E. I. Shek

Photoluminescence and structural defects in erbium-implanted silicon annealed at high temperature

The behavior of luminescence spectra and structural defects in single crystal Czochralski silicon after erbium implantation at 1 MeV energy and 1×1013 cm−2 dose with subsequent annealing at 1100 °C for 0.25–3 h in an argon or chlorine-containing ambience was studied by photoluminescence (PL), transmission electron microscopy, and chemical etching/Nomarski microscopy. We have found that annealing in the chlorine-containing ambience gives rise to dislocation loops and pure edge dislocations with dominant dislocation-related lines in the PL spectrum. Pure edge dislocations are responsible for the appearance of the lines. The Er-related lines due to the intra-4f shell transitions in the rare-earth ions dominate in the PL spectra and no structural defects are observed after annealing in argon. The observed differences in the optical and structural properties of Si:Er are associated with intrinsic point defects generated during the implantation and annealing.

Influence of Extended Structural Defects on the Characteristics of Electroluminescence in Efficient Silicon Light-Emitting Diodes

We report our results on electroluminescence in the range of 1.0-1.6 μm, structural defects and electrophysical properties of light-emitting diodes f abricated by boron ion implantation into n-Si substrates at different concentrations of the doping impuri ty with a subsequent thermal annealing at 700-1200 ° in argon or a chlorine-containing atmosphere. A band-to-band emission peak dominates in the luminescence spectra of all the samples at 80-500 K. The quantum efficiency of the band-to-band luminescence and the minority carrier lifetime i ncrease with annealing temperature to 1100 ° in argon, with the efficiency practically proportional to the life time. A similar correlation was observed after annealing in the chlorineco taining atmosphere. The maximum internal quantum efficiency (~ 0.4 %) was registered after annealing in argon at 1100 ° , when there are no extended structural defects. Rod-like defects, part ial Frank and perfect prismatic dislocation loops are formed after annealing at lower temperature s. Th ir type, sizes and density are governed by the annealing temperature. No correlation between the quant um efficiency and the defect structure was revealed with the variation of the annea li g temperature. The analysis of the experimental data shows that the influence of extended defects on the band-to-band luminescence is most likely to be due to the incorporation and/or gettering of non-radiat ive recombination centers rather than to preventing the diffusion of charge carriers to the centers. The effect of the annealing conditions and doping impurity concentration in the substrates on the param ete s of defect-related emission lines has also been studied. The most intensive defect-re lated lectroluminescence at room temperature is observed after annealing at 700 ° in diodes with a lower concentration.

Dislocation-related luminescence in single-crystal silicon subjected to silicon ion implantation and subsequent annealing

Implantation of silicon ions with an energy of 100 keV at a dose of 1 × 1017 cm−2 into n-type floatzone Si does not lead to the formation of an amorphous layer. Subsequent annealing in a chlorine-containing atmosphere at 1100°C gives rise to dislocation-related luminescence. The intensity of the dominant D1 line peaked at a wavelength of ∼1.54 μm grows as the annealing time is increased from 15 to 60 min.

Dislocation-related luminescence in silicon, caused by implantation of oxygen ions and subsequent annealing

Multiple implantation of oxygen ions with energies of 0.1–1.5 MeV at doses of 7 × 1013−2 × 1014 cm−2 and subsequent annealing in a chlorine-containing atmosphere at 900°C for 4 h give rise to dislocation-related luminescence in p-Si. A p → n conductivity-type conversion is also observed in this case in the surface layer of Si, which indicates that electrically active donor centers are formed in the process. Preliminary heat treatment of wafers covered with an erbium-doped film of tetraethoxysilane (TEOS) in argon at 1250°C for 1 h does not preclude the appearance of dislocation-related luminescence, but affects the parameters of the dislocation-related lines (peak positions and intensities).

Correlation between defect structure and luminescence spectra in monocrystalline erbium-implanted silicon

The transformation of structural defects and photoluminescence (PL) spectra of n- and p-type Cz-Si after implantation with erbium ions at 1 MeV energy to doses of 1 × 1013 and 1 × 1014 cm−2 followed by annealing at 620–1100°C for 0.25–3.0 h in chlorine-containing atmosphere or oxygen have been studied by transmission electron microscopy, optical microscopy in combination with selective chemical etching, and PL. For the doses used, annealing at a temperature lower than 1100°C leads to the formation of different extended defects (partial Frank or perfect prismatic dislocation loops) of submicron sizes which do not prevent the appearance of Er-related lines and do not give rise to dislocation-related lines in the PL spectrum. In contrast, high-temperature annealing at 1100°C results in the development of similar three-dimensional networks of pure edge dislocations with a density of ~107 cm−2. These dislocations are responsible for the appearance of quite intensive dislocation-related luminescence (DRL). For high-dose implantation, when annealing at 1100°C is used, the same dislocation networks have been found to form in the n- and p-Si wafers with different low-temperature annealing stages (if any). However, all these parameters exert the peculiar influence upon the intensity of DRL lines.

