The main trends in the development of technology for nitride heterostructures element base of microwave−technology and power electronics, as well as light−emitting diodes have been reviewed. It has been noted that most modern technological focus is the development of nitride heterostructures on silicon substrates. The basic problems of nitride compounds on silicon substrate and the ways of their solution have been discussed. 

Some results of GaN/Si heterostructures technology development in «Elma−Malachit» JSC have been presented. The AlGaN/GaN/Si heterostructures have been grown by MOCVD. We show that early process stages such as Si−surface treatment and Al pre−deposition are of great importance for the growth of crack−free structures with good structural and surface quality. Meanwhile the surface curvature of the grown structures is influenced mainly by the composition of multilayered transition region between the AlN nucleation layer and the GaN layer. Transistors fabricated on AlGaN/GaN structures grown on Si substrates under optimized conditions demonstrated rather good static characteristics: Id,max = 800 mA/mm, Ubr > 120 V, gm = = 170 mS/mm. 

For the further technology development experimental and technological work should be arranged in close coordination with analytical prediction and calculation of properties of the grown material with mathematical modeling methods. This approach will help enhance the efficiency of technology development and deepen scientific views on the processes responsible for the formation of properties of heterostructures. 

In this paper, we have studied the limitcapabilities of nitride and arsenide HEMTs and shown that the frequency limit of these devices has already been reached. The nature of these frequency constraints arise from device design rather than from semiconduc- tor properties. In particular we have established that the product tBCdg is the critical parameter which could not be minimized any further technologically. In summary it could be stated that nowadays InP pHEMTs offer the highest frequencies and GaN HEMTs on SiC substrate are the most powerful devices. In addition we have shown that the breakdown voltages and power density of nitride HEMTs at a given operating frequency are controlled by heterostructure barrier layer thickness, increasing with decrease of the latter. Therefore it is necessary to develop high efficiency nitride nanoheterostructures with tB less than 10 nm. In this respect the AlN/GaN heterostructures are beyond comparison due to the good performance of 2D gas and relative simplicity of growth process. 

Point defects play a key role in many of the microelectronics device technologies. Knowledge of the properties of point defects and characteristics of their behavior during radiative synthesis of microstructures for use in silicon devices allows one to optimize the 

conditions of their production, improve their quality and improve the electronic properties. To a large extent this was due to the complexity of measuring the parameters of point defects. In this situation, of valuable help in studying the properties of point defects is numerical modeling, especially with the use of quantum mechanical methods based on density functional theory approach. 

The paper describes a systematic study of the effect of various quantum−mechanical simulation approximations influence the calculated energy parameters of defects as applied to simple point defects in silicon. We have demonstrated that the choice of the form of the exchange−correlation functional has the strongest effect on the predicted defect formation energy, whereas the variation of the other considered approximations is of secondary importance for simulation predictions. 

The advanced development of computer technology and software makes possible remote simulation of physical processes in technological processes using complex software systems. Its advantage is that the users (Clients) carry out the main creative work (the preparation and treatment of the calculated data) on their own computers, but the long−time calculations are executed by means of Internet access on a remote supercomputer (Server) where the software package is installed. The presented examples illustrate an application of CrystmoNet code to a number of tasks related to the conjugated simulation of Czochralski silicon single crystal growth. They include results of conjugated calculations of the hydrodynamic processes occurring in the melt taking into account its crystallization and the radiation−conductive heat transfer in the entire volume of the crystal growth hot zone, as well as the thermal stresses and the distributions of intrinsic point defects in dislocation−free silicon single crystals. 

A very important task on the way of improving the technologies of synthesizing highly effective light−emitting diodes on the basis of silicon is theoretical research into the formation of point defect clusters. One method of obtaining silicon with photoluminescent properties is radiation impact. It causes the formation of various defects in its structure, including point and linear defects, their clusters and complexes. In this paper a mathematical model was used to determine the coordinates and velocities of all particles in the system. The model was used for describing of point defect formation processes and studying their evolution with time and temperature. The multi−parametrical Tersoff potential was used for the description of interactions between particles. The values of the Tersoff potential were selected by solving the parametrical identification problem for silicon. For developing the models we used the system cohesive energy values obtained by an ad initio calculation based on the density functional theory (DFT). The resultant computer model allows MD simulation of silicon crystal structure with point defects and their cluster with possible visualization and animation of simulation results. 

