V. N. Petrov

Effect of growth kinetics on the InAsGaAs quantum dot arrays formation on vicinal surfaces

Using scanning tunneling microscopy we have studied the influence of initial stage (up to 1.5 monolayers) growth kinetics on the surface morphology of 3 ML InAs/GaAs(100) grown on vicinal surfaces (misoriented by 3° and 7° towards [011] direction) by different modifications of molecular beam epitaxy. The results presented clearly show the influence of growth kinetics on the arrangement of InAs/GaAs quantum dot arrays on vicinal surfaces.

STM and RHEED study of InAsGaAs quantum dots obtained by submonolayer epitaxial techniques

Formation of uniform arrays of InAs quantum dots on GaAs(100) singular and vicinal (3° towards [011] direction) surfaces crucially depends on the deposition mode chosen. For dots formed with continuous As flux impinging on the surface and simultaneous submonolayer In deposition cycles, intentional substrate misorientation significantly decreases the density of dots and stimulates their ordering along the [001] direction. On the contrary, growth using alternate In and As deposition cycles results in a reduced density of dots for singular surfaces and in strongly increased dot concentration for vicinal ones. Ordering of dots in chains along [001] and [010] directions is observed for the alternative deposition on singular substrates.

Fabrication of InAs quantum dots on silicon

Reflection high-energy electron diffraction and scanning tunneling microscopy have been used to demonstrate for the first time that InAs quantum dots may be fabricated directly on Si(100) by molecular beam epitaxy. It is shown that heteroepitaxial growth in an InAs/Si system takes place by the Stranski-Krastanow mechanism and the surface morphology depends strongly on the substrate temperature.

The emission from the structures with arrays of coupled quantum dots grown by the submonolayer epitaxy in the spectral range of 1.3–1.4 µm

Optical properties of structures with vertically coupled quantum dots grown by the combined submonolayer molecular-beam epitaxy were investigated. It is shown that the formation of the laterally coupled conglomerates of quantum dots are possible in upper rows for certain parameters of growth, with the corresponding photoluminescence emission being in the wavelength range of 1.3–1.4 µm at room temperature.

Heteroepitaxial growth of InAs on Si: A new type of quantum dot

The mechanism for heteroepitaxial growth in the InAs/Si system is studied by reflection highenergy electron diffraction, scanning tunnelling microscopy, and photoluminescence. For certain growth conditions, InAs nanostructures are found to develop on the Si surface immediately during the growth process in the course of molecular beam epitaxy. The range of substrate temperatures that lead to formation of nanosized islands is determined. InAs quantum dots grown on a buffer Si layer with a silicon layer of thickness 50 nm grown on the top produced photoluminescence lines at a wavelength of 1.3 µm at 77K and 1.6 µm at 300 K.

Recombination emission from InAs quantum dots grown on vicinal GaAs surfaces

Photoluminescence (PL) spectra of InAs/GaAs heteroepitaxial structures with quantum dots (QDs) have been studied. The structures were grown by submonolayer migration-enhanced epitaxy on vicinal substrates with the amount of deposited InAs close to the critical value of 1.8 monolayer (ML). The origin and evolution of the structure of PL spectra were studied in relation to the direction and angle of misorientation, temperature, and power density and spectrum of the exciting radiation. A blue shift and narrowing of the PL band with increasing misorientation angle was established experimentally. The fact that QDs become smaller and more uniform in size is explained in terms of a lateral confinement of QDs on terraces with account taken of the step bunching effect. The temperature dependences of the positions and full widths at half-maximum (FWHM) of PL bands are fundamentally different for isolated and associated QDs. The exciton ground states contribute to all low-temperature spectral components. The excited exciton state contributes to the recombination emission from QDs, as evidenced by the temperature dependence of the integrated intensity of the PL bands. A quantitative estimate is given of the electronic structure of different families of InAs QDs grown on GaAs substrates misoriented by 7° in the [001] direction.

Effect of self-organization, defects, impurities, and autocatalytic processes on the parameters of ZnO films and nanorods

The effects of the parameters of ZnO-film deposition onto different substrates using the method of ac magnetron sputtering in a gas mixture of argon and oxygen hare studied. The phenomenon of self-organization is observed, which leads to invariability of the surface morphology of the ZnO films upon a variation in the substrate materials and deposition parameters. The parameters of the macro- and micro-photoluminescence spectra of the films differ insignificantly from the parameters of the photoluminescence spectra of bulk ZnO crystals obtained by the method of hydrothermal growth. The presence of intense emission with a narrow full-width at half-maximum (FWHM) in different regions of the spectrum allows ZnO films obtained by magnetron sputtering doped with rare-earth metal impurities (REIs) to be considered as a promising material for the creation of optoelectronic devices working in a broad spectral range. The possibility of the implementation of magnetic ordering upon legierung with REIs significantly broadens the functional possibilities of ZnO films. The parameters of the photoluminescence spectra of ZnO nanorods are determined by their geometrical parameters and by the concentration and type of the impurities introduced.

Low-temperature transport properties of multigraphene films grown on the SiC surface by sublimation

Multigraphene films grown by sublimation on the surface of a semi-insulating 6H-SiC substrate have been studied. It is shown that pregrowth annealing of the substrate in a quasiclosed growth cell improves the structural quality of a multigraphene film. Ohmic contacts to the film have been fabricated, and the Hall effect has been studied at low temperatures. It is found that a 2D electron gas exists in the films. It is concluded that the conductivity of the film is determined by defects existing within the graphene layer or at the interface between the graphene film and a SiC substrate.

1.3-1.4 µm photoluminescence emission from InAs/GaAs quantum dot multilayer structures grown on GaAs singular and vicinal substrates

Optical and structural properties of multilayer structures with InAs/GaAs quantum dots are investigated. It is shown that under optimal growth conditions, 1.3-1.4 µm emission can be achieved. Possible scenarios of quantum dot behaviour evaluation are discussed in a frame of elastic theory to explain differences in optical properties of the grown structures.

System for recording and analysis of reflection high-energy electron diffraction patterns

An efficient and fast system for recording and analysis of reflection high-energy electron diffraction (RHEED) patterns is described. The software developed for this system includes three program packages: one for operating in the single-window mode, one for operating in the four-window mode, and one for the linear regime. Examples are given of the use of the system for monitoring and control of growth of III–V semiconductor compounds by molecular-beam epitaxy. Using this system, we discovered an effect wherein a periodic splitting of the RHEED peaks occurs during the growth of GaAs (100).