Extended defects in Si wafers implanted with ions of rare-earth elements

Abstract Structural defects arising in Cz–Si wafers after implantation with high-energy ions of rare-earth elements (Er, Ho, Dy) and annealing in a chlorine-containing ambience were studied by transmission electron microscopy and chemical etching/Nomarski microscopy. Regularities of extended defect formation in dependence on implant and annealing conditions as well as evolution of structural defect patterns during thermal annealing have been established.

Electrically active centers formed in silicon during the high-temperature diffusion of boron and aluminum

The parameters of electrically active centers formed during the high-temperature diffusion of boron and aluminum into silicon in various media are studied by the Hall method and capacitance spectroscopy. It is found that the variation in the resistivity of the n base of the structures with p-n junctions fabricated in the study is controlled by the formation of three donor levels Q1, E4, and Q3 with the energies Ec - 0.31, Ec - 0.27, and Ec - 0.16 eV. Diffusion in a chlorine-containing atmosphere introduces only a single level E4, but its concentration is 2.5 times lower, compared with diffusion in air. The values of the ionization energy of the Q3 level, measured under equilibrium (Hall effect) and nonequilibrium (capacitance spectroscopy) conditions, almost coincide. The deepest level E1 with an energy of Ec - 0.54 eV, formed upon diffusion in both media, has no effect on the resistivity in the n base of the structures.

Electroluminescent properties of strained p-Si LEDs

Electroluminescence (EL) in the range 1.0–1.65 μm from LEDs strained by four-point bending at 700°C has been studied at currents up to 400 mA. The LEDs are fabricated by implantation of B and P ions into p-Si wafers grown by the floating-zone (FZ-Si) and Czochralski (Cz-Si) methods followed by annealing at 700 and 1100°C. The intensity of dislocation-related EL is higher in the FZ-Si than in the Cz-Si samples. It is also higher in the samples subjected to low-temperature post-implantation annealing than in those that underwent the same annealing at a high-temperature. The current-related transformation of the FZ-Si EL spectra is described well by eight Gaussian lines. The peak positions are 1.22, 1.244, 1.26, 1.316, 1.38, 1.42, 1.52 and 1.544 μm, and they are independent of current. Dependences of the integral intensity and line width on current are studied.

Si:Si LEDs with room-temperature dislocation-related luminescence

Silicon-based light-emitting diodes (LEDs) fabricated by the Si-ion implantation and chemical-vapor deposition methods are studied. Room-temperature dislocation-related electroluminescence (EL) is observed in LEDs based on n-Si. In LEDs based on p-Si, the EL is quenched at temperatures higher than 220 K. The EL-excitation efficiencies are measured for the D1 line at room temperature and the D1 and D4 lines at liquid-nitrogen temperature.

Silicon LEDs with room-temperature dislocation-related luminescence, fabricated by erbium ion implantation and chemical-vapor deposition of polycrystalline silicon layers heavily doped with boron and phosphorus

Light-emitting diodes (LEDs) have been fabricated in which optically active centers are formed by implantation of erbium ions into silicon and subsequent high-temperature annealing in an oxidizing atmosphere and the p-n junction and the ohmic contact are formed by chemical vapor deposition of polycrystalline silicon layers doped with boron and phosphorus, respectively. The luminescent properties of the LEDs have been studied. Use of polycrystalline layers makes it possible to eliminate the losses in the bulk of the light-emitting Si:Er layer. These losses are inevitable if the conventional ion implantation and diffusion methods are employed. At 80 K, the variation of electroluminescence spectra in the spectral range of the dislocation-related luminescence with the drive current is well described if the spectrum is decomposed into three Gaussian components whose peak positions and widths are current-independent and amplitudes linearly increase with the current. At 300 K, a single peak is observed in the spectral range of the dislocation-related luminescence at ∼1.6 μm.