Theoretical analysis of optimization options for the properties of CdTe absorber layer is an important task for increasing the efficiency of CdTe/CdS heterojunction based thin−film solar cells. Properties of the materials (e.g. the density of free carriers) often depend essentially on the parameters of the deposition process and subsequent treatment which determine the defect composition of the material. In this work a model based on the lattice kinetic Monte−Carlo method is developed to describe the process of CdTe deposition as a function of temperature and Cd and Te fluxes. To determine the effect of the treatment conditions on CdTe conductivity, we developed a quasichemical model based on the electrical neutrality equation for point defects concentrations that are described by defects formation reaction constants. Parameter obtained from the first−principles density functional calculations were used when developing the models. The developed deposition model correctly describes the transition from evaporation to precipitation as well as the increased evaporation rates in excess of Cd. To explain the observed electrical properties of CdTe after Cl−treatment, we complemented the quasichemical defect model by a deep acceptor complex defect that allowed us to describe both the high−temperature dependence of conductivity on the Cd pressure and the dependence of resistivity on Cl concentration at room temperature. 

Study of the electronic and structural properties of AlN thin films is an important problem because these films are widely used as buffer layers for GaN−based semiconductor heterostructures growth on Si substrates. In this paper we performed a theoretical investigation of the properties of Al−terminated AlN(0001) surface in the framework of density functional theory. Ab initio calculations allowed us to study the impact of in−plane lattice strain on the surface energy of this surface. We show that the presence of the compressive strain leads to a decrease of the AlN(0001) surface energy while tensile strain increases the surface energy of this surface. Surface energy values allowed us to calculate the stress value of the surface under investigation. Also we calculated the curvature of the AlN surface as a function of film thickness for free growth. The resultant curvature values are in a good agreement with known experimental results. 

This paper describes the problem of increasing the reliability of electronic components (EC) used for the fabrication of high−tech products. Two main ways of solving the problem are considered based on analysis of published data. One approach is Rejection of EC at the input control using special testing methods combined with burn−in test program. This testing reveals components with «hidden defects», counterfeit parts and components with incompatible construction materials both internal and with external service conditions. The other approach considers the feature of creating EC with nanoscale parameters. In this case the modular principle is applied for the design of devices that allows significantly reducing the loads on single elements, and malfunction of a discrete module causes its disconnection from the scheme followed by reconfiguration of the EC structure. We show that in general the problem of increasing reliability is a complex task related to developing an optimum structure of IC elements, informed choice of materials, testing and optimization of circuit solutions. 

This work is an analysis of the possible role of deep acceptor centers in silicon in the formation of the experimentally observed thermal acceptor effect consisting in the change from n to p conductivity type after annealing of electron or neutron irradiated high resistivity silicon. Based on the solution of the electrical negativity equation for compensated silicon we have estimated the dependence of the concentration of deep acceptor centers that is required for changing to p−type conductivity on acceptor energy level and shallow donor concentration.
We show that deep acceptor centers can make a significant contribution to the thermal acceptor effect in high resistivity silicon (energy levels of up to 0.4 eV). The concentrations of deep acceptor centers required for changing the conductivity type are of the order of 1012— 1014 cm−3. These concentrations seem to be achievable in samples containing low shallow donor concentrations (1012—1013 cm−3). Such centers can be divacancy−impurity complexes (Fe, P) with ionization energies of up to 0.34 eV. The thermal activation of interstitial boron is not excluded either. 

In this paper, we used the method of conversion electron Mössbauer spectroscopy to study the magnetic and electric hyperfine interactions in the surface layers of epitaxial films of yttrium iron garnet (111) grown by liquid phase epitaxy. We observed a violation of the stoichiometry in the surface layers of the anion sublattice (≈ 8 ⋅ 10−8 m) of the yttrium iron garnet epitaxial film and, as a consequence, the formation of two types of d−positions, due to the large concentration of point defects in the anion sublattice in the surface area and increasing degree of covalence of the chemical communication in the film/air transition layer. We also revealed the existence of fixed doublet components which correspond to the iron ions in the paramagnetic state with an intermediate valence of +2 ... +3. Application of the Hamiltonian mixed quadrupole diagonalization method and magnetic interactions to interpret the spectrum opened up the possibility of constructing a vector diagram of the spatial orientation of the effective magnetic fields at the Fe57 nuclei, resulting in restoration of the resultant magnetic moment vector formation mechanism for the yttrium iron garnet epitaxial film. We recorded a slight noncollinearity of magnetic moments at the a− and d−positions of iron which is equal to ≈ 4°. The results complement the experimental data on the formation of coherent electric and magnetic hyperfine interactions in epitaxial ferrite−garnet films and must be taken into account in the practical use of the magnetic properties of these materials. 

Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions. The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth. The crystals were irradiated by protons with an energy of 6 MeV and doses of 5 · 1013, 1015 and 1 · 1017 p+/cm2 at 40 °C in a U−120 cyclotron. 

The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si1−xGex (x = 0,03) whiskers in the 4,2—300 K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4,2—40 K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1·1017 p+/cm2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field−caused decrease in the mobility of free charge carriers (holes). It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8 T. 

For the 70th anniversary of the birth of Anatolii Vasil'evich Dvurechenskii