თინათინ ლაფერაშვილი

The presented work emphases on the Solar Cells containing Quantum Dots (QDs) for next-generation photovoltaics. New technology of fabrication of InP nanostructured thin films, differing from the Stranski-Krastanov growth mode and from the formation of InP nanocrystals by droplet epitaxy is proposed. The technology includes electrochemical deposition and annealing in gas. The region of strong photosensitivity in the 1.75-2.05 eV area shown. The mechanism of the InP NCs formation on the GaP surface discussed taking into account obtained experimental data. 

The presented work emphases on the Solar Cells containing Quantum Dots (QDs) for next-generation photovoltaics. New technology of fabrication of InP nanostructured thin films, differing from the Stranski-Krastanov growth mode and from the formation of InP nanocrystals by droplet epitaxy is proposed. The technology includes electrochemical deposition and annealing in gas. The region of strong photosensitivity in the 1.75-2.05 eV area shown. The mechanism of the InP NCs formation on the GaP surface discussed taking into account obtained experimental data. 

Fabrication technology of InGaP nanocrystal layer on GaP surface is presented, which includes electrochemical deposition of thin films of InxGa1-x metallic alloys on a semiconductor and annealing in hydrogen. Undoped n-type GaP monocrystals grown by Czochralski method used in the experiment. The spectral characteristics of nanomaterial are studied. Infrared wavelength tuning of the InGaP/GaP system at room temperature achieved by means of changes in technological processes. The possibilities of application of InP/GaP/Si structure for Malty Junction Solar Cells are discussed.

We present the results of experimental studies of physical properties of the detection process of GaAs Schottky diodes for terahertz frequency radiation. The development of technology in the THz frequency band has a rapid progress recently. Considered as an extension of the microwave and millimeter wave bands, the THz frequency offers greater communication bandwidth than is available at microwave frequencies. The Schottky barrier contact has an important role in the operation of many GaAs devices. GaAs Schottky diodes have been the primary nonlinear device used in millimeter and sub millimeter wave detectors and receivers. GaAs Schottky diodes are especially interesting due to their high mobility transport characteristics, which allows for a large reduction of the resistance-capacitance (RC) time constant and thermal noise. In This work are investigated the electrical and photoelectric properties of GaAs Schottky diodes. Samples were obtained by deposition of different metals (Au, Ni, Pt, Pd, Fe, In, Ga, Al) on semiconductor. For fabrication metal-semiconductor (MS) structures is used original method of metal electrodepositing. In this method electrochemical etching of semiconductor surface occurs just before deposition of metal from the solution, which contains etching material and metal ions together. For that, semiconductor surface cleaning processes and metal deposition carries out in the same technological process. In the experiments as the electrolyte was used aqueous solution of chlorides. Metal deposition was carried out at room temperature.

The effect of annealing structures on the electrical and photoelectric properties of metal-semiconductor contacts was investigated. Metal/semiconductor structures have been fabricated by method of electrochemically deposition of In on the electrochemically cleaned surface of the semiconductors A3B5 (GaP, GaAs). The dark capacitance and current -voltage characteristics and the hotoelectric spectra of zero bias for front-illuminated contact show near-ideal Schottky barrier diode properties for annealing temperature up to 250-3000C. Was found that the spectra of zero bias photocurrent of In/GaP beside the region photoconductivity resulting from band to band excitation, contains, also, separated of them the region photoconductivity in a long wavelength of spectra, which is related to the interaction between the metal and semiconductor. Samples used for the fabrication of In/GaP diodes were growing by Chochralski method especially un doped n-type GaP into (III) oriented wafers. The thickness and carrier concentration was 200-250 mimic and (2-4). 10 exp17 atom/cm3 respectively. At first ohmical contact to the one side of wafer was formed by alloying of indium at the temperature 5000C for GaAs and 600°C for GaP during 5 min in hydrogen. Then the sample with ohmic contact and wire for preceding the power was coaled with chemical stable polystyrene solution except the area where the metal will be deposited. The wafers were then ached chemically, rinsed in distilled water and were transferred immediately into electrolyte for deposition of In.

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