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The dependencies of concentrations of thermal equilibrium vacancies and interstitials on temperatures in Si crystals are determined directly, which has been a long-standing issue since the 1950s. They are evaluated by combining the formation energies and self-diffusion entropies deduced from the analyses of self-diffusion coefficients, and migration entropies deduced from diffusion coefficients of point defects. The concentrations as the number density of thermal equilibrium vacancies and interstitials at temperature T (K) are determined to be 5 × 1022exp(6.5)exp(–3.85 eV/k B T) and 5 × 1022exp(10.6)exp(–4.3 eV/k B T) cm−3, respectively. The diffusion coefficients of vacancies and interstitials are determined to be 2.7 × 10−3exp(–0.45 eV/k B T) and 2.5 × 10−2 exp(–0.49 eV/k B T) cm2 s−1, respectively. The results are discussed in comparison with those reported experimentally.

First results are presented of a study on the impact of O and Ge doping on {113}-defect formation in Si using in situ 2 MeV e-irradiation in a high voltage electron microscope. Comparison with undoped Si, reveals a suppression of {113}-defect formation due to O and Ge. The observations are discussed in the frame of a theoretical model assuming quasi-chemical reactions to describe the intrinsic point defect behaviour during irradiation as a function of irradiation temperature and specimen thickness. It is shown that for irradiations at high temperatures, intrinsic point defect diffusivity values derived from crystal growth and metal diffusion experiments can be used to explain the observations semi-quantitatively.

Oxygen-containing germanium (Ge) single crystals with low density of grown-in dislocations were grown by the Czochralski (CZ) technique from a Ge melt, both with and without a covering by boron oxide (B(2)O(3)) liquid. Interstitially dissolved oxygen concentrations in the crystals were determined by the absorption peak at 855 cm(-1) in the infrared absorption spectra at room temperature. It was found that oxygen concentration in a Ge crystal grown from melt partially or fully covered with B(2)O(3) liquid was about 10(16) cm(-3) and was almost the same as that in a Ge crystal grown without B(2)O(3). Oxygen concentration in a Ge crystal was enhanced to be greater than 10(17) cm(-3) by growing a crystal from a melt fully covered with B(2)O(3); with the addition of germanium oxide powder, the maximum oxygen concentration achieved was 5.5 x 10(17) cm(-3). The effective segregation coefficients of oxygen in the present Ge crystal growth were roughly estimated to be between 1.0 and 1.4., Article, JOURNAL OF CRYSTAL GROWTH. 312(19):2783-2787 (2010)

Fo rn -type (phosphorus-doped) floating-zone grown silicon samples, a hitherto unreported ESR signal was detected after the samples were doped with iron and irradiated with electrons. Analysis of the hyperfine structure and the angular dependence of the resonance peak positions of the spectrum, labelled TU6, indicated that the signal originates from a defect complex of monoclinic-I symmetry containing single phosphorus and single iron atoms. The spectrum can be described in terms of a paramagnetic system with S = 1/ 2a ndg values greatly deviating from that of a free electron, as well as spin S = 3/ 2a ndg ≈ 2. The spin S = 3/ 2m ay correspond to a positively charged iron atom (3d 7 state) and, thus, to a doubly positive charge state of a TU6 related complex. The fact that the TU6 signal was detected only under strong external illumination for n-type samples also supports this assignment. Results obtained during isochronal annealing of the irradiated samples suggest the possible involvement of a divacancy in the formation of an iron–phosphorus pair in silicon.

We present results of correlative measurements of platinum–hydrogen (Pt–H) complexes in silicon using infrared absorption (IR) and ESR measurements. Relative concentrations of the complexes in the samples were varied employing various gas pressures during hydrogen doping procedure. The ESR and IR results for the PtH 2 and PtH 3 complexes showed good correlation in various samples, supporting the existing identification of the IR peaks. The ESR and IR signals assigned to PtH pair, however, behaved differently. Our results suggest that the IR peak assigned previously to PtH pairs only, contains several unresolved components corresponding to Pt m H ( m ⩾1) defects.

We studied dependence of concentrations of vacancy-oxygen (VO) pairs and divacancies (V2) on the concentrations of phosphorus and oxygen in electron-irradiated Czochralski-grown silicon crystals from the measuremement of optical absorption spectra. Specimens were irradiated with 3 MeV electrons with various doses at room temperature. Their optical absorption spectra were measured at about 7 K. The VO pair concentration was proportional to (dose)m and m depended on the concentrations of phosphorus and oxygen. On the other hand, V2 concentration increased with irradiation-dose at low doses but saturated and decreased at high doses.

