bluuebunny/crossref_metadata_2025 huggingface dataset:
Point Defect Assisted Crystal Growth of Bulk ZnSe
Authors: Terashima K. , Toklzaki E. , Kondo H. , Tanigawa S. , Uedono A. , Watauchi S. , Ujihira Y.
Published: September 2012

Bulk ZnSe single crystals were grown by annealing a CVD grown polycrystalline ingot in a selenium atmosphere for two weeks at 1000°C. To identify the defect structures closely related to the observed grain growth, point defects in bulk ZnSe were subsequently investigated using the positron annihilation technique. A striking result has been obtained; the selenium interstitial type defects were dominantly observed in the crystals grown under a selenium ambient. The fraction of annihilations from the trap states at selenium interstitial type defects in ZnSe increased with increasing the selenium pressure in the annealing ampoule. These results indicated that selenium interstitial type defects enhanced the atomic migration in the crystal and strongly assisted the recrystallization by dislocation climb.
Microstructural and Microchemical Characterisation of CuInSe2 Ingots Grown by the Vertical Bridgman Technique
Authors: Mullan C. A. , Casey S. M. , Jones C. , Kiely C. J. , Imanieh M. , Tomlinson R. D.
Published: September 2012

The microstructure and microchemistry of a number of melt textured CuInSe2 ingots prepared from a variety of starting charge compositions have been investigated using a combination of TEM, EPMA and Auger spectroscopy. If a stoichiometric starting mixture is used, In-rich and Cu-rich precipitates are found at the first and last to freeze zones of the ingot respectively, accompanied by an intervening mid-portion of inclusion free (although slightly off-stoichiometry) CuInSe2 We have found that in order to achieve an optimum matrix composition, a Cu-rich charge is required; however, this leads to a fine distribution of copper selenide particles throughout the ingot. If the starting charge is In-rich, then the boule contains In-rich precipitates and the matrix composition is In-rich and Cu-deficient. These observations are correlated with the observed electrical characteristics of the boules.
Stability Against Concentration Fluctuations in Compound Semiconductors
Authors: Desre P. J.
Published: September 2012

The variation of the composition within the narrow range of off stoic hiometry allowed for compounds is determinant for the population of various intrinsic point defects. As such concentration fluctuations result in inhomogeneities of defect distributions. On the basis of statistical thermodynamics, applied to concentration fluctuation analysis in the III-V compounds, a thermodynamic stability length is defined and calculated as a function of temperature for GaAs, GaSb and GaP. This thermodynamic stability length defines the scale above which full composition homogeneity is unattainable.
Thermal Stability of SiHn Configurations in Fz Silicon Single Crystals
Authors: Kouketsu Masami , Isomae Seiichi
Published: September 2012

Thermal stability of SiHn (n=1∼4) configurations in FZ silicon crystals grown in Ar/H2 has been investigated by means of infrared absorption spectroscopy. Infrared absorption peaks at 2210, 2192, 2123 and 1946 cm−1, which are due to SiH4, SiH3, SiH2 and SiH units in silicon lattice, has been observed. It is found that the concentration of SiH4 and SiH increase with the decrease in SiH2 and SiH3 concentration at 500°C, and vice versa at 600°C. Annealing results suggest thermally induced structural transformations of SiHn configurations. We propose a model of the transformations through the cleavage of adjacent Si-H bonds to form a Si-Si bond and a H2 molecule, as well as the reaction of a H2 molecule with a Si-Si bond.
Impurity and Stoichiometry Control in Atomic Layer Epitaxy
Authors: Yokoyama H. , Ikuta K. , Inoue N.
Published: September 2012

We investigate the intrinsic point defects in epilayers grown by atomic layer epitaxy (ALE). Ga vacancies and antisite As atoms in the epilayers are detected by photoluminescence spectroscopy. This shows that the ALE epilayer was grown under As-rich conditions. We propose increasing the TMG flux to reduce the number of point defects. With this method, the number of point defects in ALE epilayers can be decreased to less than that in conventionally grown epilayers. Moreover, it is'found that these point defects are formed by the incomplete Ga coverage, not by the steric hindrance as previously suggested. The carbon concentration is decreased by one order of magnitude by using nitrogen instead of hydrogen as the carrier gas. As an application of this low defect density, we fabricated a GaAs/AlAs resonant tunneling diode and observed the negative resistance at room temperature.
Thin Oxide Defects Resulting from Plasma Induced Wafer Charging
Authors: Fang Sychyi , McVittie James P.
Published: September 2012

EEPROM charge monitors reveal that an O2 plasma induces a negative charge which peaks at the wafer center for the asher used. The charge damage to small gate area MOS capacitors is investigated by using “antenna” structure. The post plasma interface state density increases with increasing antenna size and varies by two orders of magnitude. A hole trapping induced breakdown mechanism during plasma charging is supported by new experimental evidence such as the annealing and polarity effects of charge-to-breakdown and tunneling currents. Where stressing has not being severe, these hole traps are annealable at T > 650°C, while in severely stressed areas early breakdown occurs which is not annealable.
Optimization of MBE of CdTe/CdTe: Refinement in Structural Quality Evaluation of MBE Grown (111) CdTe
Authors: Lee M. B. , Fanning T. , Di Marzio D. , Casagrande L. G. , Dudley M.
Published: September 2012

