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The electronic structures of substitutional rare-earth (RE) impurities in GaAs and cubic GaN are calculated. The total energy is evaluated with the self-interaction corrected local spin density approximation, by which several configurations…
This paper presents first principles calculations of paramagnetic cubic CrN$_x$ with the aim to provide deeper insight into recently published transmission electron microscopy-based study on this material. Among several types of point…
We have performed a first-principles study of the p- and n-type conductivity in CuIn$_{1-x}$Ga$_x$Se$_{2}$ due to native point defects, based on the HSE06 hybrid functional. Band alignment shows that the band gap becomes larger with $x$ due…
A two-band model with repulsive interband coupling and interband {\it transport} (potential) scattering is considered to elucidate their effects on material properties. In agreement with previous work, we find that the bands order…
The nature of the lattice instability connected to the structural transition and superconductivity of (Sr,Ca)$_3$Ir$_4$Sn$_{13}$ is not yet fully understood. In this work density functional theory (DFT) calculations of the phonon…
The discovery that the interface between two band gap insulators LaAlO3 and SrTiO3 is highly conducting has raised an enormous interest in the field of oxide electronics. The LAlO3/SrTiO3 interface can be tuned using an electric field and…
Holding promising applications in power electronics, the wide band gap material gallium oxide has emerged as a vital alternative to materials like GaN and SiC. The detailed study of phonon modes in $\beta$-Ga$_{2}$O$_{3}$ provides insights…
We have performed accurate \emph{ab--initio} pseudopotential calculations for the structural and electronic properties of ZnSe/GaAs(001) heterostructures with interface configurations accounting for charge neutrality prescriptions. Beside…
Semiconductors with wide band gap (3.0 eV), high dielectric constant (> 10), good thermal dissipation, and capable of $n$- and $p$-type doping are highly desirable for high-energy power electronic devices. Recent studies indicate that $\rm…
The semiconducting behaviour and optoelectronic response of gallium nitride is governed by point defect processes, which, despite many years of research, remain poorly understood. The key difficulty in the description of the dominant…
Erbium (Er) doped GaN has been studied extensively for optoelectronic applications, yet its defect physics is still not well understood. In this work, we report a first-principles hybrid density functional study of the structure,…
We investigate the structural, electronic, vibrational, power and transport properties of the $\beta$ allotrope of Ga$_2$O$_3$ from first-principles. We find phonon frequencies and elastic constants that reproduce the correct band ordering,…
Point defects may introduce defect levels into the fundamental band gap of the host semiconductors that alter the electrical properties of the material. As a consequence, the in-gap defect levels and states automatically lower the threshold…
Using hybrid density functional theory, we address point defects susceptible to cause charge compensation upon Mg doping of GaN. We determine the free energy of formation of the nitrogen vacancy and of several Mg-related defects. The…
Distortions of the $\sqrt3\times\sqrt3$ Sn/Ge(111) and Sn/Si(111) surfaces are shown to reflect a disproportionation of an integer pseudocharge, $Q$, related to the surface band occupancy. A novel understanding of the $(3\times3)$-1U (``1…
In the present Ph.D. Thesis we report an experimental investigation on the effects of gamma- and beta-ray irradiation and of subsequent thermal treatment on many types of a-SiO2 materials, differing in the production methods, OH- and…
In this study, we employ a first-principles approach to conduct a comprehensive investigation of the properties of nine common native point defects in cubic boron nitride. This analysis combines standard semi-local and dielectric hybrid…
We have performed density functional theory (DFT) calculations to characterize the energetics, and the atomic and electronic structure, of stacking faults in GaN, both in the stable hexagonal wurtzite (wz) phase and in the metastable cubic…
Monoclinic $\beta$-Ga$_2$O$_3$, a promising wide band gap semiconducting material, exhibits complex, anisotropic diffusional characteristics and mass transport behavior as a results of its low symmetry crystal structure. From…
Results of our shell-model calculations concerning the determination of empirical parameters of inter-ionic potentials and the formation energies of point defects in LiNbO3 are presented. We employed the relaxed fitting method which is…