We present results of an ESR study of tetra-interstitial agglomerates ( I 4 ) in silicon. The defects were formed upon annealing of electron-irradiated silicon samples pre-doped with hydrogen and reveal two ESR spectra, i.e., the B3 which is related to positive charge state of the defect and the NL51 which is related to the neutral defect in an excitonic triplet state. Temperature dependence of the intensity of the NL51 spectra allowed determining parameters of the excitonic state. From photo-ESR measurements, the energy level of the excitonic state was determined to lie at ∼1.03 eV above the valence band.

The stress-induced-dichroism has been measured for the infrared absorption lines of the interstitial oxygen in silicon crystals (Si–O–Si center), to determine the symmetries of the transition dipoles responsible for the A1g-mode-related lines at 648.2 and 1819.5 cm−1 discovered recently. The experimental procedure to determine the symmetries was similar to that adopted by Stavola (Appl. Phys. Lett. 44 (1984) 514). We have found that the transition dipoles associated with the 648.2- and 1819.5-cm−1 lines are, respectively, perpendicular and parallel to the linear Si–O–Si bond axis, confirming the assumption under which the total energy-levels were obtained by Yamada-kaneta (Physica B 302–303 (2001) 172).

We investigated influence of measurement temperature and microwave power on the isotopic shift in fine structure term of spin Hamiltonian of the NL19 ESR spectra, which was attributed to an iron–vacancy pair defect in silicon. Obtained results can be described by the model implying existence of discrete local electron-vibration states. Microwave power dependencies of the signal and the isotopic shift at temperatures below 8 K suggest active role of local vibrations of the iron atoms in spin-system relaxation.

The rate of the Watkins replacement reaction, in which changes of occupation sites between self-interstitials (I) and substitutional group-III impurities (III(s)) in Si crystals occur, was studied from the measurement of optical absorption intensity due to IH2 (a complex of one I and two H atoms). If the IH2 intensity depends on the species of group-III impurities under the same irradiation dose, the weaker intensity means larger displacement rate. After hydrogenation, specimens were irradiated at room temperature. The IH2 intensity was determined from optical absorption measurement at 7 K. The IH2 intensity depended on the B concentration ([B]), being smaller as [B] became larger. It also depended on the species of group-III dopants.

The electron spin resonance spectra Si-B3 and NL51 were detected in hydrogen-doped float-zone-grown silicon (Si) samples after electron-irradiation and annealing for the first time. Recently, the Si-B3 spectra were attributed to tetra-self-interstitial (I 4 ) agglomerates in positive charge-state, however an origin of the NL51 spectra was not yet established. Results obtained in this study suggest that the NL51 originate from an excitonic state of neutral I 4 agglomerate in Si. Therefore, detection of interstitial agglomerates in Si at early stages of their formation becomes possible.

High-resolution photoinduced transient spectroscopy (HRPITS) has been employed to investigate iron-related point defects produced by electron irradiation in high-resistivity silicon. The measurements revealed 16 traps with activation energies ranging from 14 to 530 meV. From the comparison of results, obtained by the HRPITS and ESR measurements performed on the same samples, a trap positioned at Ev+500 meV was attributed to the iron-vacancy pair (Fei)V and that positioned at EV+530 meV to the vacancy complex with two iron atoms (Fei)2V. The former is found to be stable at 400°C, while the latter anneals out at this temperature similarly to the trap at EV+410 meV related to interstitial iron. As a result of the transformation of the (Fei)2V complex and reactions of the interstitial iron with native defects, new iron-related traps with activation energies of 85, 220 and 380 meV are formed.

We studied the properties of irradiation-induced point defects and thermal equilibrium vacancies in Si by detecting hydrogen interacting with these point defects. First, we show the irradiation temperature dependence of the point defect concentration. We studied the optical absorption spectra of complexes of hydrogen and point defects generated by electron irradiation of hydrogenated Si crystals at low temperatures. The concentrations of complexes of hydrogen with vacancy and Frenkel pairs showed a non-monotonic dependence on irradiation temperature. Hence, a metastable interstitial-vacancy (Frenkel pair) model is not applicable to electronirradiated Si. From the dependences of the intensity ratios of the optical absorption due to complexes of H2 and point defects, we determined the migration energies of self-interstitial and Frenkel pairs relative to that of the vacancy. The energies were similar. Second, we determined the vacancy formation energy in high-purity Si by a new quenching method: specimens were heated in H2 gas at various temperatures followed by quenching in water. The formation energy determined by the above method was 4.0 eV, which agrees well with recent theoretical values.