A detailed optimization of MBE growth of CdTe on CdTe (111)β using white beam synchrotron x-ray topography, and x-ray rocking curve analysis has been carried out. Defect structures in (111)5 substrates and epilayers are imaged with white beam topography and, for the first time, direct observation of stress induced microtwin growth in CdTe epilayers has been made. X-ray rocking curve analysis of CdTe substrates is shown to be relatively insensitive to defect structures consisting of dislocations and inclusions. On the other hand rocking curve analysis of (111) epilayers reveals a sensitivity to the presence of microtwin. The defect microstructure of a CdTe (111)Bepilayer with the narrowest rocking curve FWHM value published to date (9.4 arc-sec) will be discussed.
Mosaic Spread of the Heteroepitaxial Structures from Renninger Scan
Authors: Morelhão S. L. , Cardoso L. P.
Published: September 2012

In this work, a method of obtaining mosaic spread of the heteroepitaxial structures using Renninger scan (RS) peak profiles is reported. A simulation program was developed in order to account for the influence of the wavelengths, incident beam divergence, sample mosaic spread (layer and substrate) in the profile of the RS peaks. Surface three beam multiple diffraction cases with a forbidden or even very weak primary reflections are used to provide simpler intensity expressions and high intensity in RS. GaAs/Si samples have been analyzed as an application of this method.
Noble Gas Incorporation in Sputtered and Ion Beam Assisted Grown Silicon Films
Authors: van Veen A. , Greuter M. J. W. , Niesen L. , Nielsen B. , Lynn K.G.
Published: September 2012

Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self- interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.
Atomic Structures of Planar Defects in Si and GaAs
Authors: Takeda S. , Muto S. , Hirata M.
Published: September 2012

Atomic structures of planar defects in Si and GaAs have been studied by TEM. An HREM image of the edge of {113} planar defect has been obtained with <110> incidence. An analysis of the image has showed diat the edge consists of 5-, 6- and 7-membered rings without dangling bond. Anisotropie morphology of the defect could be understood from the model proposed in this report. Weak diffuse scattering and an extinction rule in diffraction patterns from the defect have been found. The experimental evidence has supported the model of the {113} defect.

A planar defect on {111} in a heavily Si doped GaAs has been studied. The result has indicated that Si precipitates on the two {111} net planes inserted in the GaAs matrix.
Recombination Activity of Individual Extended Defects in Silicon
Authors: Cavallini A. , Castaldini A.
Published: September 2012

Dislocations and point defects introduce energy levels deep in the gap, which dramatically change the material electrical properties. Because of the coexistence of a multitude of dislocation types and dislocation-point defect interaction mechanisms, it would be highly desirable to identify the particular type of defect related to specific traps.

The electrical activity of extended defects (planar precipitates and dislocations) is here examined in terms of their recombination activity, investigated by electron as well as light beam induced current methods of scanning microscopy.

Besides, a scanning modification of spectroscopy is used to identify traps at individual defects. The method, named quenched infra-red beam induced current, combines the scanning light beam induced current technique with the spectroscopie bulk analysis called “infrared quenching of photoconductivity”.

Defect energy levels are found on the basis of the particular features of the beam induced current as a function of injected carrier generation rate, temperature and quenching excitation.
Evaluation of Vacancy-Type Defects in Simox Substrates by a Slow Positron Beam and a Pulsed Positron Beam
Authors: Kametani H. , Akiyama H. , Yamaguchi Y. , Koumaru M. , Wei L. , Tabuki Y. , Tanigawa S. , Uedono A. , Watauchi S. , Ujihira Y. , Suzuki R. , Ohgaki H. , Mikado T.
Published: September 2012

Slow/monoenergetic positron beams and pulsed positron beams have been used as a non-destructive probe to investigate vacancy-type defects in SIMOX substrates which were formed by high - dose oxygen implantation and high-temperature annealing. To obtain depth profiles of vacancy-type defects, a positron beam in the 0–30keV energy range was used. Doppler broadened annihilation spectrum and positron lifetime were measured as a function of incident positron energy. These measurements show the following results; vacancy -type defects exist near the surface of the top silicon layer even if the specimen was analyzed as defect -free Silicon by XTEM, and in the case of the as-implanted specimen, cavities in diameter of about 50–200A are created in the top silicon layer and they include high pressure gases.
Transmission Electron Microscopy of Hydrogen-Induced Defects in Low Temperature Epitaxial Silicon
Authors: Anderson G. B. , Tsai C. C. , Thompson R.
Published: September 2012

Hydrogen is commonly used in crystalline Si for passivation of defects and impurities. When single crystal Si undergoes a post-hydrogenation step, hydrogen-induced platelets have been shown to form in the first 100 nm of the Si. The same hydrogen platelets occur in homoepitaxial Si grown by low temperature (350°C or below) plasma-enhanced chemical vapor deposition with hydrogen dilution. This study has used transmission electron microscopy (TEM) to examine the structure of these hydrogen-induced platelets. TEM has shown that the platelets generally grow in tne (111) crystal planes of the Si. The size of the platelets, which ranges from 5 to 100 nm, increases with growth temperature but the density of platelets decrease at higher growth temperatures. The hydrogen platelets are not confined to the epitaxial Si layer only but also grow into the substrate. High resolution TEM shows the platelets dilate the silicon lattice by approximately 60% of a Si <111> plane. TEM has also shown that platelets cause no net displacement of the local Si lattice. Tilting experiments performed in the TEM show that the platelets are composed of a circular two-dimensional structure. Our results indicate that the hydrogen-induced platelets found in low temperature epitaxial Si are structurally the same as those seen in crystalline Si that has undergone post-hydrogenation processes.
Influence of Surface Relaxation and Multi-Dislocation Strain Field Interactions on X-ray Topographic Images of Dislocations in Semiconductor Materials
Authors: Wu Jun , Fannin Thomas , Dudley Michael , Shastry Vijay , Anderson Peter
Published: September 2012

