M. S. Bresler

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.

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.

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.

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.

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.

Electron paramagnetic resonance in Kondo insulators

This review is devoted to the application of electron paramagnetic resonance (EPR) in the study of fluctuating-valence materials, which are characterized by a narrow gap in the electron energy spectrum (Kondo insulators or Kondo semiconductors). The authors’ papers on studying classical objects of this field of solid-state physics, SmB6 and YbB12, are considered as an illustration of the potentiality of the EPR method. Temperature dependences of the gap width in these materials were obtained, the static and dynamic Jahn-Teller effects on Sm3+ ions in SmB6 were detected, and the formation of Yb3+ ion pairs and the spontaneous breaking of cubic symmetry in YbB12 were observed. The results obtained indicate that preference should be given to the exciton-polaron model developed by Kikoin et al. for the ground state of Kondo insulators.

Effective excitation cross section of erbium in amorphous hydrogenated silicon under optical pumping

The effective excitation cross section of erbium embedded in an amorphous silicon matrix and the total lifetime of erbium ions in the excited state are determined by measuring the photoluminescence rise time of erbium ions under pulsed excitation of erbium-doped amorphous hydrogenated silicon. An analysis of the rate equations describing the excitation and deexcitation of erbium ions in a semiconducting matrix sheds light on the physical meaning of the effective excitation cross section. It is shown that measurement of the effective excitation cross section permits evaluation of the concentration of optically active erbium ions in the amorphous silicon matrix.

Electroluminescence efficiency of silicon diodes

The intrinsic electroluminescence (EL) of a silicon light-emitting diode with a forward-biased p-n junction is studied. The substantial enhancement of the integrated EL intensity observed with the temperature increasing from the liquid-nitrogen to room-temperature level, which is paralleled by an increase in the EL decay time when the current through the diode is terminated, indicates thermal suppression of the nonradiative recombination channel associated with deep traps. A simple model developed by us for the radiative processes occurring in a p-n junction offers an interpretation for all the experimental data obtained. It is shown that the internal quantum efficiency of the EL may reach a level of a few percent under optimal doping of the diode p and n regions.

Edge electroluminescence of silicon: An amorphous-silicon-crystalline-silicon heterostructure

Silicon edge electroluminescence (EL) was observed on an amorphous-silicon-crystalline-silicon heterostructure (a-Si: H(n)/c-Si(p)) in the temperature range from 77 to 300 K. The room-temperature EL internal quantum efficiency of the heterostructure under study was found to be about 0.1%. A theoretical analysis of the emissive properties of the a-Si: H(n)/c-Si(p) heterostructure was made in terms of the model of an abrupt planar p-n junction and showed that, for optimal doping, the internal quantum efficiency of the EL may be as high as a few percent at a modulation frequency of about 50 kHz.