We investigated platinum (Pt)-related defects in silicon (Si) based on the measurement of their optical absorption and found optical absorption peaks related to Pt clusters. Pt and H were separately doped in FZ–Si by heating at 1000–1300 °C followed by quenching in water. Optical absorption spectra were measured at about 5 K with a Fourier transform infrared spectrometer. In a specimen doped with a higher concentration of H than of Pt, we observed optical absorption peaks due to four types of Pt–H complexes. In specimens with a higher concentration of Pt than of H, peaks were observed in the region from 1300 to 1700 cm−1. Based on the peak shift due to the hydrogen isotope and the dependence on excitation energy and the annealing behavior, these peaks are thought to be due to the electronic transitions of Pt-related defects such as Pt clusters, rather than the local vibrational modes of H. The defect centers which gave rise to optical absorption at about 1301, 1318, 1452, and 1474 cm−1 were IR-active cent...

The peculiarities of formation and annealing, and energy level position of an iron–vacancy (FeV) pair in silicon were investigated using electron-spin resonance (ESR) and photo-ESR methods. The pairs are created in iron-doped float-zone grown silicon samples during electron-irradiation and survive annealing treatment at temperatures of 400–500°C. Results of a photo-ESR study suggest that FeV in silicon is a hole trap with an energy level positioned at about 0.51 eV above the valence band. The complexes of a vacancy and two iron atoms (2FeV) are less stable than the FeV pairs and anneal out at 300–350°C in the same samples.

Experimental determination of the activation energy (EV D) of vacancy-mediated self-diffusion in silicon crystals is a long-standing issue. Kube et al. [1] studied self-diffusion of the multilayer (ML) structure of isotope Si (20 bilayers of 28Si/29Si) and of a sandwiched (SW) structure (natSi/28Si/natSi) at low temperatures (650–950 °C) with measurements by secondary ion mass spectroscopy (SIMS) and neutron reflectivity (NR). The former and the latter specimens were grown by molecular-beam epitaxy (MBE) and by the chemical vapor deposition method (CVD), respectively. Kube et al. [1] analyzed their data of the SW structure together with those of Bracht et al. [2] at high temperatures (855–1378 °C) and reported EV D as well as E I D (the activation energy of interstitialmediated self-diffusion) to be 3.52 and 4.92 eV, respectively. These values were in good agreement with those (3.6 and 4.95 eV) reported by Shimizu et al. [3] from measurements of diffusion with Raman spectroscopy in the ML structure (20 bilayers of 28Si/30Si). Kube et al. [1] considered these values to be those of an intrinsic crystal since the results of the two groups [1,3] agreed well. To solve the inconsistency that EV D was smaller than that (4.08 eV) of Sb diffusion [4], Kube et al. [1] introduced the temperature dependence of the thermodynamic properties of vacancies, such as the energies of formation and migration, and entropies of formation and migration, which were first proposed by Seeger et al. [5]. Our Comment is on the preferential sites of vacancy formation, i.e., the sites where the formation energy is smaller than that in a perfect crystal. Carbon in the specimens of SW and ML and vacancy clusters in the ML structure are such sites. The carbon concentrations in ML and SW are 3×1018 and 5×1017 cm−3, respectively [1]. Kube et al. [1] assumed that only electrically active impurities have an effect on the charged vacancy formation but offered no explanation on the neutral vacancy concentration which was responsible for the self-diffusion in their specimen. By a quenching experiment, however, we determined the vacancy formation energy in the carbon-doped specimen to be 3.2 eV [6,7] (determined to be 3.08 ± 0.15 eV after reanalysis of data obtained from quenching between 1200 and 1360 °C), much smaller than 3.85 eV [8,9] (determined to be 3.85± 0.15 eV after reanalysis of data obtained from quenching between 1200 and 1360 °C) by our quenching experiment using a high-purity crystal. Nelson et al. [10] calculated the binding energies between various impurity atoms and a vacancy. According to them, the binding energy between the carbon and a vacancy was 0.11 eV, and hence the vacancy formation energy was 3.58 eV since the formation energy in a perfect crystal was estimated to be 3.69 eV by their calculation. Other theoretical estimates have shown that an electrically neutral impurity, such as Sn in Si, has a large binding energy with a vacancy [11]. On the other hand, many vacancy clusters have been detected by positron annihilation studies in MBE-grown structures [12]. The binding energy between the vacancy clusters and a vacancy was estimated to be about 3.2 eV [13]. Hence, the vacancy formation energy from vacancy clusters is 3.2 eV. These results suggest that the data obtained at low temperatures may have been greatly influenced by carbon atoms, not by carbon precipitates, and by vacancy clusters. Hence, the interpretation that the activation energy of vacancy-mediated diffusion was intrinsic would seem to be doubtful. An abnormally small preexponential factor of vacancymediated diffusion seems to be easily explained by the above discussion since the concentration of carbon and/or the density of vacancy clusters are probably involved in the preexponential factor. If we assume that the simultaneous analyses of diffusion data made by Kube et al. [1] and by Shimizu et al. [3] are appropriate, the difference in the preexponential factors between 0.0011 of Kube et al. [1] and 0.0023 of Shimizu et al. [3] can be attributed to the difference in the density of preferential vacancy sites. Incidentally, if the above view that the low-temperature data were influenced by carbon and/or vacancy clusters is correct, there is no reason to analyze the data at high temperatures and low temperatures simultaneously. Plotting numerical data of Kube et al. [1] and those of Bracht et al. [2] (self-interstitial) and Shimizu et al. [3] in larger magnification than Fig. 4 in Ref. [1], we noticed that the relations between log D and 1/T of all data were approximately linear. We attempt to analyze those data, even though it may be beyond the readers’ situation. Figure 1 shows an example. Solid circles correspond to the data of SW. Probably the size of circles should be larger than this plot if we take the experimental error into consideration. The solid line and the broken line correspond to the fitting lines due to the least-squares fit of the data of SW and Eq. (7) in Ref. [1], respectively. In Fig. 2, data of SW and Shimizu et al. [3] are plotted together with the least-squares fitting lines of the solid and broken lines, respectively. Both data agree well. However, as shown by the solid and broken lines, activation energies are slightly different. It is not easy to understand relations among various data from Fig. 4 in Ref. [1]. Hence, in Fig. 3 we show the fitting lines without data points of various data. Solid and open circles correspond to the data at the highest

