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Silicon doped with boron is the most widely used material in modern microelectronic devices based on p-Si. Therefore, it is important to thoroughly understand boron's role in the processes of defect-impurity interaction in Si both on growing the material and during operation of devices. In this work, interactions of boron with oxygen in Si are investigated by studying boron absorption intracenter transitions, which are known to be highly sensitive to the local environment. In boron-doped Si, two lines with maxima at 228 and 261.3 cm−1 were detected. The linear dependence of lines intensity on boron concentration and the quadratic on oxygen content testifies that the defect responsible for the lines can be identified as BsO2i. The observed absorption lines correspond to the transitions from the ground to the excited states of boron, which are shifted toward lower frequencies relative to the main transitions due to a deformation perturbation from neighboring oxygen atoms. The activation energy of annealing and ionization energy of defect are determined. The properties of the registered ВsO2i defect differ from the known ВsO2 associated with the light-induced degradation of solar cells by local configuration. The data obtained testify that the ВsO2i defects with different properties can be formed in Si and must be taken into account when developing Si:B-based devices because they can play an important role in charge carrier transfer and affect the electrical and optical parameters of the material. [ABSTRACT FROM AUTHOR]

The lithium donor centers in Si1–xGex (x = 0.0039–0.05) single crystals enriched in spinless 28Si and 72Ge isotopes (99.998 and 99.984%, respectively) are studied by electron spin resonance at temperatures of T = 3.5–30 K and compared with its behavior in Si crystals. It is shown that lithium center with trigonal ([111]) symmetry has a most stable configuration in bulk Si1–xGex for different values of x < 5 at %. Axial symmetry is explained by the distortion of the lithium central position and their neighboring atoms. The spin relaxation rates were studied in temperature range 4–30 K and it was shown that transverse and longitudinal relaxation consist of two components with rates differ by almost an order of magnitude. Together with Raman processes for 1/T1, a decrease in the exponent below T5 is observed. This behavior is explained by cross-relaxation through states of the distorted configuration of lithium, which arise due to modulation of the crystal field potential by random distribution of Ge atoms. [ABSTRACT FROM AUTHOR]

Ramsey oscillations have been observed in germanium doped with shallow impurities exposed to terahertz pulses from the NovoFEL facility involving free-electron lasers in experiments performed using the standard method with the action of a sequence of two optical pulses at the frequency close to the frequency of the 1s(A1) → 2p0 impurity transition. The coherent state of the ensemble of donors has been detected by measuring the photocurrent caused by the thermal ejection of electrons from the 2p0 state to the conduction band. The revealed effect is quite stable under experimental conditions, in particular, to the temperature regime, which allows the further improvement in artificial systems based on shallow donors in germanium. [ABSTRACT FROM AUTHOR]

Single-crystal 70Ge germanium with high isotopic and chemical purity has been prepared by a hydride method. Germanium isotopes have been separated by centrifugation with the use of monogermane as a starting volatile substance. Isotopically enriched polycrystalline 70Ge has been prepared by pyrolyzing 70GeH4 monogermane. A 70Ge single crystal has been grown by the Czochralski technique. The resultant material has p-type conductivity and intrinsic resistivity at room temperature. The concentration of elemental impurities is under 10–6 to 10–5 wt %. The isotopic purity of the 70Ge single crystal is 99.926 at % and it contains a record low concentration of the odd isotope 73Ge: 0.00007 at %. [ABSTRACT FROM AUTHOR]