Nikolai Yarykin

Transformation of deep-level spectrum of irradiated silicon due to hydrogenation under wet chemical etching

The effect of wet chemical etching in acid solutions on the energy spectrum of n- and p-type silicon crystals previously irradiated with high-energy electrons is studied by deep-level transient spectroscopy. It is observed that together with the well known radiation defects a number of novel deep-level centres appear near the etched surface. The depth profiles of the deep-level centres are investigated depending on the irradiation dose and the temperature of subsequent annealing. The novel centres observed are shown to be complexes of radiation defects with the hydrogen atoms which penetrated into the crystal during etching. The origin of some of these centres from the particular vacancy-related defects is established. A simple quantitative description is given of hydrogen atom penetration during the etching and formation of the hydrogen - radiation defect complexes. Based on this analysis, the radius of hydrogen capture to the well known A-centre (vacancy - oxygen complex) is estimated and the centre with an energy level of eV is identified as a complex of the A-centre with two hydrogen atoms.

Similarities in the electrical properties of transition metal-hydrogen complexes in silicon

We review our recent studies on the reactions of hydrogen with transition-metals (Pd, Pt, Ag, and Au) in crystalline Si. Hydrogen was incorporated into the samples by wet-chemical etching. Deep-level transient spectroscopy (DLTS) on Schottky diodes reveals several transition metal‐hydrogen complexes in n- and p-type samples. From DLTS profiling, we are able to estimate the number i of hydrogen atoms in the TM‐Hi complexes. All complexes with i 1, 2 are electrically active. Striking similarities are found for isoelectronic complexes, e.g. Pt‐H2 and Au‐H1. Transition metal complexes with more than three hydrogen atoms are likely to be electrically passive. All hydrogen related complexes disappear after heat treatments above 600 K for several hours.

Simulation of hydrogen penetration into p-type silicon under wet chemical etching

Penetration of hydrogen into p-Si and formation of hydrogen-containing defects under wet chemical etching were simulated. The simulated concentration profiles of hydrogen-containing defects were compared to the measured profiles. It is shown that the hydrogen-distribution relaxation after termination of etching is important in the crystals with a low trap concentration. Consideration of such relaxation makes it possible to describe all experimental profiles without assuming that the hydrogen diffusivity is anomalously high. However, the experimental profiles can also be described assuming that the hydrogen diffusivity is high, with the effect of relaxation being less important in this case. It is shown that a comparative analysis of concentration profiles for the hydrogen-containing centers makes it possible to determine the number of hydrogen atoms in these centers in the cases where these profiles are either formed mainly in the course of etching or are modified significantly by transient hydrogen diffusion.

Annealing kinetics of boron-containing centers in electron-irradiated silicon

The annealing kinetics of BiOi pairs created by fast-electron irradiation in Si wafers is studied. The wafers are grown by the Czochralski method and doped with boron to different levels. It is found that, at a particular temperature, the annealing rate steadily increases with increasing boron concentration. The results are described with a simple model that takes into consideration the interaction of interstitial boron atoms with oxygen atoms and substitutional boron atoms. In the context of the model, the temperature dependence of the dissociation rate of the BiOi complex is calculated.

Impact of thermal annealing on deep-level defects in strained-Si∕SiGe heterostructure

Si∕Si1−xGex∕Si heterostructures consisting of relaxed SiGe layers of graded and constant (x=0.2) composition with a strained-Si layer on top have been studied by the capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS), and electron-beam induced current (EBIC) techniques. Analysis of the C-V and EBIC data shows that electrically active defects are introduced during growth into both the graded and constant-composition SiGe layers in a high concentration (∼1016cm−3). The defects are attributed to dislocation trails, i.e., the quasi-two-dimensional extended defects formed behind gliding threading dislocations. Electrical activity of the dislocation trails is reduced following the annealing at 800°C. The DLTS measurements reveal a much lower density of deep-level defects which are mainly located in the graded SiGe layer. The 800°C annealing also gives rise to an additional DLTS peak. The deep-level centers corresponding to this peak are located close to the strained-Si∕SiGe interface and can be...

New Results on the Electrical Activity of 3d-Transition Metal Impurities in Silicon

In silicon several electronic levels are known which can be attributed to transition metals. Ignorance persists however about the specific nature of the defect centers. Some progress was made recently on identifying electronic levels from substitutional or interstitial lattice sites and on identifying levels from defect complexes. The sensitive Laplace DLTS technique allows us to determine depth profiles or the influence of the electrical field on the emission rate with unparalleled accuracy. Three examples will be discussed in this short review: The identification of the CoB pair, a reinterpretation of the Ti DLTS spectrum and the complex formation of interstitial Cu with substitutional Cu as the nucleation site.

New hydrogen-related radiation-induced deep-level center in boron-doped silicon

Abstract The interaction of hydrogen impurity with radiation defects in silicon is studied by DLTS. Prior to the electron irradiation at room temperature, hydrogen was introduced into the p-type samples by wet chemical etching. Two new deep-level centers are detected only in float-zone crystals. The depth profiles of the new centers resemble those of the boron–hydrogen pairs. One center reveals a charge-driven bistability; the deep levels corresponding to both of its configurations as well as transformation kinetics are determined. Our results indicate that the bistable defect is interstitial in nature and includes boron and hydrogen.

Evidence for room-temperature in-diffusion of nickel into silicon

Interstitial nickel in crystalline Si is shown to be a fast diffuser at room temperature. In this study, Ni is incorporated in Si by wet chemical etching in nickel-contaminated alkaline solutions. Nickel in-diffusion is observed by means of detecting the electrically active NiVO defect, which is formed due to Ni capture to the vacancy–oxygen complex in electron-irradiated Si. The depth profiles of the NiVO concentration measured by the deep-level transient spectroscopy technique extend to ∼15 μm in the samples doped with Ni at 35 °C for 30 min. This allows us to get a lower estimate for the nickel diffusivity at this temperature as 10−9 cm2/s. The activation energy for electron emission from the NiVO level and the apparent capture cross section are equal to 371 meV and 3 × 10−15 cm2, respectively. The NiVO complex dissociates at 300 °C reestablishing the initial concentration of the VO centers.

Low temperature hydrogenation of dislocated Si

The effect of wet chemical etching and subsequent annealing on the electrical activity of the dislocation-related centers in n-type Si is investigated by the deep-level transient spectroscopy. It is observed that hydrogen penetrates into the samples already during room temperature etching but passivates the dislocation centers only after 300°C annealing. The different dislocation centers exhibit different efficiency of hydrogen passivation. Possible reasons for the observed peculiarities of the dislocation passivation are discussed.

Effect of irradiation in sem on electrical properties of silicon

The defect formation in gold doped n-Si under the irradiation by electrons with the subthreshold energy or light illumination have been studied by the deep level transient spectroscopy (DLTS) technique. The formation of three at least new electrically active defects was observed. It has been shown that Ec-0.20 energy level is associated with hydrogen-gold complex. Both the treatments used were found to stimulate hydrogen transport in silicon.