Analysis of the white beam synchrotron x-ray topographic contrast behavior of screw dislocations comprising slip bands in silicon, observed under low absorption conditions, is presented. For both individual and groups of dislocations, observed “Direct Image” contrast at the surface intersections of dislocation lines, on reflections for which g·b=0, could be accounted for using equi-misorientation contour analysis using displacement fields which take surface relaxation effects into account. This contrast is shown to be a sensitive function of the local stress environment. In addition, diffuse area contrast observed within and in the vicinity of slip bands on such reflections is also observed to be very sensitive to long range strain fields associated with adjacent slip bands and other defects in the local slip band environment.
Infrared Absorption by Free Carriers in Si and Influence on Oxygen Determination by Ftir-Spectroscopy
Authors: Koster L. , Bittersberger F.
Published: September 2012

Using FTIR-spectroscopy for the determination of the oxygen content in CZ Si, an additional absorption of IR light occurs for doping densities above 1015/cm3, which is caused by the free carriers. It increases nearly linearly with the carrier density and reduces multiple reflections within the sample. Excessively low oxygen values are obtained if this effect is neglected. The deviation from the true values can amount up to 15 % and depends on carrier density, type of doping, oxygen content and sample thickness. Measurements of the absorption coefficient induced by the free carriers were performed for p-and n-type FZ material in dependence of the IR wavelength and of the doping concentration. The obtained values at the wavelength of the oxygen absorption band (1107 cm−1) were used to calculate correction factors for the oxygen content in the doping range from 1 * 1017 to 1 * 1015/cm3. An example shows that the correction reaches 5 % for carrier densities of 1 * 1017/cm3, n-type and 2 * 1016/cm3, p-type, respectively, for an assumed sample thickness of 0.7 mm.
Characterization of Defects in Heavily Si-Doped GaAs by A Monoenergetic Positron Beam
Authors: Uedono A. , Ujihira Y. , Wei L. , Tanigawa S.
Published: September 2012

Native defects in Si-doped, Zn-doped and undoped GaAs grown by horizontal Bridgman (HB) method and molecular beam epitaxiy (MBE) were studied by a monoenergetic positron beam. Positron lifetime spectra and Doppler broadening profiles were also measured by using energetic positrons. It was found that monovacancies were usually found in Si-doped HB-GaAs, however, divacancies were created in a specimen with low impurity concentration. For Zn-doped HB-GaAs, interstitial clusters were found to be major type of defects. The high concentration of monovacancies and of divacancies coexist in heavily Si-doped MBE-GaAs. These vacancy-complexes were found to act to reduce the concentration of free carriers.
EL2 Related Anomalous Splitting in the Photoreflectance Response of Semi-Insulating GaAs
Authors: Durbin C. , Estrera J. , Glosser R. , Duncan Walter , Henry R.L. , Nordquist P. , Bottka N. , Gaskill D.K.
Published: September 2012

Anomalous splitting has been observed in the photoreflectance (PR) response of SI:GaAs in the vicinity of the exciton at 78 K. Recent photohiminescence (PL) measurements suggest the splitting is correlated with the EL2 content of the samples. Separation between the two peaks in PR measurements range from about 2 to 4 meV. A striking effect is that each peak is maximized by a different phase setting of the lock-in. The splitting is sample dependent and is also affected by several other factors including surface conditions, temperature, pump beam intensity and modulation frequency.
Dynamic Behavior of Intrinsic Point Defects in Fz and Cz Silicon Crystals
Authors: Abe Takao , Takeno Hiroshi
Published: September 2012

Detaching the crystals from the melt revealed the real state and dynamic change of intrinsic point defects. From this observation it is confirmed that the predominant point defects near the melting point are vacancies. Clusters of interstitial-type dislocation loops (CDL) are eliminated by taking an extremely low growth rate under 0.2 mm/min and nitrogen doping. The anomalous oxygen precipitate (AOP) of the crystals grown in a nitrogen ambient is enhanced. AOP and ring-oxidation induced stacking fault (R-OSF) coexist at the periphery in nitrogen doped crystals. Almost all crystals have defect boundaries between periphery and center region which may be attributed to a stress field in the crystals during growth.
Characterization of Metal-Oxide-Silicon Interface by Monoenergetic Positron Beam
Authors: Ohji Yuzuru , Uedono Akira , Wei Long , Tabuki Yasushi , Tanigawa Shoichiro
Published: September 2012

MOS device interfaces are investigated using carrier injection and monoenergetic positron beam experiments. Carrier injection reveals that the holes injected into gate S1O2 film seem to be the main cause of the interface state generation and the dielectric breakdown of thin-gate SiO2. Positron annihilation experiments show that the positron diffuse along the electric field in the Si and the gate SiO2 and are trapped in the interface region before annihilation. The obtained value of 5 at the SiO2/Si interface was 0.500 ±0.003. The behavior of holes in the SiO2 and SiO2/Si interface are simulated using the monoenergetic positron annihilation technique.
Defects Introduced by Low Dose Be-Implantation Probed by a Monoenergetic Positron Beam
Authors: Uedono A. , Ujihira Y. , Wei L. , Tabuki Y. , Tanigawa S. , Wada K. , Nakanishi H.
Published: September 2012

