P. E. Pak

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.

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.

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.

Mechanism of erbium electroluminescence in hydrogenated amorph silicon

The mechanism of the electroluminescence of erbium under a reverse bias in structures based on hydrogenated amorphous silicon is studied. Erbium ions are excited through an Auger process, in which conduction electrons are trapped by neutral dangling bonds (D0 centers) located near the erbium ions. A stationary current through the structure is sustained by a reverse process involving the thermally stimulated tunneling emission of electrons by negatively charged dangling-bond defects (D0 centers) into the conduction band of the amorphous matrix.

Erbium electroluminescence excitation in amorphous hydrogenated silicon under thermally stimulated deep-center tunneling ionization

A study of the electroluminescence of erbium-doped, amorphous hydrogenated silicon, a-Si:H 〈Er〉, is reported. It has been found that the electroluminescence intensity at the wavelength λ=1.54 µm corresponding to the 4I13/2→4I15/2 intra-4f shell transition in Er passes through a maximum near room temperature. The unusual temperature and field dependences of the electroluminescence indicate electric-field induced multi-phonon tunneling emission of electrons from deep centers. The electroluminescence of Er3+ ions is due to their becoming excited as conduction-band electrons are captured by neutral dangling bonds (D0 centers), which form when erbium is incorporated into the amorphous matrix. This Auger process transforms the center from its neutral state, D0, to a negatively charged state, D−, and the energy released in the capture is transferred by Coulomb interaction into the erbium-ion 4f shell. The steady-state current through the electroluminescent structure is supported by the reverse process of multi-phonon tunneling-electron emission from the D− center to the conduction band. The proposed theoretical model is in a good agreement with experimental data.

Influence of impurities on luminescence of Er-doped silicon structures

The investigation of photo- and electroluminescence in erbium-doped silicon additionally co-implanted with oxygen, phosphorus and boron show an enhancement of the 1.54 micrometers line luminescence intensity in Si:Er:O and Si:Er:O:P and an intensity quenching in Si:Er:O:B as compared with Si:Er. A threshold in dependence of defect-related line electroluminescence signal on drive current is observed too. A model describing the observed variations of luminescence spectra in dependence on implantation and annealing conditions is presented. Optimization of technological regimes resulted in formation of light emitting erbium-doped silicon structures operating at room temperature.

Room-temperature photoluminescence of erbium-doped amorphous hydrogenated silicon

Photoluminescence of erbium-doped hydrogenated amorphous silicon was observed and compared with that of crystalline erbium-doped silicon. It is shown that a-Si:H:Er exhibits efficient room-temperature photoluminescence at 1.537 micrometer which is as strong as the emission from optimized c-Si:Er at 2 K. Practically no temperature quenching of the emission intensity in the range 2 - 300 K is observed. Saturation of erbium luminescence on increase of excitation level occurs at higher intensities of pumping beam than in c-Si:Er indicating shorter radiation lifetime of erbium ions.

Electroluminescence and excitation mechanism of erbium ions in erbium-doped crystalline silicon

Electroluminescence (EL) of photodiodes fabricated from erbium-implanted silicon is studied at direct bias of p-n junction. A correlation between the intensities of EL of free excitons and erbium ions is found in dependence on pumping current. A model of f-shell excitation of optically active erbium ions is proposed basing on the assumption that the excitation of erbium ions occurs via capture of free excitons on neutral donor formed by erbium-oxygen complex with a subsequent auger-excitation of f-shell of erbium ion during recombination of a bound exciton. The model proposed permits us to described the experimental results.