Properties of interstitial chromium (Cri) in hydogenated p-type Si crystals were studied by means of an EPR method. Specimens were prepared from a floating-zone grown p-type Si crystal. They were doped with Cr by high temperature annealing in Cr vapor, followed by quenching. Then, they were doped with hydrogen (H) by annealing in H2 gas followed by quenching. We measured their EPR spectra to determine the concentrations of Cri and CrB pair. The intensity of EPR spectrum due to Cri in hydrogenated Si was about one-tenth of that without H when they were doped at 1250°C. The heat of the solution of Cr in hydrogenated Si was determined to be about 1.9 eV which is much smaller than that (2.9 eV) without H doping. The migration energy of Cri in H-doped Si was determined to be 0.70±0.09 eV, which is smaller than that (about 1 eV) without H. Site change from interstitial to substitutional was observed in the specimen co-doped with Cr and Cu.

We studied complexes generated by electron-irradiation of CZ-Si crystals pre-doped with hydrogen (H) from the measurements of optical absorption spectra. Specimens were prepared from a non-doped CZ-Si crystal. They were doped with H by heating at 1300°C in H 2 gas. They were then irradiated with 3-MeV electrons at room temperature. We measured their optical absorption spectra by an FT-IR spectrometer at about 7 K. An 836-cm −1 peak which is due to a V–O pair was very strong. Optical absorption peaks due to complexes of H and self-interstitial (I) such as IH 2 (1987-cm −1 peak), I 2 H 2 (1870-cm −1 peak) and I 3 H 2 (1959-cm −1 peak) were stronger than those of FZ-Si. Due to isochronal annealing, the intensity of V–O pair decreases at above 100°C. Simutaneously with this decrease, two new peaks appeared at about 2126 and 2151 cm −1 . This is due to a formation of VOH 2 complex by a reaction between a V–O pair and a H 2 .

We studied optical absorption spectra of platinum (Pt)-doped Si and found new optical absorption peaks related to Pt. FZ-Si was separately doped with Pt and H by heating at 1300°C followed by quenching in water. Optical absorption spectra were measured at about 7 K with a Fourier transform infrared spectrometer. We observed a new peak at 1719.4 cm −1 in as-quenched specimens and also new peaks in the region from 1300 to 1500 cm −1 after annealing at above 500°C. From the isotope shift caused by deuterium doping, the dependence on excitation energy and the annealing behaviors, these peaks were found to be due to the electronic transition of Pt-related defects such as Pt clusters, rather than to the local vibrational modes of H.

