Metastable acceptor centers in boron implanted silicon

The evolution of the electrical activation with the annealing time in B1 implanted (5.0 31014 cm22, 50 keV! Si was studied as a function of the annealing temperature. Electrical activation yields of 15%–30% were observed after annealing for 2 s at temperatures above 550 °C. Prolonging the annealing time from 2 to 900 s we observed that the electrical activation evolves differently according to the temperature: ~i! at 550 °C,T,700 °C it decreases toward an equilibrium level, ~ii! at 700 °C,T,800 °C it decreases during the first minutes and subsequently increases again, and ~iii! at temperatures ,550 °C or T.800 °C it increases continuously. In order to explain the carrier removal observed during annealing at 550–800 °C we proposed that metastable acceptor centers are formed during the B1 implantation and/or the initial period of the annealing time. Interaction of Si self-interstitial atoms with these centers leads to their neutralization and/or dissociation with consequent decreasing of the carrier concentration

Magnetoresistance of doped silicon

We have performed longitudinal magnetoresistance measurements on heavily n-doped silicon for donor concentrations exceeding the critical value for the metal-non-metal transition. The results are compared to those from a many-body theory where the donor-electrons are assumed to reside at the bottom of the many-valley conduction band of the host. Good qualitative agreement between theory and experiment is obtained.Comment: 7 pages, 8 figure

Enhanced damage accumulation in carbon implanted silicon

The accumulation of damage in Si implanted with 12C+ was investigated experimentally using aligned Rutherford backscattering analysis. The damage protiles in Si implanted with 12C+ or 11B+ at 50 keV to the same doses and dose rate were compared. It was found that the damage accumulates at a noticeably higher rate by 12C+ implantation than by 11B+, especially for doses >2X 1Or5 cmm2. In order to explain our results we suggest that self-interstitial Si atoms are captured by the implanted C atoms, forming complex defects which are stable at room temperature

Electrical isolation of GaN by MeV ion irradiation

The evolution of sheet resistance of n-type GaN epilayers exposed to irradiation with MeV H, Li, C, and O ions is studied in situ. Results show that the threshold dose necessary for complete isolation linearly depends on the original free electron concentration and reciprocally depends on the number of atomic displacements produced by ion irradiation. Furthermore, such isolation is stable to rapid thermal annealing at temperatures up to 900 °C. In addition to providing a better understanding of the physical mechanisms responsible for electrical isolation, these results can be used for choosing implant conditions necessary for an effective electrical isolation of GaN-based devices

Estudo da implantação de As a baixas energias em Si e SIMOX

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Heavily n-doped Ge : low-temperature magnetoresistance properties on the metallic side of the metal–nonmetal transition

We report here an experimental and theoretical study on the magnetoresistance properties of heavily phosphorous doped germanium on the metallic side of the metal–nonmetal transition. An anomalous regime, formed by negative values of the magnetoresistance, was observed by performing low-temperature measurements and explained within the generalized Drude model, due to the many-body effects. It reveals a key mechanism behind the magnetoresistance properties at low temperatures and, therefore, constitutes a path to its manipulation in such materials of great interest in fundamental physics and technological applications

Preparação de membranas de silício auto-sustentáveis

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Defect-Free and Annealing Influences in P3HT Organic Field-Effect Transistor Performance

Organic field effect transistors were fabricated using photolithography and plasma etching technique with defect free Poly(3-hexylthiophene) (P3HT) and P3HT 90 % regioregular with different temperatures of annealing at normal ambient. PVA (Poly - vinyl Alcohol) was used as gate dielectric and Ni contacts formed the source and drain electrodes. Improvement of transistor stability and increase of carrier mobility with use of defect free P3HT was reached. The stability enhancement permitted an higher ION current during stress. The auto-encapsulation process involved in the process of fabrication permits an ambient stability, in which the transistors do not degrade due to moisture and oxygen. All the transistors operate at low voltages, due to the high dielectric constant of PVA, being adequate to actual applications. P3HT films deposited in the same conditions as in the active area of the transistors were analyzed by photoluminescence and XRR measurements and it was observed an improvement in crystallinity for the defect free P3HT annealed at lower temperatures, which corroborates the results observed in the transistors characteristics

Effects of carbon on dynamic annealing and on electrical activation of dopants in silicon substrate

The effect of C on the implantation damage accumulation in Si crystal and on the electrical T activation of dopants was investigated, using RBS-channeling technique, sheet resistivity and Hall measurements. The damage profiles in Si implanted with 12C+ or llBS at 50 keV to the same doses and dose rate were compared. It was found that the damage accumulates at a noticeably higher rate during 12c+im plantation than in the case of "B+, especially for doses > 2 x I0l5 ~rn-~I t. i s shown that the dynamic annealing is strongly reduced in regions doped with C. In addition, the influence of C on the electrical activation of the co-implanted dopant is discussed for the case of B and Bi. A model considering an interaction between C and Si self-interstitial (Sir) atoms during implantation and the subsequent thermal annealing is proposed to explain the enhanced implantation damage accumulation and the activation behavior of B in samples co-implanted with

Cálculos e desenvolvimento de transistores n-mos e p-mos usando os softwares de modelagem SUPREM e PISCES

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