Features of the formation of thermal donors in silicon under elastic tensile stress

The formation process of electrically active oxygen-containing complexes (thermal donors) in silicon is investigated at the initial stage of thermal treatment at T < 500°C under elastic tensile stress σ = 1 GPa. It is shown that, under these conditions, the formation of singly charged donor centers is observed in silicon when the oxygen concentration is (3–5) × 10¹⁷ cm^?3. When the oxygen concentration is 9 × 10¹⁷ cm^?3, doubly charged donor centers form. The depth profile of thermal donors is found in the samples studied.     

Structures of thermal double donors in silicon

Accurate total-energy calculations are used to study the structures and formation energies of oxygen chains as models for thermal double donors (TDD's) in Si. We find that the first three TDD's (TDD0-TDD2) consist of one four-member ring, with one or two adjacent interstitial O atoms. These metastable TDD's form bistable negative-U systems with the corresponding stable, electrically inactive staggered structures. The TDD3-TDD7 structures are found to consist of four-member rings with adjacent interstitial O atoms at both ends. The TDD's with a central "di-Y-lid" core are found to become energetically competitive with the four-member ring TDD's only for clusters larger than ten O atoms.     

Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing

A novel pulsed rapid thermal processing (PRTP) method has been used for realizing solid-phase crystallization of amorphous silicon films prepared by plasma-enhanced chemical vapour deposition.The microstructure and surface morphology of the crystallized films were investigated using x-ray diffraction and atomic force microscopy.The results indicate that PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural quality,such as large grain size,small lattice microstrain and smooth surface morphology on low-cost glass substrates.     

Aggregation kinetics of thermal double donors in silicon

A general kinetic model based on accurate density-functional-theoretic total-energy calculations is introduced to describe the aggregation kinetics of oxygen-related thermal double donors (TDD's) in silicon. The calculated kinetics, which incorporates the reactions of associations, dissociations, and isomerizations of all relevant oxygen complexes, is in agreement with experimental annealing studies. The aggregation of TDD's takes place through parallel-consecutive reactions where both mobile oxygen dimers and fast migrating chainlike TDD's capture interstitial oxygen atoms.     

Shallow thermal donors in nitrogen-doped silicon single crystals

Czochralski-grown nitrogen-doped silicon crystals contain shallow thermal donors (STD) which are not present in reference crystals. In the course of annealing at 600 or 650°C, the STD concentration reaches saturation and this concentration scales with nitrogen content N as N^1/2. This implies that an STD includes only one nitrogen atom and that the most likely model of the STD defect is the NO_m complex of an interstitial nitrogen atom with m oxygen atoms. The number m is estimated as, on the average, m=3 from data on the temperature dependence of the equilibrium constant for the complex formation reaction     

Electrical properties of metal-piezoelectric semiconductor interface under stress

The effects of the mechanical stress on the current-voltage characteristics of metal-piezoelectric semiconductor interface are investigated for both AuCdS and AuGaP Schottky diodes. The changes in currents due to the approximately uniaxial stress, which is applied by bending the crystal wafers attached to the cantilever, are measured. Under the compressive stress parallel to the interface, the current of the diode fabricated on the (0001)Cd or that on the $\text{(}\text{1}\text{?}\text{1}\text{?}\text{1}\text{?}\text{)P}$ surface increases but that of the diode on the $\text{(000}\text{1}\text{?}\text{)S}$ or on the (111)Ga surface decreases. The direction of the changes in current is opposite under the tensile stress. The relative current change $\text{ΔI}\text{I}{}_0$ is proportional to the applied stress and its magnitude at the surface strain 3 × 10^?4is 2.4 × 10^?2, 8.0 × 10^?2, 1.0 × 10^?2 and $\text{0.5 × 10}{}^{\mathrm{?2}}\text{for diodes made on (0001)Cd, (000}\text{1}\text{?}\text{)S, (111)Ga}$ and $\text{(}\text{1}\text{?}\text{1}\text{?}\text{1}\text{?}\text{)P}$ surfaces respectively. These values are also nearly constant over the small bias region in which I₀ is proportional to exp($\text{eV}{}_{\mathrm{a}}\text{KT}$). In this region, the changes in current are transformed to the changes in barrier height. In order to explain this effect, the changes in barrier height are calculated according to the piezoelectricity in the depletion layer of the Schottky diodes. The predicted value agrees with the one obtained experimentally.     

Electrical properties of p-type GaP schottky barrier under stress

The effect of stress on a Schottky barrier height at a metal-semiconductor interface is investigated for metal-p-type GaP contacts. The diodes are fabricated by evaporating metals (Ag, Au) on polar (111)Ga and (1&#x0304;1&#x0304;1&#x0304;)P surfaces. Stress is applied to the diodes by bending the crystal wafers attached to the cantilever. The variation of the barrier height with stress is determined from the measurements of the current-voltage characteristics under stress. The barrier height decreases under compressive stress parallel to the interface and increases under tensile stress. The change in barrier height on the (111)Ga surface is greater than that on the (1&#x0304;1&#x0304;1&#x0304;)P surface. These experimental results are discussed from the point of both the piezoelectricity and the change in band gap caused by stress.     