Vacancy-type defects in 60-keV Be+-implanted GaAs and InP were studied by a monoenergetic positron beam. The depth distributions of vacancy-type defects were obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. Vacancy-type defects introduced by ion implantation were observed in n-type GaAs. For p-type GaAs, however, this was not the case. This can be attributed to the recombination of vacancy-type defects and pre-existed interstitial-type defects in p-type GaAs. The defects induced by ion implantation in InP were also studied.
Positron Annihilation and Electron Spin Resonance of Electron-Irradiated 3C-SiC
Authors: Itoh Hisayoshi , Yoshikawa Masahito , Wei Long , Tanigawa Shoichiro , Nashiyama Isamu , Misawa Shunji , Okumura Hajime , Yoshida Sadafumi
Published: September 2012

Positron annihilation and electron spin resonance (ESR) have been used to study defects introduced by lMeV electron irradiation in n-type cubic silicon carbide (3C-SiC) epitaxially grown on Si by chemical vapor deposition. Positron annihilation measurements by using variable-energy positron beams indicated the narrowing of the Doppler-broadened energy spectrum of annihilation gamma-rays and the decrease in the effective diffusion length of positrons with increasing the electron fluence. These results show the formation of vacancy-type defects in 3C-SiC. An ESR spectrum labeled T1, which has an isotropie g-value of 2.0029±0.0001, was observed in electron irradiated 3C-SiC. The T1 spectrum is interpreted by hyperfine interactions of paramagnetic electrons with 13C at four carbon sites and 29Si at twelve silicon sites, leads that the Tl center results from a point defect at a silicon sublattice site. The production rate of the Tl center was in good agreement with the carrier removal rate, indicating that the Tl center captures an electron from the conduction band. All these results are accounted for by the introduction of negatively charged vacancies at silicon sublattice sites in 3C-SiC by the irradiation.
Hydrogen in Compound Semiconductors
Authors: Johnson N. M.
Published: September 2012

Phenomena associated with hydrogen in compound semiconductors include the formation of complexes with both dopant impurities and deep-level defects, the generation of hydrogen-related deep-level defects, and the migration of isolated hydrogen as a charged species. In addition to reviewing these phenomena, this paper describes the depletion-layer technique for determining thermal dissociation energies of hydrogen-impurity complexes and presents an updated tabulation of the parameters that have thus far been obtained from experimental studies to quantitatively describe hydrogen-dopant complexes and hydrogen migration in GaAs.
Characterization of Defects in CZ-grown Si Crystals with OSF Ring
Authors: Ogushi Satoshi , Hourai Masataka , Shigematsu Tatuhiko
Published: September 2012

The nature and radial distribution of crystallographic micro-defects in CZ-grown silicon crystal wafers which exhibit OSF ring were investigated. With the difference in copper decoration XRT image and in temperature dependence of oxgen precipitation, four coaxial ring regions were clearly identified. In the OSF ring region, oxgen precipitation takes place even at relatively high temperatures around 1, 100°C. Gold diffusion experiments were also carried out, for which the ‘kick-out mechanism’ was considered to reveal the density distribution of sinks for interstitial silicon. A semi-quantitative schematic model describing the density distribution of the precipitation nuclei as a function of critical size of the nuclei for each of the four ring regions is derived. The nuclei that are stable at high temperature act as sinks for interstitial silicon atoms, generating stacking faults.
Thermal Stabilttx of Hxdrogbnation Processes into Multicrystalline Silicon
Authors: Muller Jean-Claude , Hartiti Bouchalb , Younis Hussain , Siffert Paul
Published: September 2012

We have compared, for multicrystalline silicon solar cells, the neutralization efficiency of low energy hydrogen ion implantation to those resulting from the deposition of hydrogenated silicon nitride and determined the optimal temperature in order to have the most important improvement of the bulk diffusion length LD.

In particular, the concentration profile of the introduced hydrogen has been determined by means of Elastic Recoil Detection (ERD) or nuclear reaction analysis and the electrical effects of the hydrogen investigated by the Surface PhotoVoltage (SPV) technique.

At least, the stability of the LD improvement after post-thermal treatments around 400°C and at higher temperatures has been studied for two annealing modes using a classical (15 min) or a rapid lamps furnace (25 sec).
Anomalous Behavior in the Resistivity of N-I-N Polysilicon Resistors After Hydrogenation
Authors: Moore Chad B. , Ast Dieter G.
Published: September 2012

Undoped 20 μm thick polycrystalline silicon (polysilicon) films were epitaxially grown on 0.5 μm thick polysilicon seed layers prepared by cycles of CVD depositions and oxidations. The resistivity of the epitaxial films was found to vary by a factor of 4, depending on the number of deposition/oxidation cycles used to prepare the initial seed layer. Exposing the films to a hydrogen plasma for as little as 5 seconds decreased the resistivity of n-i-n resistors by four orders of magnitude and changed their activation energy from 0.4 eV to 0.001 eV. Whereas, the resistivity of p-i-p resistors only decreased by a factor of two after a 2 hour hydrogenation with no change in the activation energy. The initial high resistivity value of the n-i-n resistors was restored by either removing 0.5 μm of polysilicon from the surface of the resistors or by a 15 minute anneal in argon at 550 °C.
Mechanism of Enhanced Hydrogen Diffusion in Solar Cell Silicon
Authors: Sopori Bhushan L.
Published: September 2012