By applying a new quenching method, we determined the formation energy of vacancies (V) in high-purity silicon. Specimens were sealed in quartz capsules together with H2 gas and heated at high temperatures for 1 h followed by quenching in water. By this method, V are quenched in the form of complexes with hydrogen and the formation energy of V can be determined from the quenching temperature dependence of the intensity of the optical absorption peak due to the complexes. The formation energy of V in high-purity silicon was determined to be about 4.0 eV. This value is in good agreement with results of recent theoretical calculations.

We studied point defects generated by electron-irradiation of hydrogenated Si crystals at low temperatures from the measurement of optical absorption due to hydrogen bound to point defects. Specimens of high-purity, n-and p-type floating-zone grown Si crystals were doped with H by heating in H 2 gas at 1300°C followed by quenching. Then, they were irradiated with 6 MeV electrons at 270, 200 and 130 K. We measured their optical absorption spectra at 7 K with the use of an FT-IR spectrometer. The relative mobilities of various point defects were discussed from the relative intensities of 1838, 1987 and 2122 cm −1 peaks which are due to H 2 *, IH 2 and VH 2 , respectively, where V, I and H 2 * denote a vacancy, a self-interstitial and H 2 in metastable state formed by a reaction between an H 2 and a Frenkel pair, respectively.

We attempted to detect changes in an ESR signal from the excited triplet state of a vacancy oxygen pair in FZ-Si samples caused by doping with hydrogen or deuterium prior to electron irradiation. The presence of vacancy-di-hydrogen (vacancy-di-deuterium) complexes in the doped samples was confirmed by the analysis of infrared absorption spectra. Complete similarity of the parameters and shape of the spectra in the doped samples to that in the reference FZ-Si and Cz-Si samples proves that the signal originates from the same defect for all the cases. Further investigations showed that carrier recombination conditions in the sample and numerous hardly controllable experimental settings affect the shape and intensity of the ESR signal, impeding the correct interpretation of the signal origin.

We studied the TU2 and TU3 ESR spectra from an iron–vacancy pair in iron-doped and electron-irradiated float-zone grown silicon samples. Isotopic shifts in the fine structure term and hyperfine and superhyperfine interaction terms of the spin Hamiltonian are considered in detail. We obtained that the change in the spin value of the defect is accompanied by a modification of the iron atom position. The existing model fails to explain observed large anisotropy of the isotopic effect.

Local mode spectroscopy and ab initio modelling are used to investigate two trigonal defects found in carbon-rich Si into which H had been in-diffused. Isotopic shifts with D and 13C are reported along with the effect of uniaxial stress. Ab initio modelling studies suggest that the two defects are two forms of the CH 2 ∗ complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si, respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed.

A complex magnetic resonance study (EPR, electrically detected EPR, ENDOR) of hydrogen-related radiation-induced shallow donors in silicon has been performed. Three species of this donor family (D1–D3) were observed earlier by means of infrared absorption measurements in hydrogenated Czochralski-grown Si crystals after irradiation with fast electrons and subsequent annealing in the temperature range of 300–550°C. Hydrogen incorporation into the D1 and D2 centers was confirmed by the observation of resonance lines due to hyperfine (hf) interactions of an unpaired electron with the 1H and 2H nuclei in ENDOR spectra. Parameters of the hf interactions were determined from the analysis of angular dependencies of the ENDOR lines. The observed EPR and ENDOR signals are compared with those due to Si-NL10(H) shallow thermal donors and possible atomic structures and formation mechanisms of the defects, which give rise to these spectra, are discussed.

We studied thermal stabilities, electronic and vibrational optical absorption spectra of Be–H and Zn–H complexes in Si. High-purity FZ-Si specimens were doped with Be (or Zn) and H (and/or D) by heat-treatment at high temperatures. Optical absorption spectra of specimens were measured at about 6 K with use of an FT-IR spectrometer equipped with a continuous-flow type liquid helium cryostat. From the analysis of isochronal annealing behaviors, the binding energies of BeH 2 and BeH were determined to be about 2.3 and 3.3 eV, respectively. Some optical absorption peaks of BeH & BeD pairs and ZnH & ZnD pairs were well analyzed by the electronic transitions in tunneling hydrogen-hole interaction system.

