Moissei K. Sheinkman

Ultrasound regeneration of EL2 centres in GaAs

The new effect of ultrasound-stimulated regeneration of the ground state of EL2 centres is observed and investigated. A regeneration transition, metastable (EL2*)-to-ground (EL20), is caused by ultrasound vibrations induced in a GaAs wafer at a temperature 105-120 K after bleaching of EL2 centres with 1.2 eV light. The EL2-related absorption band and the luminescence band with a maximum of 0.64 eV are examined. The kinetics of the ultrasound EL2 regeneration and the dependence of the number of regenerated EL2 centres on ultrasound strain are measured at different temperatures. Relevant mechanisms for the regeneration are discussed, and the arguments in favour of the dislocation model are presented.

Excitation mechanism of porous silicon luminescence: the role of sensitizers

Abstract The correlation of the photoluminescence and photoluminescence excitation spectra of porous silicon in the as-prepared, etched and low-temperature annealed states are studied. The results obtained are explained within the model of photoluminescence excitation by surface sensitizers and subsequent transfer of the excitation to the porous silicon.

Manifestation of effective-mass states of secondary minima in the persistent photoconductivity related to the DX centre in

The correlation of persistent photoconductivity and photo-Hall studies of Sn- and Si-doped layers of compositions with previous photo-EPR results obtained on the same samples shows the importance of hydrogenic effective-mass states derived from secondary conduction band minima in highly () doped samples. The Fermi level pinning after low-temperature photoexcitation in direct-gap material by the resonant level in the case of Sn-doped samples, directly demonstrated by its EPR detection, explains the difference in the spin and carrier concentrations observed as well as the different kinetics for the relaxation into the initial state. The consideration of this state allows further an interpretation of the nonmonotonic changes of the free-electron mobility with the photon flux observed in highly doped () samples.

Stability of Emission Properties of Silicon Nanostructures

The aging process of silicon nanostructures obtained by magnetron sputtering and electrochemical etching is investigated by photoluminescence and Raman scattering methods. It is shown that oxidation of silicon crystallites takes place in both types of structures and results in appearance of additional emission bands. However the degree of oxidation in etched structures exceeds significantly this value for sputtered samples. It is found that the intensity and spectral position of the emission band caused by exciton recombination in Si crystallites do not change practically during aging in sputtered structures in contrast to etched ones. It is shown that the oxidation of silicon amorphous phase occur during aging in sputtered structures.

Influence of subthreshold ultrasound treatment on the recombination properties of dislocations in GexSi1-x-Si heterostructures

The effect of subthreshold ultrasound treatment on the dislocation-related photoluminescence (D bands) and EBIC contrast is studied in n-GexS1-x-Si heterostructures. It is shown that ultrasound treatment causes both an increase in the intensity of the D1 and D2 bands and changes in their linear polarization. The proposed mechanisms for the phenomena include (i) ultrasound-stimulated dislocation gettering of the impurities and (ii) the reorientation of the impurities in order to reduce strain near the dislocation.

Semiconductor Ultrasound Treatment

The sections in this article are 1 UST Method and Apparatus 2 Fundamentals: UST Phenomena and Mechanisms 3 UST Applications 4 Summary and Conclusion

Generation of metastable shallow donors induced by cooling in hexagonal II-VI semiconductors

A highly conductive layer is found to arise on a (0001) plane of CdS, CdSe and CdSSe crystals under cooling in darkness from 300 to 77 K. This effect is shown to be caused by the increase of free electron density in a thin (500-100 AA) subsurface layer. At 77 K, the free electron density in this layer reaches approximately 1018 cm-3. Detailed investigations of the dark conductivity, photoconductivity, Hall effect and bound exciton luminescence lead to the conclusion that the increase of conductivity is due to creation of metastable donors. This effect is supposed to be stimulated by both a pyroelectric field and mechanical stresses arising under cooling.