Experimental results that support our previously reported observations of enhanced diffusivity of hydrogen in some solar cell silicon are presented. The diffusivities of hydrogen, implanted at low energies, were measured for several commercial silicon substrates. It is shown that the diffusivity of hydrogen in some solar cell substrates is about two orders of magnitude higher than that in Float Zone silicon in a temperature range of 100° - 300°C. This value of diffusivity is also close to that observed along some grain boundaries in polycrystalline silicon. It is determined that hydrogen in-diffusion is accompanied by an out-diffusion of boron, and that the hydrogen diffusivity is retarded by high concentrations of oxygen. A mechanism for enhanced hydrogen diffusion is proposed which invokes formation of a highly mobile vacancy-hydrogen complex.
The Effect of Hydrogen Treatment on Electrical Properties of AIGaAsSb
Authors: Polyakov A. Y. , Stam M. , Milnes A. G. , Wilson R. G. , Bochkarev A. E. , Rai-Choudhury P. , Hillard R. J. , Pearton S. J.
Published: September 2012

The effect of hydrogen treatment at 200°C on the concentration of electrically active defects in LPE grown AIGaAsSb is reported. In n-type layers the electrical properties are shown to be dominated by DX-like deep donors of three different types all of which are strongly passivated by the hydrogen treatment as evidenced by C-V. DLTS C-T and spreading resistance measurements. In p-type layers intrinsic acceptors of defect origin are also passivated by hydrogen. Deuterium profiles in both n- and p-type layers show characteristic plateaus indicative of formation of neutral compexes between hydrogen and dopants. Hydrogen treatment also leads to decrease of the Au/n-AIGaAsSb Schottky barrier height from 1.3 to 0.85 eV.
Plasma Hydrogenation Studies on Low-Temperature Mbe-Grown GaAs
Authors: Nakagawa O. S. , Ashok S. , Zhang K. , Miller D. L. , Chung W. K.
Published: September 2012

The effect of hydrogen plasma on the electrical properties of low-temperature-grown GaAs (LT-GaAs) is reported. LT-GaAs epitaxial layers, 2μm thick were grown on a <100>, semi-insulating GaAs (SI GaAs) substrate using molecular beam epitaxy (MBE) at 300°C. Some of the samples were annealed in- situ at 600°C for 1 hour. These LT-GaAs samples were then subjected to hydrogen plasma at 300°C in a parallel-plate, low-frequency (30KHz) system for varying times up to a maximum of 13 hours. Current through the LT-GaAs layers as a function of voltage (I-V), temperature (I-T), and time (I-t) was measured between two surface contacts formed by thermal evaporation of Au. Evidence of partical defect passivation found in the electrical characteristics of hydrogenated LT GaAs is presented. These include reduced current at low temperature (<210K) and reduced current activation energy at high temperature (>320K).
Nuclear Magnetic Resonance Studies of Deuterium in Silicon
Authors: Bustillo Karen Carr , Haller Eugene E. , Reimer Jeffrey A.
Published: September 2012

We report nuclear magnetic resonance measurements of deuterone diffused into silicon powders. Deuterium spectra show a two-component lineshape corresponding to two distinct hydrogen sites. The component with a narrow Lorentzian lineshape is assigned to D2 molecules. The second component is a quadrupolar doublet powder pattern, and its characteristic splitting provides a value of the electric field gradient at the site of the deuterium atom of 1.45×105 dyn/cm.
A Study of Defects in Czochralski-Grown Silicon by Positron Annihilation Spectroscopy
Authors: Sharma S. C. , Hozhabri N. , Hyer R. G. , Hossain T. , Kim S. , Meyer F. O. , Pas M. F. , Stephens A. E.
Published: September 2012

We have studied defects in Cz-grown single crystal silicon by utilizing a variable energy positron beam and positron lifetime spectroscopy in conjunction with surface photovoltage measurements. We present results for the depth profile of defects obtained from the Doppler broadening spectra measured by implanting variable energy positrons at different depths ranging from the surface down to ∼ 1 /xm deep. We have also measured positron lifetime spectra at different locations on a wafer and have obtained a radial variation in the density of the vacancy-type defects.
The Electronic States and Dynamical Properties of Hydrogen Bound to Carbon in Silicon
Authors: Kamiura Yoichi , Hashimoto Fumio , Yoneta Minoru
Published: September 2012

This paper demonstrates a unique action of hydrogen on defects and impurities in semiconductors. Hydrogen injected into n-type Si by chemical etching or hydrogen plasma not only pas-sivatcs phosphorus but also electrically activates carbon by forming a H-C complex acting as an electron trap E3 (0.15). A model of the structure and electronic state of the H-C complex is proposed on the basis of available experimental data on the properties of the complex. The diffusion coefficient of isolated hydrogen below 300K is evaluated from its diffusion process to phosphorus after the photoinduccd dissociation of the H-C complex. Some differences in hydrogen diffusion between chemically etched and plasma hydrogenated crystals arc discussed.
Diffusion of Hydrogen and Hydrogen-Dopant Interactions in Si Doped GaAs and GaAlAS Alloys
Authors: Chevallier J. , Machayekhi B. , Grattepain C. , Rahbi R. , Theys B.
Published: September 2012