An infrared absorption study has been carried out on hydrogen-doped Si crystals with high carbon content. Hydrogen (deuterium) was introduced into the crystals by high-temperature (1250–1350°C) in-diffusion from H 2 (D 2 ) gas ambient. After hydrogenation several local vibrational mode lines were observed in the ranges of 660–690, 790–820, 1920–1960, 2120–2230, and 2680–2950 cm −1 . Two Si–H (Si–D) lines with frequencies at 792.0 (571.6) and 1921.8 (1401.2) cm −1 were found to have the same dependence on hydrogenation temperature and the same annealing behaviour, therefore they were assigned to a single defect. Measurements on samples co-doped with hydrogen and deuterium revealed the appearance of new lines at 793.2, 1400.3, and 1922.7 cm −1 indicating that the defect of interest incorporates two weakly interacting hydrogen atoms. Uniaxial stress measurements showed that the 792.0 cm −1 line represents an E mode (two-fold degenerate) of a trigonal centre. A correlation was found in annealing behaviour of the lines at 792.0 and 1921.8 cm −1 with that of a line at 2752.3 cm −1 . The lines at 792.0 and 1921.8 cm −1 were assigned to Si–H bend and stretch modes, respectively, and the line at 2752.3 cm −1 to a C–H stretch mode of a CH 2 * complex with C 3v symmetry. One hydrogen atom of the complex is bound to a C atom and locates on C 3v axis close to bond-centre site, and the other is bound to a Si atom and locates at an antibonding site.

The formation kinetics of small oxygen clusters in hydrogenated Si has been studied by means of infrared absorption measurements. Hydrogen was introduced into the crystals by in-diffusion from H 2 gas at 1200–1300°C. The samples were heated at temperatures in the range of 280–370°C for different durations. At initial stages of heat-treatment, enormous generation rates of the oxygen dimer have been observed in hydrogenated samples. This indicates highly enhanced diffusion of the interstitial oxygen atoms. The maximum achievable concentration of the dimers is found to be limited by their dissociation rate even at temperatures of about 300°C, while in as-grown crystals the capture processes are known to be dominant in this temperature region. An explanation of this phenomenon is presented.

Optical absorption spectra and the annealing behavior of hydrogen (H)-point defect complexes in carbon (C)-doped Si after hydrogenation were investigated. Specimens of C-doped Si (C concentration: 1.7×1017 cm−3) were sealed in quartz capsules together with H2 gas and were annealed at a high temperature for 1 h followed by quenching in water. We measured the optical absorption spectra at about 7 K with a Fourier-transform infrared spectrometer. The VH4 (V: monovacancy) defect was almost annealed out at 600 °C. The formation energy of the VH4 defect in C-doped Si was estimated to be about 3.2 eV from the quenching temperature dependence of the 2223 cm−1 peak. The observed 2192 and 2203 cm−1 peaks are probably due to the VH3 defect, which captures one H atom during annealing and become the VH4 defect. After annealing at 700 °C, we observed two absorption peaks at 2093 and 2086 cm−1, which are probably due to Si–H stretching vibration of H on internal surfaces of voids. From these assignments, it was found that V is introduced into C-doped Si at high temperatures, although it is known that C introduces I into Si at high temperatures.

The interaction of hydrogen with radiation-induced defects (RD's) in Czochralski-grown silicon crystals has been studied by infrared-absorption spectroscopy and ab initio modeling. Hydrogen and/or deuterium was introduced into the crystals by indiffusion from ${\mathrm{H}}_{2}$ $({\mathrm{D}}_{2})$ gas at $1200--1300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The samples were subsequently irradiated with fast electrons $(E=2\ensuremath{-}4 \mathrm{MeV})$ and annealed in the temperature range of $100--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The centers produced by the irradiation were the same in both the untreated and treated cases, namely the A-center, ${\mathrm{C}}_{i}\ensuremath{-}{\mathrm{O}}_{i}$ complex, and divacancy. A heat treatment of the H-treated samples resulted in the enhanced loss of these centers and the formation of centers containing hydrogen. The disappearance of the A centers in the temperature range of $100--150\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ is correlated with the appearance of three local vibrational modes (LVM's) at 943.5, 2126.4, and $2151.5 {\mathrm{cm}}^{\ensuremath{-}1}.$ The isotopic shifts of these lines were obtained from measurements on the samples doped with hydrogen and deuterium. The lines are identified as related to stretching vibrational modes of a complex that consists of one oxygen and two hydrogen atoms sharing a vacancy site $(V\ensuremath{-}\mathrm{O}\ensuremath{-}{\mathrm{H}}_{2}$ complex). Ab initio calculations are used to explore the structures and properties of this defect. The origin of other LVM bands, which were observed upon annealing, is discussed.

