A. Shalimov

Strain nonuniformity in GaAs heteroepitaxial films on Si(001) studied by x-ray diffraction

High-resolution x-ray diffraction measurements are used to fully characterize the strain state of relaxed highly mismatched GaAs films, grown on vicinal Si (001) substrates by molecular beam epitaxy. The nonuniformity of the misfit dislocation network at the GaAs∕Si (001) interface is studied by analyzing the profiles of x-ray diffraction peaks and the reciprocal space maps for different reflections. The detailed analysis of the peak positions shows a dependence of the relaxation on the crystallographic direction, with the relaxation being larger in the direction perpendicular to the α-dislocation lines. Based on analytical expressions for the full width at half maximum in the longitudinal and transverse sections, an advanced version of the Williamson-Hall plot [Acta Metall. 1, 22 (1953)] is proposed that takes into account the geometry of dislocation distribution and the scattering geometry. We show that this type of analysis can reveal both the type and density of misfit dislocations. The measured peak ...

Asymptotic x-ray scattering from highly mismatched epitaxial films

We study x-ray diffraction peak profiles from highly mismatched relaxed epitaxial films at momentum transfers exceeding the peak widths. Calculated profiles for misfit dislocations are compared with triple-crystal diffraction profiles from GaAs/Si(001) epitaxial films. We find that the longitudinal and transverse scans have a common q−4 asymptote but approach it differently, so that their profiles are qualitatively different in the experimentally available momentum range. The possible contribution from threading dislocations is estimated.

X-ray diffraction peaks at glancing incidence and glancing exit from highly mismatched epitaxial layers

We find that the widths of double-crystal x-ray diffraction peaks in asymmetric reflections of relaxed GaAs∕Si(001) heteroepitaxial layers in reciprocal diffraction geometries (glancing incidence and glancing exit) are notably different. This observation is in agreement with previous measurements on other heteroepitaxial systems but apparently contradicts the reciprocity principle of electrodynamics. We show that the apparent contradiction originates from the summation of the scattered waves that are collected by the detector in a double-crystal setup and resolve it by giving an appropriate description of the peak widths.

Effect of high temperature?pressure on nitrogen-doped Czochralski silicon

The effects of enhanced hydrostatic pressure (HP, up to 1.2 GPa) on the properties of nitrogen-containing Cz-Si:N (N content , interstitial oxygen concentration 9 × 1017 cm−3) and of Czochralski-grown silicon (Cz-Si, reference samples) treated for 5 h at 1070–1570 K–HP have been investigated by photoluminescence, x-ray and infrared absorption methods. HP acts on Cz-Si:N and on Cz-Si in a similar way: oxygen precipitation and creation of numerous cluster-like and extended defects are stimulated, especially at 1230–1400 K. The small cluster-like oxygen-related defects are, however, more numerous in HP treated Cz-Si:N while the extended ones (dislocations) are created at 1230 K in a lowered concentration. A qualitative explanation of the observed effects has been proposed.

Influence of high pressure and temperature on defect structure of silicon crystals implanted with N or Si ions

Abstract (111) oriented Fz-Si crystals were implanted with N + or Si + at 150 keV energy to a dose of 2×10 16 cm −2 . After implantation the samples were treated at a high temperature (up to 1400 K) under hydrostatic argon pressure (up to 1.1 GPa) for 1–5 h. Structural properties of Si:N and Si:Si before and after the treatment were investigated by high-resolution X-ray diffraction, synchrotron topography, transmission electron microscopy and photoluminescence methods. The structural properties of Si:N and Si:Si treated under hydrostatic pressure at 1270 K are different. A buried layer of uniform thickness with smooth interface was formed in Si:N under HP=1.1 GPa; the buried layer/Si interface becomes less smooth with rising treatment time. The shape of interference fringes and their changing distance at rocking curves are explained as an effect of nitrogen diffusion to the buried layer during the treatment. For the treated Si:Si samples, the observed strain changes are related to the out-diffusion of interstitial silicon atoms from the implanted layer to the sample surface and to creation of numerous extended defects near the implanted atoms range. Prolonged treatment (for 5 h) at 1.1 GPa and 1400 K results in creation of dislocations for Si:N while for Si:Si samples the structure of treated samples is more complex, involving also creation of amorphous-like surface film.

