Peculiarities of the thermal donor formation in Czochralski grown silicon under high hydrostatic pressure

Oxygen agglomeration processes leading to the formation of thermal donors in Czochralski grown silicon subjected to heat treatment at T=450°C at atmospheric pressure and a high hydrostatic pressure of P=1 GPa are studied. The samples investigated were doped with isoelectronic impurities of carbon and germanium. Both impurities are known to suppress the formation processes of thermal donors under normal conditions of heat treatment. It has been shown that the stress applied during heat treatment to Cz-Si with high concentrations of these impurities results in an enhanced formation of thermal donors. This effect is thought to be associated with increasing oxygen diffusivity under stress. © 2001 SPIE

Early stages of oxygen aggregation and thermal donors in silicon annealed under hydrostatic pressure

Thermal donor formation in Czochralski-grown silicon heat treated at T = 450°C under hydrostatic pressure is investigated by means of optical and electrical measurements. It has been shown that oxygen agglomeration processes in stressed Cz-Si lead to an enhanced formation of the well-known thermal double donors. This effect is believed to be due to increasing oxygen diffusivity under stress. Some important differences between the formation processes in Cz-Si annealed under normal conditions and high hydrostatic pressure are discussed

"New donors" in Czochralski grown silicon annealed at T≥ 600°C under compressive stress

Effects of compressive stress on oxygen agglomeration processes in Czochralski grown silicon heat treated at T = 450°C, used as a reference temperature, and T = 600°C to 800°C are investigated in some detail. Compressive stresses of about P = 1 GPa lead to enhanced formation of Thermal Double Donors in materials annealed over a temperature range of T = 450°C - 600°C. It has been shown that the formation of thermal donors at T = 450°C under normal conditions and compressive stress is accompanied with loss of substitutional boron. In contrast, the concentration of the shallow acceptor states of substitutional boron in silicon annealed under stress at T≥ 600°C remains constant. An enhancement effect of thermal donor formation is gradually weakened at T≥ 700°C. The oxygen diffusivity sensitive to mechanical stress is believed to be responsible for the observed effects in heat-treated silicon

Oxygen agglomeration and formation of oxygen-related thermal donors in heat-treated silicon

The characteristic features of production processes of thermal donors in Czochralski grown silicon heat treated at T=450°C under hydrostatic pressures of about 1 GPa are studied. Two families of oxygen-related donors are formed under compressive stress. The first one is the well-known thermal double donors whose production rate is increased by a factor of five as compared with that observed at atmospheric pressure. Along with them, new thermal donors with similar energy states are also produced. This family was found to be a dominant contributor to the thermal donors formed under compressive stress. The features of formation processes of both kinds of thermal donors are briefly discussed

Double thermal donors in Czochralski-grown silicon heat-treated under atmospheric and high hydrostatic pressures

The formation kinetics of Thermal Double Donors, a dominant family of thermal donors in Czochralskigrown silicon annealed at T < 600 °C, is studied in detail. A striking enhancement effect of hydrostatic pressures of about 1 GPa on their formation processes, even in a temperature region of thermal instability of these donor centers at about T = 600 °C under normal conditions, is clearly demonstrated. The experimental data obtained in the present work are in agreement with the recent theoretical calculations of oxygen diffusion and agglomeration processes in heat-treated Si

Radiation-induced defects in czochralski-grown silicon containing carbon and germanium

Formation processes of vacancy-oxygen (VO) and carbon interstitial-oxygen interstitial (CiOi) complexes in electron-irradiated Czochralski-grown Si crystals (Cz-Si), also doped with Ge, are investigated. IR spectroscopy measurements are employed to monitor the production of these defects. In Cz-Si with carbon concentrations [Cs] up to 1 × 1017 cm-3 and Ge concentrations [Ge] up to 1 × 1020 cm-3 the production rate of VO defects as well as the rate of oxygen loss show a slight growth of about 10% with the increasing Ge concentration. At high concentrations of carbon [Cs] around 2 × 1017 cm-3 the production rate of VO defects is getting larger by ∼40% in Cz-Si:Ge at Ge concentrations around 1 × 10 19 cm-3 and then at [Ge] ≈ 2 × 1020 cm-3 this enlargement drops to ∼13%, thus approaching the values characteristic of lesser concentrations of carbon. A similar behavior against Ge concentration displays the production rate of CiOi complexes. The same trend is also observed for the rate of carbon loss, whereas the trend for the rate of oxygen loss is opposite. The behavior of Ge atoms is different at low and high concentrations of this isoelectronic impurity in Cz-Si. At low concentrations most isolated Ge atoms serve as temporary traps for vacancies preventing them from indirect annihilation with self-interstitials. At high concentrations Ge atoms are prone to form clusters. The latter ones are traps for vacancies and self-interstitials due to the strain fields, increasing the importance of indirect annihilation of intrinsic point defects. Such a model allows one to give a plausible explanation for the obtained results. A new band at 994 cm-1 seen only in irradiated Ge-doped Cz-Si is also studied. Interestingly, its annealing behavior was found to be very similar to that of VO complexes. © 2009 IOP Publishing Ltd

Carbon, oxygen and intrinsic defect interactions in germanium-doped silicon

Production and annealing of oxygen-vacancy (VO) and oxygen-carbon (C iOi, CiOiI) defects in germanium-doped Czochralski-grown silicon (Cz-Si) containing carbon are investigated. All the samples were irradiated with 2 MeV fast electrons. Radiation-produced defects are studied using infrared spectroscopy by monitoring the relevant bands in optical spectra. For the VO defects, it is established that the doping with Ge affects the thermal stability of VO (830 cm -1) defects as well as their fraction converted to VO2 (888 cm-1) defects. In Ge-free samples containing carbon, it was found that carbon impurity atoms do not affect the thermal stability of VO defects, although they affect the fraction of VO defects that is converted to VO2 complexes. Considering the oxygen-carbon complexes, it is established that the annealing of the 862 cm-1 band associated with the CiOi defects is accompanied with the emergence of the 1048 cm-1 band, which has earlier been assigned to the C sO2i center. The evolution of the CiO iI bands is also traced. Ge doping does not seem to affect the thermal stability of the CiOi and CiO iI defects. Density functional theory (DFT) calculations provide insights into the stability of the defect clusters (VO, CiO i, CiOiI) at an atomic level. Both experimental and theoretical results are consistent with the viewpoint that Ge affects the stability of the VO but does not influence the stability of the oxygen-carbon clusters. DFT calculations demonstrate that C attracts both Oi and VO pairs predominately forming next nearest neighbor clusters in contrast to Ge where the interactions with Oi and VO are more energetically favorable at nearest neighbor configurations. © 2011 IOP Publishing Ltd