Deactivation of silicon dopants by hydrogen in GaAs and GaAlAs proceeds through the formation of hydrogen-dopant complexes with thermodynamical and vibrational characteristics weakly sensitive to the alloy composition. However the hydrogen diffusion profile is strongly sensitive to the alloy composition. In GaAs:Si, the profile is an erfc function while in Ga1-xAlxAs:Si with x > xo, it is rather a step like function. From the doping level dependence of xo, we explain the hydrogen diffusion properties within a model where H° and H-govern the diffusion profiles respectively for x < xoand x > xo. We deduce that hydrogen behaves as a deep acceptor in these materials with a level slightly resonant in the conduction band of GaAs and localized in the band gap of Ga1-xAlxAs alloys for x > 0.07.
Optical Emission Study of the Energy Levels of Ga-VACANCY/HYDROGEN Complexes in N and P-TYPE GaAs
Authors: Amore Bonapasta A. , Bonanni B. , Capizzi M. , Cherubini L. , Emiliani V. , Frova A. , Sarto F.
Published: September 2012

The formation of Ga-vacancy/hydrogen complexes in GaAs has been detected via photoluminescence measurements. Different degrees of hydrogénation can be achieved by low-energy H- or D-ion irradiation from a Kaufman source. The volume incorporation, for equal treatment, is dependent upon the density of impurities and defects where H can bind. In originally p-type MBE-GaAs, prolonged hydrogen treatments lead to the appearance of three emission structures in the range 1.15–1.34 eV. The results are explained in terms of transitions to different states of charge of gallium vacancies trapping one or more H-atoms, the activity of the individual states being dependent upon the H-dose and the nature of the laser excitation. The model is supported by comparison with the changes in the Ga-vacancy/donor emission band in degenerate n-type samples, as it evolves, from the virgin condition, through hydrogenation. The present observation provides also valid support to the creation, in p-type material, of a semi-shallow donor associated to H trapped along the As-Ga bond, in the immediate neighborhood of the gallium vacancy.
External Gettering and Hydrogenation Effects on Electrical Properties of Multicrystalline Silicon Wafers
Authors: Perichaud I. , Martinuzzi S.
Published: September 2012

To reduce the density of recombination centers, external gettering by phosphorus diffusion from a POCI3 source and hydrogénation were applied to 200 μm thick samples.

Gettering was carried out at 850°C or 900°C, for 120 or 240 mn. Hydrogénations result of the annealing of samples at 400°C for 30 mn in gas flow. Thanks to arrays of mesa diodes, it is found that minority carrier diffusion lengths (Ln) are neatly improved by the gettering. The improvements are higher at 900°C than at 850°C, they increase with gettering time and SIMS analyses indicate that they are due to the removing of Fe, Cu and Ni atoms.

Hydrogénation enhances Ln values in samples gettered at 850°C and the higher Ln the longer the gettering time. After hydrogénation, the values of Ln in the samples gettered at 850°C are comparable to those measured in samples gettered at 900°C. It is assumed that hydrogen is able to neutralize the activity of impurities which have not been gettered, like oxygen, and also that of residual metallic impurities.
Electrical and Optical Properties of Titanium, Vanadium, Molybdenum, and Tungsten Related Defects in Silicon
Authors: Schmalz K. , Grimmeiss H. G. , Pettersspn H. , Tilly L.
Published: September 2012

Recent studies of the deep transition-metal centers Ti, V, Mo and W in silicon are discussed, which have been investigated using junction-space charge techniques. The changes in the Gibbs free energy, enthalpy, and entropy due to electron or hole excitation of these transition metal related levels are presented. The good agreement of the Gibbs free energies with the optical threshold energies of the corresponding photoionization cross sections suggests negligible lattice relaxation. For the Ti-doped samples three energy levels at Ec-0.065 eV, Ec-0.295 eV and Ev+0.255 eV at 80 k were observed. For Mo and W the energy levels are located at Ev+0.298 eV and Ev+0.379 eV, respectively, at 80 K. Three energy levels of the V-related centers exist at Ec-0.207 eV, Ec-0.483 eV and Ev+0.356 eV at 0 K. A structure in the low-energy part of the spectral distribution of the level Ec-0.483 eV is assumed to be due to excited states and shown to be in good agreement with effective-mass theory. Previous assignments of the energy levels should be reconsidered.
Transformation of Gold in N-Type Silicon from a New Deep Level to the Gold Acceptor Level
Authors: SveinbjöRnsson Einar Ö. , Engström Olof
Published: September 2012

Using deep level transient spectroscopy (DLTS) on gold-doped n-type Czochralski (CZ) and float zone (FZ) silicon we observe a new gold-related acceptor level (G) with an activation energy σn= 0.19 eV and an electron capture cross section On = 1–10-17 cm2. The center anneals out at a temperature of 250°C, simultaneously as the gold acceptor concentration increases. Annealing at temperatures below 250°C does not reverse this process. However, etching a few microns off the sample surface using HF:HNO3 based etch reforms the G center and the gold acceptor concentration decreases accordingly. From DLTS depth-profiling we determine that the new center is only found at depths less than 5 μm, and in the same region we observe neutralization of phosphorus dopants and a reduction in the gold acceptor concentration.