Generation of thermal donors in silicon: Effect of self-interstitials

The generation of low-temperature thermal donors (TD) in silicon is sensitive to the sample cooling rate (from the anneal to room temperature) and the ambient (air or vacuum). This effect is most clearly pronounced in the case of annealing at 500°C, is noticeable at 480°C, and is practically undetectable at 450°C. The results are interpreted satisfactorily as being due to the TD generation becoming enhanced in the presence of silicon self-interstitial (Si_I) atoms. These atoms are emitted by thermal donors, to be subsequently absorbed by sinks, particularly the sample surface and grown-in microdefects (vacancy voids). When annealing in a vacuum, the surface acts as the main sink. If the anneal is done in air, this sink is passivated as a result of oxidation and/or contamination, with voids becoming the main sinks; as a result, the concentration of Si_I atoms increases substantially and the generation rate is enhanced. Rapid cooling brings about a partial passivation of the voids (as a result of their becoming decorated by rapidly diffusing impurities) and an additional enhancement of the generation rate. The calculated rate curves obtained within this model are well fitted to the experiment.     

Electrical properties of indium implanted silicon

Electrical conductivity and Hall effect were measured from 100° to 278°K as a function of layer removal to determine the indium ionization energy and the presence of compensating centers resulting from the implantation of indium into silicon. The implants were fully annealed to reduce the influence of radiation damage. For comparison, similar measurements were performed on silicon shallow diffused with indium. Differential analysis methods were used to compute carrier concentration, mobility, and resistivity for the stripped layers. In addition, Hall measurements were performed on silicon uniformly doped with indium. In all three cases an indium energy level of 160 meV was observed. Mobility plots versus temperature were also consistent. However, significant compensation effects were noticed in the implants.     

Electrical properties of surface functionalized silicon nanoparticles

The present study relates to the applicability of silicon nanoparticles as basic component in printing inks for the fabrication of printable electronic devices. It is systematically investigated, how the surface functionalization of silicon nanoparticles with 1-alkenes affects the electrical properties of thin films made of them. Therefore, films of as-prepared silicon nanoparticles with a size of 42 nm as well as freshly etched ones, both terminated with hydrogen, are compared with films of silicon nanoparticles functionalized with n-octene, n-dodecene, allylmercaptan, and allylamine, respectively. It is found, that the activation energy of the electron transport through the films is in the range of 0.5 eV and scales with the polarity of the functionalization.     

Electrical properties of plastically deformed silicon crystals

The influence of the nature of the interaction of deformation and impurity defects on the scattering of majority carriers is investigated in silicon single crystals. Fiz. Tverd. Tela (St. Petersburg) 40, 1816–1817 (October 1998)     

Electrical activation of boron-implanted silicon during rapid thermal annealing

The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B⁺ fluences ranging between 5×10¹⁴ and 1×10¹⁶cm⁻² and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT<1000°C and cannot be completed in times typical of rapid thermal annealing (a few tens of seconds). The analysis of carrier profiles indicates that the time constant for activation is strongly affected by local damage and dopant concentration. If the total boron concentration exceeds equilibrium solubility, precipitation occurs concomitant to activation, even if the substitutional boron fraction is still lower than equilibrium solubility. ForT≧1000°C complete activation is obtained in times of about 10 s. In the case of preamorphized Si the activation occurs very quickly, during the recrystallization of the amorphous layer, for all the examined temperatures.     

Phosphorus-doped silicon under uniaxial tensile strain investigated by PAC

Half-metallic diluted antiferromagnetic semiconductors (HM-AF-DMSs) are magnetic materials that are half-metallic and yet do not exhibit magnetization. The remarkable features of these materials and the possible experimental verifications for determining whether or not a material is a HM-AF-DMS by the detection of hyperfine interactions are discussed on the basis of the first-principles calculations of the electronic structure.     

Electrical properties of thin PECVD silicon oxynitride films

Thin silicon oxynitride films with excellent uniformity were prepared by plasma enhanced CVD. Oxygen incorporation leads to improved breakdown behavior and to reduction of the film conductivity compared to PECVD silicon nitride layers. Thin PECVD silicon oxynitride films deposited on single crystal and poly-Si exhibit good insulation properties in both cases.     

Hole structure of gray tin under tensile stress

The energy band structure for holes in gray tin under uniaxial tensile stress is discussed. It is shown that there is a region in the Brillouin Zone where the hole effective mass along the stress direction becomes negative. The structure of the constant energy surfaces is studied, and the number of holes contained in the energy surface is shown to obey a E³ law for small energy E.     

Copper donors in silicon

The temperature dependences of the resistivity and of the Hall constant were measured for dislocation-free p-type silicon saturated with copper under different conditions at temperatures round 1000°C. The analysis of the results and their discussion led to the conclusion that the copper donors form complexes the dimension and physical characteristics of which depend on the way the sample is prepared.