O. B. Gusev

Room‐temperature photoluminescence of erbium‐doped hydrogenated amorphous silicon

A comparison of the photoluminescence of Er‐doped hydrogenated amorphous silicon and crystalline silicon a‐Si:H(Er) and c‐Si(Er), is presented. It is shown that a‐Si:H(Er) exhibits efficient room‐temperature photoluminescence at 1.537 μm which is as strong as the emission from optimized c‐Si(Er) at 2 K. Most remarkably, there is practically no temperature quenching of the emission intensity in the range 2–300 K. The experiments suggest that the lifetime connected with the Er‐induced emission is considerably shorter in a‐Si:H(Er) than in c‐Si(Er) which may be responsible for the different dependences of the photoluminescence intensity on the temperature, chopping frequency, and excitation power.

Room-temperature electroluminescence of erbium-doped amorphous hydrogenated silicon

We have observed strong room-temperature electroluminescence at 1.54 μm induced by erbium ions in amorphous hydrogenated silicon (a-Si:H). The device consisted of an Al/a-Si:H(Er)/n-c-Si/Al structure. A mechanism for electronic excitation of the erbium ions in the amorphous matrix is proposed that is based on defect-related Auger excitation.

Light emission from silicon nanocrystals

The main experimental results of studies of the photoluminescence of silicon nanocrystals and theoretical methods developed for the description of optical processes occurring in them are reviewed. Special attention is focused on silicon nanocrystals in the SiO2 matrix that were the object of most of the studies. Two fundamental theoretical methods described in detail are the multiband effective-mass method and the tight-binding method which have found wide application in simulating various processes occurring in nanostructures. A phenomenological model for excitons self-trapped on the surface of oxidized silicon nanocrystals, which has been recently developed on the basis of experimental results obtained by femtosecond spectroscopy, is reported.

Defect-related Auger excitation of erbium ions in amorphous silicon

A transition probability for defect-related Auger excitation (DRAE) of rare-earth ion inserted into amorphous matrix is calculated. The result is applied to excitation of an erbium ion in amorphous silicon occurring via capture of an electron by the dangling bond (D) defect. We have demonstrated high efficiency of the DRAE process which ensures photo- and electroluminescence of erbium ions in amorphous silicon matrix. It is shown that the temperature quenching of erbium luminescence in amorphous silicon is controlled by competition of the DRAE and the multiphonon nonradiative transitions.

Energy transfer between silicon nanocrystals

It is shown that the energy migration between silicon nanocrystals embedded into a silicon dioxide host is caused by the “nonresonant” dipole-dipole interaction. This process is efficient only for a part of small nanocrystals among the whole ensemble of nanocrystals. The nonresonant dipole-dipole energy transfer has such a feature as the emission of two optical phonons at each step of the process. The time of the excitation transfer has been experimentally determined for nanocrystals 1.5 nm in size existing in the ensemble of nanocrystals with a density of 1018 cm−3 and the size distribution with a standard deviation of 20%. A value of 30 μs obtained for this time is in good agreement with the performed theoretical estimation.

Efficient Auger-excitation of erbium electroluminescence in reversely-biased silicon structures

In p–n junctions based on c-Si:Er, we have observed strongly efficient excitation of erbium electroluminescence at 1.54 μm. Excitation of erbium ions is accompanied by strong recombination of free carriers indicating a participation of an Auger mechanism. A possible excitation mechanism is proposed which is the Auger recombination of electrons occupying the upper subband of the conduction band with free holes in the valence band, whereas the energy of the recombination process is transferred by Coulomb interaction to 4f electrons of an erbium ion transmitting it to the second excited state 4I11/2 (excitation energy 1.26 eV). The observed three-level excitation of erbium ions is promising for the development of a Si:Er laser.

Luminescence of erbium in amorphous hydrogenated silicon obtained by the glow-discharge method

We report the first observation of efficient room-temperature photoluminescence of erbium in amorphous hydrogenated silicon prepared by the plasma chemical-deposition method.

Room-temperature electroluminescence of Er-doped hydrogenated amorphous silicon

Abstract We have observed room-temperature erbium-ion electroluminescence in erbium-doped amorphous silicon. Electrical conduction through the structure is controlled by thermally activated ionization of deep D − defects in an electric field and the reverse process of capture of mobile electrons by D 0 states. Defect-related Auger excitation (DRAE) is responsible for excitation of erbium ions located close to dangling-bond defects. Our experimental data are consistent with the mechanisms proposed.

Effect of electric field in the course of obtaining a-SiOx:H(Er, O) films by dc magnetron sputtering on their composition and photoluminescence intensity of erbium ions

The effect of electric field on the elemental composition and photoluminescence of films of amorphous hydrogenated silicon doped with erbium and oxygen (a-SiOx:H(Er, O)) in the course of obtaining these films by dc magnetron sputtering is studied. Two series of films were studied in relation to the electric-field strength in the magnetron, the area of the metallic erbium target, and oxygen content in the working chamber. The first series of films was obtained using an electrically insulated substrate holder, and the second series was obtained with a positive potential at the substrate holder with respect to the cathode. It is shown that, although the character of variation in the elemental composition and photoluminescence intensity for erbium Er3+ ions differ appreciably in the films of the two series, both of these factors are determined, as a result, by the processes of sputtering oxidation of the Si and Er targets that represent the cathode.

Mechanisms of excitation and thermal quenching of erbium-ion luminescence in crystalline and amorphous silicon

A short review is presented of the erbium-ion excitation mechanisms in crystalline and amorphous silicon and of the processes governing thermal quenching of erbium luminescence in these materials, which draws both from the studies carried out by the present authors and from available literature data.