B. M. Bulakh

The effect of oxidation on the efficiency and spectrum of photoluminescence of porous silicon

The photoluminescence spectra of porous silicon and their temperature dependences and transformations on aging are studied. It is shown that the infrared band prevailing in the spectra of as-prepared samples is due to exciton recombination in silicon crystallites. On aging, a well-pronounced additional band is observed at shorter wavelengths of the spectra. It is assumed that this band is due to the recombination of carriers that are excited in silicon crystallites and recombine via some centers located in oxide. It is shown that the broad band commonly observable in oxidized porous silicon is a superposition of the above two bands. The dependences of the peak positions and integrated intensities of the bands on time and temperature are studied. The data on the distribution of oxide centers with depth in the porous layer are obtained.

The electronic and emissive properties of Au-doped porous silicon

The temperature dependences of photovoltage induced by intense pulses of red and white light, along with the time-resolved spectral dependences of photoluminescence, are studied for porous silicon structures por-Si/p-Si). These structures have been obtained by anode etching of p-Si with subsequent Au doping from an aqueous solution with Au ion concentrations of 10−4 and 10−3 M. The current-voltage characteristics and electroluminescence of the resulting por-Si/p-Si and por-Si:Au/p-Si structures are also studied after a deposition of semitransparent Au electrodes on por-Si. It is shown that the Au doping changes the sign of the boundary potential of p-Si from positive to negative, alters the magnitude and sign of the photovoltage in the por-Si films, and eliminates photomemory phenomena, which are associated with the capture of nonequilibrium electrons at grain-boundary traps and por-Si traps. The formation of Au nanocrystals in por-Si substantially affects the current-voltage and photoluminescence characteristics. Electroluminescence is observed for the Au/por-Si:(Au, 10−3 M)/p-Si/Al structures and is attributed to emission from the nanocrystals.

Effect of adsorption and desorption processes on photoluminescence excitation spectra of porous silicon

Plenty photoluminescence (PL) and plenty photoluminescence excitation (PLE) spectra, as well as layer structure and surface substances on Si crystallites of porous silicon prepared by different technique, have been investigated by photoluminescence, atomic force microscope (AFM) and infrared (IR) transmission methods. It is shown that PLE spectra, consisted of several excitation bands, do not depend on Si crystallites sizes. The nature of excitation bands is discussed.

The interrelation of surface relief of porous silicon with specific features of Raman spectra

Structural characteristics and Raman spectra of porous silicon layers were investigated. It was demonstrated that the effect of enhancement of the signal intensity of Raman scattering from porous silicon compared with the signal intensity from the substrate is associated with the presence of micrometer-size pores in the samples. A model making it possible to explain this enhancement, the signal shape, and the coincidence of the signal from the porous layer by the shape and location with the line from the Si substrate is suggested.