A. P. Kokhanenko

Heterostructures with self-organized quantum dots of Ge on Si for optoelectronic devices

In this paper an analysis of tendencies of Ge on Si quantum dots nanoheterostructures’ usage in different optoelectronic devices such as, for example, solar cells and photodetectors of visible and infra-red regions is carried out; a complex mathematical model for calculation of dependency on growth conditions of self-organized quantum dots of Ge on Si grown using the method of molecular beam epitaxy parameters is described. Ways of segregation effect and underlying layers’ influence are considered. It is shown that for realization of good device characteristics quantum dots should have high density, small sizes, uniformity, and narrow size distribution function. The desirable parameters of arrays of square and rectangular quantum dots for device application are attainable under certain growth conditions.

Critical thickness of 2D to 3D transition in GexSi1−x/Si(001) system

In this paper, Stranski–Krastanov growth of GexSi1−x epitaxial layers on the Si(001) surface is considered. Experimental investigations show that the moment of transition from 2D to 3D growth and the critical thickness of 2D layer at which this transition occurs play a key role during the synthesis of such materials. Among the most important parameters determining the peculiarities of the growth process and characteristics of emerging island ensembles are growth temperature and surface conditions (for example, the presence of surfactants). But existing theoretical models are not able to predict the values of the critical thickness in the whole range of growth temperatures and compositions x of solution for these systems. For the calculations of the critical thickness of transition from 2D to 3D growth, in this paper, a theoretical model based on general nucleation theory is proposed. This model is specified by taking into account dependencies of elastic modulus, lattices mismatch, and surface energy of th...

High temperature electron irradiation and isochronal annealing of p-Hg1−x Cd x Te crystals

Abstract The peculiarities of defect formation in p-Hgi-x Cd x Te crystals (x=0.195−0.205) at electron irradiation (2.3 MeV, 300 K) up to 1 × 1018 cm−2 were investigated. It was shown that the charge carrier lifetime changed with the irradiation due to variation of the free charge carrier density and the recombination-type centre concentration. A distance of recombination centres from the valence band of 35–55 meV for the electron irradiated crystals is determined. The isochronal annealing temperature ranges for the recombination-type radiation defects and electrically active defects, induced by the irradiation, are found.

Energy-band diagrams and capacity-voltage characteristics of CdxHg1−xTe-based variband structures calculated with taking into account dependence of electron affinity on a composition

The purpose of this scientific work is the research of energy-band diagrams and capacity-voltage characteristics of CdxHg1−xTe-based variband heteroepitaxial structures with taking into account the dependence of electron affinity on the composition.Numerical simulations of energy-band diagrams and capacity-voltage characteristics for metal-insulator-semiconductor structures based on CdxHg1−xTe-variable composition layers are carried out in this work. Energy diagrams are calculated with taking into account the dependence of electron affinity on the composition x of CdxHg1−xTe. This dependence was obtained in terms of dependence of the local electroneutrality level on the composition for CdxHg1−xTe.

Photoelectric Properties of Photodetectors Based on Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

We have calculated the spectral, threshold, and noise characteristics of p-Si–PtSi photodetectors with highly-doped surface layers produced by molecular-beam epitaxy and short-pulse ion implantation by a recoil method.

Charge-carrier lifetime in Hg1−xCdxTe (x=0.22) structures grown by molecular-beam epitaxy

Measurements of the charge carrier lifetime in epitaxial structures based on narrow-gap Hg1−xCdxTe (x=0.22), grown by molecular-beam epitaxy with pulsed excitation using radiation at different wavelengths, are reported. It is shown that in p-type epitaxial films the lifetime is determined by the Auger recombination mechanism at temperatures corresponding to the impurity conductivity, and for n-type epitaxial films recombination via local centers is characteristic.

Elongated Quantum Dots of Ge on Si Growth Kinetics Modeling with Respect to the Additional Energy of Edges

In this paper refining of mathematical model for calculation of parameters of selforganised quantum dots (QDs) of Ge on Si grown by the method of molecular beam epitaxy (MBE) is done. Calculations of pyramidal and wedge-like clusters formation energy were conducted with respect to contributions of surface energy, additional edge energy, elastic strain relaxation, and decrease in the atoms attraction to substrate. With the help of well-known model based on the generalization of classical nucleation theory it was shown that elongated islands emerge later than pyramidal clusters. Calculations of QDs surface density and size distribution function for wedge-like clusters with different length to width ratio were performed. The absence of special geometry of islands for which surface density and average size of islands reach points of extremum that was predicted earlier by the model not taking into account energy of edges was revealed when considering the additional contribution of edge formation energy.

Photodetectors and solar cells with Ge/Si quantum dots parameters dependence on growth conditions

In this paper recommendations for growth conditions necessary for achieving maximum detectivity of infrared photodetectors with quantum dots and efficiency of quantum dot solar cells are given. It is also shown that for improvement of photodetectors characteristics quantum dots should be grown at rather high temperatures, and, on the contrary, at relatively low temperatures for maximisation of solar cells efficiency.

Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

The spectral characteristic of infrared silicon–platinum silicide Schottky barrier photodetectors is shifted to the long wavelength region due to a highly-doped surface silicon layer produced by recoil boron implantation. The dependence of the resulting highly-doped layer parameters on high-energy boron-ion implantation regimes is studied experimentally. Energy-band diagrams and reduction of the barrier height are calculated for p-Si–PtSi structures with highly-doped surface layers produced by molecular-beam epitaxy and recoil implantation.

Recombination of nonequilibrium charge carriers in epitaxial Hg1−x Cdx Te MBE films

We present the results of charge-carrier lifetime measurements in narrow-band Hg1−xCdxTe epitaxial structures (x=0.210–0.225) grown by molecular-beam epitaxy (MBE) using pulsed excitation by radiation at various wavelengths. In p-type epitaxial films the carrier lifetime is governed by Shockley-Read recombination at impurity-conduction temperatures. The governing factor for n-type epitaxial films is Auger recombination, with some contribution from other recombination mechanisms (surface and macrodefects).