A dominant electrical defect in GaAs

Several as-grown Bridgman and Czochralski GaAs crystals, with dominant electrical levels from 0.13–0.20 eV below the conduction band, have been studied by the temperature-dependent Hall-effect, spark-source mass spectroscopy, and secondary-ion mass spectroscopy. It is shown that no impurity is of a sufficient concentration to account for these levels, and therefore they are composed of single or multiple defects. The detailed nature of the defects has not yet been established but may involve an As vacancy. It is believed that this is the first time that a dominant electrically active center has been shown to be a pure defect in any as-grown semiconductor.     

An orientation-dependent defect in ion-implanted silicon

A new EPR spectrum is resolved in the N⁺-implanted silicon, and this center can be produced only by the 〈110〉 channeling ions in the region underneath the amorphous layer.     

Radiation defect clusters in electron-irradiated silicon

Radiation defect formation in Czochralski-grown (pulled) and vacuum float-zone n-Si (ρ=15 to 150 ωcm) irradiated by electrons with energy E_e=2.5 to 1200 MeV has been studied. The results have been obtained from an analysis of the dose, energy and temperature dependences of the concentration n, Hall mobility μ _n , and charge-carrier lifetime τ. The experimentally observed peculiarities in the variation of n, μ _n , and τ irradiation by electrons with E10 MeV have been explained taking into account the formation of radiation defect clusters in the bulk of the crystal induced by such electrons. The correlation coefficients K_i have bsen obtained which take into consideration the “evolution” of primary displacement cascades in the location of which clusters are formed. The parameters of radiation defect clusters produced by electrons of different energies have been calculated using these coefficients.     

A copper- and boron-related defect in silicon

The resistivity of boron-doped silicon can be significantly increased by polishing such material with an appropriate amine- and copper-containing slurry. This effect is ascribed to a passivation of the boron acceptors by a defect produced or introduced by the polishing process. Three new, so far unknown localized vibrational modes at 691, 720, and 1038 cm^–1 are observed in highly boron-doped silicon samples after such a polishing treatment. Two of these localized modes can be identified as due to a boron-containing defect. High concentrations of copper found in the samples after appropriate polishing indicate a participation — either directly or indirectly — of this metal in the passivation process.     

A fourfold coordinated point defect in silicon

Vacancies, interstitials, and Frenkel pairs are considered to be the basic point defects in silicon. We challenge this point of view by presenting density functional calculations that show that there is a stable point defect in silicon that has fourfold coordination and is lower in energy than the traditional defects.     

氮对金刚石缺陷发光的影响

利用低温显微荧光光谱研究了IIa型、Ib型、Ia型金刚石的缺陷发光性质. 研究发现, 随着氮含量增加, 间隙原子及空位逐渐被氮原子所束缚, 从而使得GR1中心、533.5 nm及580 nm中心等本征缺陷发光减弱, 而氮-空位复合缺陷(NV中心)及523.7 nm中心等氮相关缺陷发光增强. 高温退火后, 间隙原子与空位可以自由移动, IIa型金刚石中出现了NV⁰中心, Ib型金刚石中只剩下了NV中心, Ia型金刚石中氮原子之间发生团聚, 出现了H3中心及N3中心. 另外, 氮作为施主原子, 有利于负电荷缺陷的形成, 如3H 中心、NV^- 中心.     

Thermally induced defect photoluminescence in hydrogenated amorphous silicon

The intrinsic defect photoluminescence of hydrogenated amorphous silicon (a-Si:H) films has been investigated at high intensities of optical pumping that lead to heating of the film. It has been revealed that, for short heating times, the intensity of the defect photoluminescence increases exponentially with an increase in the temperature with an activation energy of 0.85 eV, which is considerably higher than the activation energy (∼0.2 eV) determined from experiments on classical annealing. This and other experimental results on the temperature dependence of the intensity and kinetics of the defect photoluminescence have been explained in terms of the “hydrogen glass” model by thermally induced generation of intrinsic defects in amorphous silicon. The results of the calculations are in good agreement with the experimental data on the defect photoluminescence that reflects the formation and annihilation of defects for short heating times under optical excitation.     

Interaction of nitrogen dioxide molecules with the surface of silicon nanocrystals in porous silicon layers

The methods of infrared absorption spectroscopy and electron paramagnetic resonance are used for studying the effect of adsorption of NO₂ molecules, which are strong acceptors of electrons, on the electronic and optical properties of silicon nanocrystals in mesoporous silicon layers. It is found that the concentration of free charge carriers (holes) in silicon nanocrystals, which exhibits a nonmonotonic dependence on the NO₂ pressure, sharply increases in the presence of these molecules. At the same time, a monotonic increase in the concentration of dangling silicon bonds (P_b1 centers) is observed. A microscopic model proposed for explaining this effect presumes the formation of donor-acceptor pairs P ₊ ^b1 -(NO₂)^? on the surface of nanocrystals, which ensure an increase in the hole concentration in nanocrystals, as well as P_b1 centers, which are hole-trapping centers. The proposed model successfully explains a substantial increase in photoconductivity (by two or three orders of magnitude) in the layers of porous silicon in the presence of NO₂ molecules; the increment in the concentration of free charge carriers is detected within an order of magnitude of this quantity. The results can be used in designing electronic and luminescence devices based on silicon nanocrystals.     

Ab initio identification of the nitrogen diffusion mechanism in silicon

In this Letter, we present ab initio results identifying a new diffusion path for the nitrogen pair complex in silicon, resulting in an effective diffusivity of 67exp((-2.38 eV/kT) cm2/s. This nudged elastic band result is compared with other nitrogen diffusion paths and mechanisms, and is determined to have unmatched agreement with experimental results. It is also shown that careful consideration of total energy corrections and use of a fully temperature-dependent diffusion prefactor have modest but important effects on the calculation of diffusivity for paired and for interstitial nitrogen.     

Extended defect removal in silicon by rapid thermal annealing

Summary Germanium, arsenic and krypton ions of 600 keV energy were implanted in <100> silicon substrate at 250°C. The hot implantation results in the formation of extended defects (dislocation loops and cluster of point defects) as residual damage. Rapid thermal annealing process at a temperature above 1000°C was used to remove the damage. Rutherford-backscattering channelling technique was used to measure the amount of defects and their annealing. In some cases the channelling results were correlated to transmission electron microscopy (TEM) analysis. The annealing process of the damage is governed by an activation energy of (4.4±0.2) eV for both germanium and arsenic implants. During RTA processes broadening of the As and Ge distributions is quite negligible. The Kr atoms interact instead with defects and the annealing even after a prolonged time at 1100°C is not complete, bubbles surrounded by extended defects are left The authors of this paper have agreed to not receive the proofs for correction.