Several pairs of (1 0 0)Si wafers were directly bonded with known misorientation angles, between 0.1 and 11°, to form artificial twist boundaries. The structure and electrical property of these boundaries were studied by means of transmission electron microscopy (TEM) and electron-beam-induced-current (EBIC) method. TEM images showed that the dominant defects at boundaries were screw dislocations which compensate the twist component. All the twist boundaries were EBIC active at room temperature and their contrast values have increased with the increase in the twist angle. The EBIC profiles of twist boundaries were well fitted with the Donolato's model. Although EBIC contrasts of all the boundaries increased with decreasing temperature, the increase of 0.1° boundary was the most significant. Such temperature dependencies indicates that shallow levels are dominant in the smaller angle boundaries, while certain amounts of deep levels are introduced in larger angle boundaries due to dislocation interaction.

To study the generation of interstitials and vacancies due to oxidation of silicon crystals, we applied a quenching method, namely, oxidation at high temperatures in mixed gases of water vapor and hydrogen gas followed by the quenching into water. Contrary to our expectation that the interstitial concentration is high, the vacancy concentration generated due to the short period of oxidation is higher than that of the thermal equilibrium concentration.

We investigated the point defects, which exist at high temperatures in C-doped Si. Specimens were prepared from a floating-zone grown Si crystal doped with C (C concentration: 1.7×1017 cm−3). They were sealed in quartz capsules together with hydrogen (H) gas, with pressure of 1 or 0.8 atm at high temperature, and were annealed at high temperature for 1 h followed by quenching in water. We measured their optical absorption spectra at about 7 K with an FT-IR spectrometer. Several peaks coincided with those observed in proton-implanted Si. We concluded that H-point defect complexes exist in those specimens. In C-doped Si, VH4 (V: monovacancy) defects are formed by the reaction between VH3 defect and H during quenching or annealing. The formation energy of V obtained in this study is smaller than the calculated one in intrinsic Si crystal by more than 1.5 eV.

We studied electronic and vibrational properties of Zn–H complexes in Si based on optical absorption measurements. Specimens were prepared from floating-zone grown Si crystals of high purity and n-type. They were doped with Zn at 1200°C by the vapor pressure method. They were then doped with H and/or D by annealing in H 2 and/or D 2 gas followed by quenching. Optical absorption spectra were measured by an FT-IR spectrometer equipped with a continuous-flow-type liquid He cryostat. When specimens were doped with H at 1200°C, we observed optical absorption peaks due to electronic transition associated with the Zn–H pair. When specimens were doped with H at higher temperatures, intensities of above peaks decreased and two other peaks appeared at about 2214 and 2135 cm −1 , due to the vibration of the Zn–2H complex. The Zn–2H complex dissociated into Zn–H and H at around 450°C and the Zn–H pair dissociated at around 750°C due to isochronal annealing.

We have studied the photoluminescence (PL) properties of Ge-doped GaAs crystals to confirm the validity of a theory developed by Shklovskii and Efros to explain the donor–acceptor pair (DAP) recombination in potential fluctuation. GaAs crystals doped with Ge of various concentrations were grown by a liquid-encapsulated Czochralski method. They were homogenized by annealing at 1200°C for 20 h under the optimum As vapor pressure. Both quasi-continuous and time-resolved PL spectra were measured at 4.2 K. The quasi-continuous PL spectra showed that the peak position shifted to lower energy as the Ge concentration increased, which was consistent with the Shklovskii and Efros's theory. Under very strong excitation in time-resolved measurements, the exciton peak appeared within short periods after excitation and then the peak shifted to that of DAP recombination. This clearly showed that the potential fluctuation disappeared under strong excitation and then recovered as the recombination proceeded.

The shape of the electrically detected magnetic resonance (EDMR) signal from iron–contaminated Czochralski-grown silicon (CZ–Si) samples strongly depends on the thermal treatments applied to the samples before and after the contamination procedure, although the average g-value of the spectra apparently does not vary. A signal from an iron-contaminated float-zone grown silicon (FZ–Si) sample was detected employing an EDMR signal detection unit with enhanced sensitivity. For similar contamination levels, the signal from the FZ–Si sample has amplitude about 1 45 that of the CZ–Si signal and has specific shape. Further study of the EDMR signals from iron-contaminated Si samples will be useful for the investigation of gettering and recombination processes in Si wafers. Besides that, dependence of the EDMR spectrum shape on the thermal processes employed can help to pinpoint the process responsible for wafer contamination during semiconductor device fabrication.

H 2 molecules, which are introduced into moderately doped silicon crystals by high-temperature in-diffusion from H 2 gas ambient followed by fast cooling to room temperature, are found to interact effectively with the defects induced by irradiation of the crystals with fast electrons. In Czochralski-grown silicon crystals, the interaction of the mobile H 2 molecules with vacancy-oxygen defects (A centers) leads to the creation of V–O–H 2 complexes. This complex gives rise to infrared (IR) absorption lines at 943.5, 2126.4, and 2151.5 cm −1 . Ab initio calculations showed that the most stable configuration of V–O–H 2 consists of one oxygen and two hydrogen atoms sharing a vacancy site. It is suggested that the interaction of the V–O–H 2 complexes with interstitial oxygen atoms results in the formation of V–O 2 –H 2 complexes, which are responsible for the IR absorption line at 891.5 cm −1 .

