The dependence of the energy change in the adsorption process on the position of the Fermi level and the associated possibility of electron transfer between the adsorbate and the semiconductor was discovered. The effect induces a step change in the adsorption energy at the critical surface coverage at which the Fermi level becomes free. This occurs in the absence of band bending at the surface. At this coverage, the equilibrium pressure of the adsorbate in the gas phase generally may change by many orders of magnitude, thus the growth of the semiconductor layers/crystals occurs at the critical coverage.

Attachment of the adsorbate occurs at the minimum potential near the surface, which induces accelerating it on its way to the minimum and acquiring considerable kinetic energy. Its dispersion occurs during a very short time of its collision with the surface. The proposed model for the dissipation of the kinetic energy (i.e. of the momentum component perpendicular to the surface) assumes tunneling of the electron into the interior enforced by a strong Lang-Kohn field attracting the electron into the interior of the crystal and ionizing the adsorbate. The positively charged adsorbate is strongly repelled, causing loss of its momentum and smooth attachment to the surface.

In the crystallization process, the atoms are localized in the lattice sites, resulting in zero configuration entropy from the arrangement of atoms at the lattice sites. Their removal will empty the nodes, allowing also occupation of the states outside the nodes. A dual state (in a node and outside a node) can only be occupied by a single atom. The calculation of the configurational entropy in this model determined the entropy change during the transformation from the gas phase to the crystalline phase, the result which is consistent with the thermodynamic data.

Spontaneous polarization induces electric field that is not screened in the case of quantum wells buried inside semiconductors. In contrast, the effect of polar surfaces is screened. Therefore, there are no fields in the wells in the zinc-blende but such there are in the case of wurtzite. A local model has been constructed that allows, according to Landau's definition, to calculate spontaneous polarizations independent of external surfaces, i.e., in an unique way, such procedure has been contested so far.

In nitride semiconductors, hybridization sp3 of the nitrogen states during bonding does not occur - two separate valence subbands of s and p states are formed. However, the tetrahedral structure of the lattice remains. This occurs due to the existence of nitrogen resonance states with fractional occupancies, which allows tetrahedral coordination of the nitrides wurtzite lattice.

The capture of majority carriers can lead to the formation of charged states of the deep defects. Minority carriers can thus be accelerated in the electric field of the charged defects. The field can be shielded which causes the recombination dependence on the density of the carriers. As a result, non-radiative SRH recombination does not disappear in the vicinity of the absolute zero temperature.

In inhomogeneous nitride layers, a non-zero electric charge emerges, due to the polarization doping effect identified by D. Jena. Such effect does indeed occur, which we proved using a constructed atomic model for ab initio calculations and determination of the spatially slowly varying component of the electric potential. This charge is immobile, associated with lattice bonds, not leading to the electrical conduction. A scenario was formulated for the appearance and compensation of two types of the charge in parallel: bonding and mobile, followed by a new scenario for the appearance of mobile charge which leads to temperature-independent electrical conductivity of the p-GaN type. The obtained scenario of the appearance of electrical conductivity leads to overcome of low p-type conductivity of nitride semiconductors, the key barrier in the development of LED and LD devices.

The set of parallel steps during step-flow growth is stabilized by their diffusional repulsion. However, the observed growth is unstable, macro-steps appear. Accordingly, a new mechanism for the appearance of two and larger height steps, i.e. macrosteps, has been proposed. They emerge due to the instability of a sequence of step, i.e. step train which is a finite set of dense steps surrounded by more separate steps. In this instability, the last step of the train is faster and captures the previous one to form a double step. As a result, the double step is slower so the next steps join. According to this scenario, a macro-degree is formed by capture of the steps from the following step train.

The time dependence of photoluminescence decay has been converted into a dependence on the flux of the emitted light. This results in the conversion of the ABC coefficients of recombination into set of coefficients of polynomial powers of the light intensity. Determination of the coefficients requires noise removal. A noise averaging model has been proposed, which determines the contribution of different types of recombination (SRH, optical, Auger). Thus, it is possible to characterize the optical properties of semiconductor systems by using direct measurement of radiative recombination.

Simulations of GaN crystal melting by ab initio molecular dynamics led to a new picture of GaN crystal decomposition at high temperatures. The characterization of the transformation was carried out using several methods: layer averaging, density correlation functions, covalent bond analysis and temporal change of interatomic distances. The results determined decay of the far distance order of the lattice. In the case of close distance order, the two types of decay were distinguished: to the atomic and the molecular states. Decay to the atomic state, or melting, occurs only at high pressures, above 12 GPa. At lower pressures, decay leads mainly to the molecular state, i.e. to N₂ molecules, which effectively leads to the separation of the gas and liquid phases, i.e. to the separation of gas and the formation of a nitrogen solution in the liquid metal.

Schottky barrier formation was proven for the contact between any metal and p-type GaN. An image of the Au-GaN system in ab initio studies was obtained. The electrical state of the Au-GaN p-type contact was obtained. It was also shown that heavy Mg doping the lowers the hole energy barrier, while moderate compensation is neutral. The mechanism of low resistance contact formation by annealing the Ni/Au contact in an oxidizing environment was elucidated. A new type of contact formed by layered implantation with a multilayer implantation of deep acceptors was proposed.

