a country: an example of federal states in Germany
Patient transfer patterns and the spread of hospital-acquired infections in subnetworks of a country: an example of federal states in Germany Open
Pathogens typically responsible for hospital-acquired infections (HAIs) constitute a major threat to healthcare systems worldwide. They spread via hospital (or hospital-community) networks by readmissions or patient transfers. Therefore, k…
View article: Polarization Doping in a GaN-InN System—Ab Initio Simulation
Polarization Doping in a GaN-InN System—Ab Initio Simulation Open
Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The emergi…
View article: Polarization doping—<i>Ab initio</i> verification of the concept: Charge conservation and nonlocality
Polarization doping—<i>Ab initio</i> verification of the concept: Charge conservation and nonlocality Open
In this work, we study the emergence of polarization doping in AlxGa1−xN layers with graded composition from a theoretical viewpoint. It is shown that bulk electric charge density emerges in the graded concentration region. The magnitude o…
View article: Macrosteps dynamics and the growth of crystals and epitaxial layers
Macrosteps dynamics and the growth of crystals and epitaxial layers Open
Step pattern stability of the vicinal surfaces during growth was analyzed using various surface kinetic models. It was shown that standard analysis of the vicinal surfaces provides no indication on the possible step coalescence and therefo…
View article: On network suppression of multidrug-resistant pathogen spread
On network suppression of multidrug-resistant pathogen spread Open
In the paper we present a system of SIS type equations coupled by impulses at fixed times that describe the transfer of patients in the healthcare system represented by a graph of healthcare facilities and corresponding communities. The fi…
View article: Critical Evaluation of Various Spontaneous Polarization Models and Induced Electric Fields in III-Nitride Multi-Quantum Wells
Critical Evaluation of Various Spontaneous Polarization Models and Induced Electric Fields in III-Nitride Multi-Quantum Wells Open
In this paper, ab initio calculations are used to determine polarization difference in zinc blende (ZB), hexagonal (H) and wurtzite (WZ) AlN-GaN and GaN-InN superlattices. It is shown that a polarization difference exists between WZ nitrid…
View article: Effects of incomplete inter-hospital network data on the assessment of transmission dynamics of hospital-acquired infections
Effects of incomplete inter-hospital network data on the assessment of transmission dynamics of hospital-acquired infections Open
In the year 2020, there were 105 different statutory insurance companies in Germany with heterogeneous regional coverage. Obtaining data from all insurance companies is challenging, so that it is likely that projects will have to rely on d…
View article: Relevance of intra-hospital patient movements for the spread of healthcare-associated infections within hospitals - a mathematical modeling study
Relevance of intra-hospital patient movements for the spread of healthcare-associated infections within hospitals - a mathematical modeling study Open
The aim of this study is to analyze patient movement patterns between hospital departments to derive the underlying intra-hospital movement network, and to assess if movement patterns differ between patients at high or low risk of coloniza…
View article: Modelling pathogen spread in a healthcare network: Indirect patient movements
Modelling pathogen spread in a healthcare network: Indirect patient movements Open
Inter-hospital patient transfers (direct transfers) between healthcare facilities have been shown to contribute to the spread of pathogens in a healthcare network. However, the impact of indirect transfers (patients re-admitted from the co…
View article: Impact of inter-hospital transfers on the prevalence of resistant pathogens in a hospital–community system
Impact of inter-hospital transfers on the prevalence of resistant pathogens in a hospital–community system Open
The spread of resistant bacteria in hospitals is an increasing problem worldwide. Transfers of patients, who may be colonized with resistant bacteria, are considered to be an important driver of promoting resistance. Even though transmissi…
View article: Phase-amplitude functional theory -- new ab initio calculation method\n for large size systems
Phase-amplitude functional theory -- new ab initio calculation method\n for large size systems Open
New method for ab initio calculations of the properties of large size system\nbased on phase-amplitude functional is presented. It is shown that Schrodinger\nequation for many electrons complex system including large size molecules, or\ncl…
View article: Analysis of the hospital records from AOK Plus
Analysis of the hospital records from AOK Plus Open
We present analysis of anonymised admission/discharge data from insurance provider for Saxony and Thuringia (Germany) for years 2010--2016. Study of such data are necessary to derive a structure of healthcare system transfer network, as no…
View article: Analysis of the AOK Lower Saxony hospitalisation records data (years 2008 -- 2015)
Analysis of the AOK Lower Saxony hospitalisation records data (years 2008 -- 2015) Open
Multidrug-resistant Enterobacteriaceae (MDR-E) have become a major public health threat in many European countries. While traditional infection control strategies primarily target the containment of intra-hospital transmission, there is gr…
View article: Impedance Development after Hybrid-L Implantation
Impedance Development after Hybrid-L Implantation Open
Nowadays, more and more patients with residual hearing especially in the low frequency range receive a cochlear implant (CI). In order to protect the residual hearing, shorter and thinner electrode arrays were developed that enable atrauma…