The annealing behaviors of H-point defect complexes in Si were investigated to determine their formation or dissociation processes. Specimens were doped with H by annealing in H 2 gas followed by quenching. They were then irradiated by 3 MV electrons at room temperature. Subsequently, they were annealed isochronally or isothermally. Optical absorption spectra of H-point defect complexes were measured at 7 K. Due to isochronal annealing, the 2122, 1838 and 817 cm −1 peaks disappeared below 200°C. On the other hand, 2223 and 2166 cm −1 peaks were formed at above 125°C and 175°C, respectively. From isothermal annealing experiments, the binding energies of H ∗ 2 (1838 cm −1 peak) and I (I: a self-interstitial)·2H complex (1987 and 1990 cm −1 peaks) were determined to be about 1.5 and 2.0 eV, respectively. The generation of the 2223 cm −1 defect, V.4H (V: a vacancy), was due to the reaction between H 2 and the 2122 cm −1 defect, V·2H.

We determined the formation energy of self-interstitials in carbon (C)-doped Si from measurements of optical absorption due to hydrogen (H) bound to isolated self-interstitials. Specimens of C-doped Si were sealed in quartz capsules together with hydrogen (H) gas, with pressure being 1 atm at high temperature, and were annealed at high temperature for 1 h followed by quenching in water. We measured their optical absorption spectra at about 7 K with an FT-IR spectrometer. Several peaks coincided with those observed in proton-implanted Si. Hence, we conclude that complexes of simple point defects such as vacancies and self-interstitials with hydrogen atoms existed in those specimens. From the quenching temperature dependence of the peaks identified to be H bound to self-interstitials, the formation energy of self-interstitials in C-doped Si was estimated to be about 3 eV.

Formation kinetics of oxygen–hydrogen (deuterium) complexes which give rise to an infrared absorption line at 1075.1 (1076.4) cm −1 have been studied with a method of isothermal annealing in the temperature range of 30–150°C in Czochralski-grown Si crystals with different oxygen content. It was inferred that the capture of mobile hydrogen molecules (H 2 ) by interstitial oxygen atoms accounts for the considered formation kinetics. The values of diffusivity of hydrogen (deuterium) molecules and binding energy of O i –H 2 (D 2 ) complex were estimated from the analysis of the results obtained.

An absorption line at 1025.5 cm −1 has been found in hydrogenated Czochralski-grown Si crystals after irradiation with fast electrons and annealing in the temperature range 300–400°C. Substitution of hydrogen by deuterium resulted in a shift of the band to 1027.9 cm −1 , which clearly indicates H(D) incorporation into the defect which gives rise to the band. It is found that the line is related to a local vibrational mode (LVM) due to a DX-like center, having a shallow donor and a deep acceptor level. The LVM band is observed only when the center is in the singly negatively charged state. Transformation of the defect into the neutral state resulted in disappearance of the LVM band and appearance of several absorption lines in the range 245–325 cm −1 . These lines were interpreted to be associated with ground-to-excited-state electronic transitions in an effective-mass-like shallow donor state of the defect. The structure of the center is discussed.

To estimate the concentration of single vacancies in slowly cooled Si crystals, we calculated the diffusion length and pair formation of vacancies during cooling. The results showed that the concentration of quenched-in single vacancies at room temperature was much lower than that at high temperature.

An absorption line at 1025.5 cm−1 has been observed in hydrogenated Czochralski-grown silicon crystals after irradiation with fast electrons and following annealing in the temperature range of 300–400 °C. The line was found to be related to a local vibrational mode (LVM) due to a DX-like hydrogen-related center, having a shallow donor and a deep acceptor electronic level. This LVM band was observed when the center was in the singly negatively charged state. Transformation of the defect into the neutral charge state due to photoionization resulted in disappearance of the LVM line and the appearance of several absorption lines in the range of 250–325 cm−1. These lines were interpreted earlier to be associated with ground-to-excited-state electronic transitions in an effective-mass-like shallow donor state of the center. Substitution of hydrogen by deuterium resulted in a shift of the LVM band to 1027.9 cm−1 that unambiguously indicates hydrogen incorporation into the defect. The structure of the center whic...