The time evolution of diffusion-controlled growth results form the dual nature of the diffusion: averaged classical field and stochastic motion of atoms. In general, both effects lead to the instability of the growth, moreover, they can be coupled. The opposing stabilizing effects are: surface energy i.e. surface tension, and the surface diffusion. In the case of diffusion of a large mean free path, i.e., ballistic, growth is destabilized uniformly by chaotic attachment of atoms, and stabilized by surface diffusion. A kinetic condition was derived that determines the relative contribution of these two factors, leading to a number of different types of growth, which were classified. In the case of a short mean free path, growth destabilizes through the corner effect. It was shown that the transition between ballistic and diffusive growth occurs for the crystal size equal to four mean free path lengths. It was shown that in the case of growth strongly dominated by volumetric diffusion (high supersaturation), fractal growth occurs, and in the case of dominance of surface diffusion, crystal growth dominates that can be destabilized by formation of the side branches or dendrites. It was shown that the formation of side branches depends also on surface diffusion which adds to the effect of surface tension identified by other authors. In the case of 2-d shapes, the formation of capillary waves was observed, which destabilizes the shapes. A similar meandering effect was modeled and observed for the formation of steps on the GaN surface in MOVPE growth.

Ab initio methods use quantum wells geometry, which allows simulations of real well structures within a certain range of thicknesses, due to their translational invariance. This allowed identification and accurate determination of the electric fields in the wells, their effects on recombination processes, including the relationship of recombination energy and efficiency to well geometry and barriers. These results served to determine the magnitude of the Quantum Confined Stark Effect (QCSE) in the wells, related to the influence of the spontaneous and piezo polarization.

Molecular nitrogen is a strongly bound system, which is called a molecular noble gas. The interaction of N₂ molecules is strongly anisotropic and weak, representing a correction 5 orders of magnitude smaller than the total energy of the molecules. The anisotropic interaction potential as a function of 4 variables was therefore determined by ab initio high accuracy calculations. Applying this potential, a symplectic method of integrating of the equations of molecular dynamics of rigid rotors was used to obtain the equation of state and the viscosity of nitrogen at high pressures. In the case of viscosity, a new algorithm for momentum coupling, i.e. the momentum transfer to the rotational degrees of freedom of N₂ molecules at the solid-gas surface, was formulated .

Aluminum nitride has polar surface, terminated by Al atoms, so it should exhibit metallic properties, i.e. strongly catalyze the dissociation of N₂ molecules. The results of ab initio calculations indicate decrease of the N₂ dissociation barrier from 9.8 eV to 5.0 eV. In the presence of hydrogen, this should lead to the synthesis of ammonia. The calculations indicate that AlN can be used to catalyze ammonia synthesis. In addition, in the case of a mixture of nitrogen and oxygen, this can lead to the synthesis of NO, i.e. to obtain the synthesis of oxygen and nitrogen compounds, of enormous importance for the technology.

Molecular nitrogen has the highest binding energy of all diatomic molecules, equal to 9.8 eV. The dissociation of molecular nitrogen, necessary for the synthesis of nitrides, requires a strong catalytic effect. In ab initio calculations in the cluster model of liquid metal surfaces, it was shown that the liquid metals strongly catalyze the decomposition of the N2 molecule. Only the Li surface does not catalyze the dissociation due to the weak binding of lithium and nitrogen atoms.

In MOVPE nitride growth processes, a mixed NH2/NH3 coverage is formed on the GaN(0001) surface. The attachment of ammonia results in an excess of electrons in the system, while the electrons in NH2 radicals are missing. This results in charge balance for an NH2/NH3 ratio of 3:1 and the the Fermi level non-pinned. The application of a trace percentage of hydrogen in the gas phase causes an increase in the ratio of ammonia, and a strong reduction of the binding energy of In atoms. As a result, the lack of electron contribution causes blockade of indium adsorption on the GaN(0001) surface and virtually in complete blockade of its incorporation during MOVPE epitaxy of GaInN layers, as observed experimentally.

A number of results have been obtained for electronic and optoelectronic circuits based on wurtzite group III metal nitrides. The results were successfully applied to the design of nitride LD and LEDs

Ab initio calculations were performed for the oxygen adsorption on the tungsten surface W(110). A model of the adsorption site was constructed, containing two positions of the oxygen atom in the configuration of its three nearest neighbors - tungsten atoms. The obtained site model was confirmed by experimental studies. Subsequently, the ab initio results were used for Monte Carlo modeling of domain walls in O/W(110) adsorption.

The optical properties of GaN/AlGaN, GaN/AlN and InGaN/GaN nitride multi-quantum well systems were investigated. Theoretical results were used to verify several observed effects in PL, including shifts in emission energy, its intensity and decay time for different polar and non-polar wells.

Graphene - a few-layer analog of graphite - a 2-d variety of carbon can be formed on the surface of SiC by sublimation of silicon. Using ab initio calculations, the atomic mechanism of growth on the carbon SiC surface was determined, related to the absence of strong bonding between the graphene layers and SiC surface, which creates the possibility of escape of silicon atoms through an open channel created by large distance between graphene and the SiC surface. This allows dozens of graphene layers to grow on the carbon surface. In contrast, graphene is strongly bonded to the silicon SiC surface which prevents silicon from escaping because the graphene layers do not allow Si atoms to pass through. As a result, a few, no more than 3-4 graphene layers are formed on the silicon surface, mainly by the escape of Si through defects in the graphene structure. It has been also shown that annealing graphene layers on the silicon surface of SiC in hydrogen atmosphere results in its detachment by saturating silicon bonds with hydrogen.

Thermodynamic properties of Group III nitrogen-metal systems were determined, such as free energy, equilibrium pressure, solubilities of nitrogen in liquid metals, and others. These were determined by methods of fitting to thermodynamic properties, averaging and extrapolation of thermal properties, which supported the synthesis processes of nitrides: GAN, AlN and InN. Convection patterns in crystal growth systems, and models of the reaction of nitrogen-metals of Group III were developed.

The analytical solution of the nonlinear system of equations for the growth dynamics of the spherical growth of the new phase in the field of temperature and solution concentration was obtained. The result is exact for the specific initial conditions. In general, the system of growing excipient evolves to this solution asymptotically for long times for any initial condition.