Mohylyak I. Laser micro-nanostructuring and doping of near-surface layers of semiconductor materials.

The thesis studies the development of micro-nanostructuring of semiconductor materials and formation of ultrathin doped layers in semiconductors under the action of laser radiation. The possibility of micro-nanostructuring of monocrystalline silicon has been experimentally investigated using three types of lasers - ruby, neodymium and CO2 laser. It is shown that the melting of Si at threshold values of the energy of laser radiation has a local character and the shape of crystallized melts depends on the crystallographic orientation of the samples. Surface periodic structures with nanometer dimensions range are obtained. That can be used to create effective photovoltaic converters of solar energy. The possibility of solid-phase doping and formation in semiconductors of submicron doped layers under the action of powerful lasers pulses are experimentally examied. A p-n junction formed by means of laser stimulated diffusion of dopants into semiconductors (Si, GaAs, InP, InGaAsP, InGaAs) were investigated. SIMS and AES spectroscopy methods were used to measure the depth profiles of the incorporated impurities: B into Si, Zn into GaAs and InP. The volt-capacity method using an electrochemical profilometer was used for the charge carrier concentration distribution in the doped layer. Spectroscopy investigation have shown that during solid phase diffusion locally doped regions exactly reproduce the shape and size of the windows in the dielectrics. The concentration profiles of charge carrier distribution in the doped layers clearly show the specific processes of dopant diffusion and evaporation at laser solid-phase doping of semiconductors. The comparative analysis of parameters of formed semiconductor structure shows that the procedure of laser solid-phase doping can stand the comparison with technology of implantation and conventional diffusion technology. Since the laser solid-phase doping ensures also a high degree of reproducibility of p-n junction parameters, it can be effectively used for electronic devices fabrication.