T. Gebel

Bright green electroluminescence from Tb3+ in silicon metal-oxide-semiconductor devices

Bright green electroluminescence with luminance up to 2800cd∕m2 is reported from indium-tin-oxide∕SiO2:Tb∕Si metal-oxide-semiconductor devices. The SiO2:Tb3+ gate oxide was prepared by thermal oxidation followed by Tb+ implantation. Electroluminescence and photoluminescence properties were studied with variations of the Tb3+ ion concentration and the annealing temperature. The optimized device shows a high external quantum efficiency of 16% and a luminous efficiency of 2.1lm∕W. The excitation processes of the strong green electroluminescence are attributed to the impact excitation of the Tb3+ luminescent centers by hot electrons and the subsequent crossrelaxation from D35 to D45 energy levels. Light-emitting devices with micrometer size fabricated by the standard metal-oxide-semiconductor technology are demonstrated.

Advanced Thermal Processing of Ultrashallow Implanted Junctions Using Flash Lamp Annealing

The use of flash lamp annealing for ultrashallow junction formation in silicon has been described. Low energy boron and arsenic implants have been heat-treated in this way using peak temperatures in the range of 1100 to 1300°C and effective anneal times of 20 and 3 ms. Secondary ion mass spectrometry and four-point probe measurements have been undertaken to determine the junction depth and the sheet resistance, respectively. Optimum processing conditions have been identified, under which one can obtain combinations of junction depth and sheet resistance values that meet the 90 nm technology node requirements and beyond.

Efficient ultraviolet electroluminescence from a Gd-implanted silicon metal-oxide-semiconductor device

Strong ultraviolet electroluminescence with an external quantum efficiency above 1% is observed from an indium-tin oxide/SiO2:Gd∕Si metal–oxide–semiconductor structure. The SiO2:Gd active layer is prepared by thermal oxidation followed by Gd+ implantation and annealing. The electroluminescence spectra show a sharp peak at 316nm from the P7∕26 to S7∕28 transition of Gd3+ ions. Micrometer-sized electroluminescent devices are demonstrated.

Light emission and charge trapping in Er-doped silicon dioxide films containing silicon nanocrystals

The processes of electro- (EL) and photoluminescence (PL) and charge trapping in Er-implanted SiO2 containing silicon nanoclusters have been studied. It is shown that in Er-doped SiO2 with an excess of silicon nanoclusters of 10 at. %, a strong energy transfer from silicon nanoclusters results in a ten-fold increase of the PL peak at 1540 nm from Er luminescent centers, whereas the EL is strongly quenched by the excess silicon nanoclusters. It is further shown that the implantation of Er creates in the oxide positive charge traps with a giant cross section (σh0>10−13cm2). Introducing subsequent silicon nanocrystals in the oxide leads to the formation of negative charge traps of a giant cross section (σe0>10−13cm2). The possible reason for the EL quenching in the Er-doped SiO2 by silicon nanoclusters is discussed.

Increase of blue electroluminescence from Ce-doped SiO2 layers through sensitization by Gd3+ ions

Efficient blue electroluminescence peak at around 440nm with a maximum output power density of 34mW∕cm2 was obtained from Ce and Gd coimplanted metal-oxide-semiconductor light emitting devices. Energy transfer from Gd3+ to Ce3+ ions was observed during the excitation process, leading to a more than threefold increase of the external quantum efficiency of the blue Ce3+ luminescence up to 1.8%. This is evidenced by the increase of the excitation cross section of Ce3+ ions from 4.8×10−13to3.5×10−12cm2 and the simultaneous reduction of the decay time and the impact cross section of Gd3+ ions.Efficient blue electroluminescence peak at around 440nm with a maximum output power density of 34mW∕cm2 was obtained from Ce and Gd coimplanted metal-oxide-semiconductor light emitting devices. Energy transfer from Gd3+ to Ce3+ ions was observed during the excitation process, leading to a more than threefold increase of the external quantum efficiency of the blue Ce3+ luminescence up to 1.8%. This is evidenced by the increase of the excitation cross section of Ce3+ ions from 4.8×10−13to3.5×10−12cm2 and the simultaneous reduction of the decay time and the impact cross section of Gd3+ ions.