We propose that in-diffusion of hydrogen during the etching process is responsible for the three observed transitions, i.e. neutralization of both phosphorus donors and gold acceptors and formation of the G center. We suggest that there are (at least) two possible Au-H complex centers, one which is electrically inactive and another which gives rise to an acceptor level (ΔE = 0.19 eV) in the bandgap of n-type silicon. The electrically active center anneals out at 250°C while the electrically inactive one is more stable and has been observed earlier in remote plasma hydrogenation experiments performed at 150–350°C.
Proof of the Acceptor State of the Trigonal Iron-Boron Pair in Silicon by Electron Paramagnetic Resonance Measurements
Authors: Gehlhoff W. , Rehse U.
Published: September 2012

For the first time the acceptor state of iron-boron pairs the occurence of which are suggested by electrical measurements and theoretical considerations is directly proved by EPR measurements. The corresponding EPR spectrum is observed upon suitable illumination of samples which have been co-doped with boron and iron. It shows trigonal symmetry, and the fine-structure pattern can be described with the spin S = l, the g-values gi ∼ 2.1345±0.0001, gi = 2.1345±0.0004 and the zero-field splitting parameter |D| = (1.418±0.001) cm−1.
Excitonic Mechanism of Rare Earth Excitation in II-VI and IH-V Semiconductors
Authors: Godlewski Marek
Published: September 2012

In this paper we analyze processes which may improve the efficiency of low- and high- field electroluminescence devices based on rare earth doped II-VI and III-V semiconductors. The main topicsare the processes which follow impact ionization, i.e., carrier trapping and/or exciton binding. Excitonic excitation mechanism is shown to occur also for ions which are not directly ionized, as observed recently for some rare earth impurities in II-VI and III-V semiconductors.
Donor-Acceptor Pairs in Silicon
Authors: Altink H. E. , Gregorkiewicz T. , Ammerlaan C. A. J.
Published: September 2012

Stable forms of donor-acceptor pairs in silicon arise from the interaction between negatively charged acceptors and 3d transition element donors, which, occupying interstitial sites, have high mobilities. The atomic and electronic structure of these pairs can be studied in detail by magnetic resonance. The symmetry of centers as observed in the resonance experiments gives strict constraints on the applicable atomic models. The spin of centers is related to their charge state. Hyperfine interactions frequently lead to a specific structure in the spectra, which characterizes the chemical identity of atomic components of the pair. Deep level transient spectroscopy provides a way of sensitive observation of electrically active impurities: to determine their concentrations and associated electronic levels. It allows the study of the kinetics of the pair formation process and thermally induced dissociation; binding energies can be determined. Transformation of pairs as a result of illumination was also observed. Several of the pairs can exist in geometrically different atomic configurations leading to the phenomenon of bi- or multi-stability. In the paper the donor-acceptor pair formation process is illustrated by examples involving the substitutional double acceptor zinc, for which new data became recently available.
Metastable Defects of Iron-Boron Pair in Silicon
Authors: Nakashima H. , Sadoh T.
Published: September 2012

We have found configuratlonally metastable Fe-B pairs in Si by using dark or photo capacitance-transient technique combined with minority-carrier injection. The metastable pairs are observed as four electron-trapping levels at Ec-0.43 eV, 0.46 eV, 0.52 eV, and 0.54 eV and as two hole-trapping levels at Ev+0.53 eV and 0.48 eV after the injection at 150 K. The production of each level is investigated under various injection conditions, and the annihilation process is studied by isochronal anneals.
Origins of the Gap States in Polycrystalline Silicon: Tight-Binding Calculations of Twist Boundaries
Authors: Kohyama M. , Kose S. , Yamamoto R.
Published: September 2012

The atomic and electronic structures of the twist boundaries Σ (=3 (011), Σ=7 (111) and Σ=5 (001)) in Si have been calculated by using the transferable SETB method coupled with the supercell technique. The twist boundaries in Si contain larger structural disorder or more defects and larger interfacial energies than tilt grain boundaries. Several kinds of structural disorder or defects have been found to generate characteristic electronic states inside the gap. The present structural disorder or defects and the gap states are the candidates of the origins of the observed band-tails or mid-gap states in polycrystalline Si as well as those In amorphous Si.
Effects of Hydrogen or Nitrogen on Growth of Oxygen-Related Defects in Germanium
Authors: Makihara Noboru , Ito Kazuyoshi , Mizuno Kaoru , Ono Kotaro
Published: September 2012

Oxygen-doped germanium crystals were used to demonstrate the interaction between implanted hydrogen or nitrogen atoms and the oxygen-related defects. The electron trap at Eo-0.26eV associated with the germanium A-center was found to be formed by electron irradiation. Another level at Eo-0.21eV also was observed on annealing at 120 °C. As for the sample implanted with hydrogen ions following electron irradiation, the trap concentration is four times as large as that for electron irradiation alone. It is probable that the germanium A-centers produced by electron irradiation capture hydrogen atoms and increase electrically active centers. After nitrogen implantation following electron irradiation, the Eo-0.26eV level almost annealed out at 140 °C and the trap at Eo-0.21eV wasn't observed. We propose that the reduction in the oxygen-related defect growth is due to the prevention of defect migration with nitrogen atoms.
Similarity of Vacancy Creation Mechanisms in Si Doped GaAs and Ga Doped ZnSe Observed by a Monoenergetic Positron Beam
Authors: Tanigawa S. , Lee J. L. , Wei L. , Kawabe M. , Miyahma T. , Okuyama H. , Akimoto K. , Mort Y.
Published: September 2012