Pressure-induced defect structure changes in thin AlGaAs layers

Abstract A study of the defect structure of Al x Ga 1− x As/GaAs layers with varied primary strain state prepared by LPE method and subsequently annealed under high uniform pressure is reported. An influence of high hydrostatic pressure–high temperature (1.2 GPa and 920 K or 1070 K applied for 1 h) on the strain state and defect structure of the layers was investigated by high-resolution X-ray diffractometry and topography (the latter done at the ID19 beamline, ESRF). A treatment-induced change of defect structure was detected for all samples, being more pronounced for the case of treatment at 1070 K. The appearance of treatment-induced stresses at the precipitate/matrix boundary caused the creation of new defects and resulted in an increase of rocking curve width and in enhancement of the diffuse scattering intensity.

Structure of Magnetically Ordered Si:Mn

The structure studies of single crystalline silicon implanted at 340 K or 610 K with Mn+ ions (Si:Mn) and subsequently processed under atmospheric and enhanced hydrostatic pressure at up to 1270 K are reported. The defect structure was determined by an analysis of X-ray diffuse scattering around the 004 reciprocal lattice point and by electron microscopy. High resolution X-ray diffraction techniques based on the conventional source of radiation were used for this purpose. The crystal structure of Si:Mn and the Si1-xMnx precipitates in the implantation – disturbed layer were studied by synchrotron radiation diffraction in the grazing incidence geometry. Processing of Si:Mn results in crystallization of amorphous Si within the buried implantation – disturbed layer and in formation of Mn4Si7 precipitates. Structural changes are dependent both on temperature of the Si substrate at implantation and on processing parameters.

Influence of Neutron Irradiation on Stress - Induced Oxygen Precipitation in Cz-Si

Oxygen precipitation and creation of defects in Czochralski grown silicon with interstitial oxygen concentration 9.4·1017 cm-3, subjected to irradiation with neutrons (5 MeV, dose 1x1017 cm-2) and subsequently treated for 5 h under atmospheric and high hydrostatic pressures (HP, up to 1.1 GPa) at 1270 / 1400 K, were investigated by spectroscopic and X - Ray methods. Point defects created by neutron irradiation stimulate oxygen precipitation and creation of dislocations under HP, especially at 1270 K. The effect of pressure treatment is related to changed concentration and mobility of silicon interstitials and vacancies as well as of the VnOm – type defects.

Effect of High Pressure - Temperature on Structure of Silicon Crystals Implanted with Nitrogen / Silicon

Enhanced pressure (HP) at annealing exerts pronounced effect on the structural properties of Si crystals implanted with N (Si:N) or Si (Si: Si). The structural properties of Si:N and Si:Si treated under HP are different. In the case of Si:N and Si:Si prepared in the similar way, with implanted dose 2 ×10cm and energy 150 keV, a buried nitrogen-containing layer was created in Si:N after the treatment at HP 1270 K for 1 h while dense a rray of dislocations was detected in the reference Si:Si samples. The observed changes of strain in Si:S are related to out-diffusion of interstitial silicon atoms from the damaged areas to the sample surface and to creation of numerous extended defects within the implanted atoms range.

Investigations of the Effect of High Pressure on the Annealing Behavior of Oxygen Related Defects in Silicon

Abstract. Infrared and x-ray studies are reported on the effect of high pressure (HP) treatments on the annealing behavior of oxygen-related defects, particularly the VO defect, formed in neutron-irradiated Cz-Si. Upon annealing at 300 o C, the VO defect begins to convert to the VO 2 defect. The main purpose of this paper is the study of the effect of pressure on the conversion of the VO to the VO 2 defect. To this end, isothermal treatments of 45 min duration at a time, were performed at temperatures T 1 =325 o C and T 2 =350 o C with and without the application of hydrostatic pressure of 10.5 kbar. The analysis of the IR results indicates that the application of pressure enhances the growth of the VO 2 defect and also the growth of the various V n O m complexes, which give rise to satellite bands in the region of the VO band. X-Ray reciprocal space maps and rocking curves received at the end of the annealing sequence reveal the presence of point-like defects, which are more numerous in the stressed samples. These defects could be considered to act as nucleation sites for the oxygen impurity precipitation. Introduction The main oxygen-related defect in irradiated Cz-grown Si is the oxygen-vacancy complex, the well-known A-center the neutral charge state of which gives rise to a LVM band at ~ 828 cm