Trapping of negative and positive charges in Ge+ ion implanted silicon dioxide layers subjected to high-field electron injection

Negative and positive charge trapping in a constant current regime under high-field electron injection both from Al electrode and Si substrate in high-dose Ge+ ion implanted and then rapid thermal annealed thin-film dioxide has been studied. Negatively charged traps as well as generated positive charges with effective capture cross sections of σ1(−)>10−14 cm2, σ2(−)≈1.8×10−15, σ3(−)≈2×10−16, and σ4(−)≈3×10−18 cm2, as well as σ1(+)≈(5–7)×10−15 and σ2(+)≈3.3×10−16 cm2, respectively, are shown to be introduced into the oxide layer. A good correlation of the electron trap concentration with a cross section of σ1(−)>10−14 cm2 and the concentration of the implanted Ge atoms, determined by Rutherford backscattering spectrometry inside the oxide, is observed. The decrease of Ge concentration within the oxide layer with increasing duration of rapid thermal annealing is associated with Ge atom outdiffusion from the oxide at high-temperature annealing. The generated positive charge is shown to be collected near the ...

Electroluminescence properties of the Gd3+ ultraviolet luminescent centers in SiO2 gate oxide layers

Electroluminescence (EL) properties in the ultraviolet (UV) range were studied on Gd-implanted indium tin oxide/SiO2:Gd∕Si metal-oxide-semiconductor light emitting devices. The efficient UV line at 316nm from Gd3+ centers shows a maximum power density of 2mW∕cm2 and a quantum efficiency above 5%. The Gd3+ luminescent center has an excitation cross section above 7.4×10−15cm2 with an EL decay time around 1.6ms at a Gd concentration of 3%. A decrease of the EL efficiency is observed by a cross relaxation at a high Gd concentration and by clustering of Gd atoms at an annealing temperature of 1000°C. A strong quenching of the UV EL due to electron trapping around optically active Gd3+ centers is observed during the injection of hot electrons.

Memory properties of Si+ implanted gate oxides: from MOS capacitors to nvSRAM

Charge storage properties of 20–30 nm gate oxides implanted with Si þ ions are investigated using MOS capacitors, single transistor structures and a non-volatile memory. The observed programming window can reach several volts for programming with electric fields of about 4–7 MV/cm. The structures exhibit good retention (250 C, 280 h) and the endurance (>10 6 w/e-cycles) considerably exceeds the typical values of present EEPROM technologies. The capability of Si implanted SiO2 films as gate dielectrics for a real non-volatile memory is demonstrated for the first time by a 256 K-non-volatile static random access memory showing a programming window of larger than 1 V. 2002 Elsevier Science Ltd. All rights reserved.

Charge trapping in light-emitting SiO2 layers implanted with Ge+ ions

The trapping effects of negative and positive charge in Ge-enriched SiO2 layers during high-field electron injection from the Si substrate of Al–SiO2–Si structures are studied. The capture cross section and the concentration of negatively and positively charged traps are estimated and the location of the positively charged traps is determined. It is shown that increasing rapid thermal annealing time from 6 to 150 s at 1000 °C leads to an enhanced diffusion of Ge towards the SiO2–Si interface and an increase in negatively and positively charged trap concentration. The mechanisms of the trap generation are discussed.

Ion beam synthesized nanoclusters for silicon-based light emission

Abstract Strong blue and violet photoluminescence (PL) and electroluminescence (EL) at room temperature has been achieved from thin SiO 2 layers implanted with group IV elements. Thermally grown SiO 2 films with thicknesses between 130 and 500 nm were implanted with Si + , Ge + or Sn + ions followed by different annealing procedures. Based on PL and PL excitation spectra we tentatively interpret the blue–violet PL as due to a T 1 →S 0 transition of an oxygen deficiency center. The strong EL is well visible with the naked eye and reaches a power efficiency of up to 5×10 −3 for Ge. Whereas the EL intensity shows a linear dependence on the injection current for Ge-rich layers, the shape of the EL spectrum remains unchanged. It was found that the I – V characteristics shift to lower applied electric fields with increasing implantation fluence. Furthermore, it is assumed that the luminescence centers will be excited either by field ionization or by the scattering of hot electrons. Finally, the suitability of ion implanted silicon dioxide layers for optoelectronic applications is discussed.