The impurity effects on the creation of vacancies in GaAs and in ZnSe were investigated by monoenergetic positron beam measurements. In the case of the Si-doped MBE grown GaAs, the doping of Si atoms was found to enhance the creation of Ga site vacancies. The concentration of Ga vacancies was found to be proportional to the doped Si concentration. The observed linear relation between both concentrations supports the theoretical prediction on the creation of Ga vacancies in terms of the change in the Fermi-level position by the Si doping into GaAs and also suggests that Si atoms diffuse in GaAs as a neutral complex of Ga vacancy-Si pair rather than that of Si-Si pair. In the case of the Ga-doped MBE grown ZnSe, Zn vacancies were found to be generated in proportion to the concentration of doped Ga atoms. The observed similarity of the vacancy creation in the Si-doped GaAs and in the Ga-doped ZnSe can be well explained by the consideration of the charge neutrality condition around impurities.
Ebic Analysis of Gettering at Si-Si (Ge) Heteroepitaxial Misfit Dislocations as a Function of Impurity Decoration
Authors: Kirk H. R. , Radzimski Z. J. , Fitzgerald E. A. , Rozgonyi G. A.
Published: September 2012

An EBIC analysis is made of decorated heteroepitaxial misfit dislocations formed at the interface of Si-Si (Ge) epitaxial layers grown in a CVD reactor on Si substrates. The electrical activity of the dislocations is studied after decorating the dislocations with Ni and Au impurities introduced by ion-implantation and backside deposited metallic thin films. The impurities are activated by RTA annealing at 400, 800 and 1000°C. A model is presented for the formation of NiSi2 precipitates on misfit dislocations which suggests that the nucleation and growth of NiSi2 precipitates is a function of the cleanliness of the as-grown dislocations. It is concluded that the distribution of electrical activity of impurity decorated misfit dislocations is a strong function of the impurity type, condition of the as-grown material, and concentration of metallic impurities introduced during the process of decoration.
Defect Analyses in VLSI Devices by TEM Observation and Process Simulation
Authors: Mikoshiba H. , Nishio N. , Matsumoto T. , Kikuchi H. , Kitano T. , Kaneko H.
Published: September 2012

This paper presents several examples of defect analyses carried out in actual VLSI failure analyses and experiments, using TEM technique, process simulation and other advanced analytical tools. New TEM techniques are also described to observe a precise location which has failed.
Control of Process-Induced Defects in the Formation of Single and Multiple layer dielectric Structures for Si Semiconductor Devices
Authors: He S. S. , Stephens D. J. , Ma Y. , Yasuda T. , Habermahl S. , Lucovsky G.
Published: September 2012

A low-temperature, 200–300°C, plasma-assisted oxidation-deposition process sequence has been developed for formation of SiO2/Si heterostructures. Adding a nitride layer to form an ON, or ONO composite dielectric, increases the density of trapping states, Dit, at the SiO2/Si interface, unless the entire structure is subjected to a high-temperature rapid thermal anneal, e.g., 30 s at 900°C. By interrupting the nitride deposition, and using on-line Auger electron spectroscopy, AES, the increase in Dit correlates with a migration of N-atoms to the SiO2/Si interface during the nitride deposition. There is no evidence for N-atom incorporation into the oxide layer itself. In contrast, for remote PECVD deposition of oxides onto nitrides, O-atoms react with the nitride, and form an oxy-nitride alloy interfacial region layer.
The Influence of Thermal Treatment on Defect Characteristics in Cz-Silicon Wafers Investigated by Positron Annihilation Spectroscopy
Authors: Mascher P. , Puff W. , Hahn S. , Cno K. H. , Lee B. Y.
Published: September 2012

Positron lifetime and Doppler-broadening experiments as well as Fourier-transform infrared spectroscopy (FTIR) were performed on a variety of six-inch Czochralski (CZ) silicon wafers. Measurements were done at 14 equidistant locations across the wafers which were cut from the seed-, middle-, and tail-sections of two boules grown at different pull-speeds.

In the as-grown wafers, the positron response consisted of components from small oxygen-related clusters and “perfect” bulk silicon only. Possible contributions from vacancy-type defects were at or just below the detection limit. After a two-step heat treatment (750°C/ 4 hrs + 1050°C/6 hrs in N2) FTIR showed that significant amounts of oxygen (4–8 ppma) had precipitated in wafers taken from the seed-sections of the boules but not in any of the other wafers. The positron data did not reflect this distinctive difference, however, both lifetime and Doppler-broadening results strongly indicate the creation of vacancy-type defects at concentrations in the 1016cm−3-range.
A Lifetime Study of Oxygen Agglomeration Induced Defects in Cz Silicon Crystal by Surface Photovoltage (SPV)
Authors: Mishra Kamal , Huber W. , Lagowski Jacek
Published: September 2012

In this study the effect of oxygen agglomeration on minority carrier diffusion length in as-grown p-CZ silicon has been studied in detail. Oxygen-related defects were found acting as minority carrier traps in p-CZ silicon. These defects are not found in either oxygen-free FZ silicon or in n-type CZ silicon samples. The traps have profound effect on low excitation level diffusion length values leading to an apparent lifetime decrease by as much as an order of magnitude. This effect can be eliminated by a steady state “bias light” superimposed on the chopped excitation light. The traps can be annihilated and re-generated by thermal treatments.

Our study has also revealed oxygen-induced recombination centers. Significant improvement in lifetime is realized in p-type CZ silicon after heat treatment between 550°C and 800°C.