Table of contents

The biennial international conference on Extended Defects in Semiconductors started in 1978 with a meeting in Hünfeld, Germany. Subsequent meetings rotated between Poland, France, Great Britain, Germany, Russia and Italy, culminating in EDS2004 in Chernogolovka, EDS2006 in Halle and EDS2008 in Poitiers. EDS2010 was held at the University of Sussex at Brighton, UK from September 19th to 24th. An extension of the tabulation of this history, which first appeared on the EDS2006 website, is given in the attached PDF. It is with sadness that we note one of the founders of the series, Prof. Dr Helmut Alexander, passed away on 3 December 2009 and we were proud to dedicate EDS2010 to his memory. It has become a tradition to make an award in his name, and this year it was made to Ivan Isacov for his poster "Electrical levels of dislocation networks in p- and n-type silicon". A short and warm celebration of Prof. Dr Alexander's life by his friends and colleagues, Prof. Drs Helmut Gottschalk, Eicke Weber and Wolfgang Schröter, is included in this volume.

The conference was a forum for the state-of-the-art of investigation and modelling of extended defects in semiconductors. Scientists from universities, research institutes and industry made contributions to a deeper understanding of extended defects, their interaction with point defects and their role in the development of semiconductor technology.

The remit of the conference included extended defects, nanostructures, nanoparticles, quantum dots and interfaces within semiconducting materials ranging from narrow to wide band gaps, including graphene-derived materials and diamond. Scientific interests range from defect geometry, electronic structure, dynamics, spectroscopy, microscopy, reactions and chemistry to introduction mechanisms, such as implantation and strained layers and the operation of devices such as integrated circuits, heterostructures, and solar cells.

The organisers were confronted with a long period between the afternoon outing to Arundel Castle and dinner in the evening at Wiston House, a mansion of Tudor origin near Steyning, West Sussex. So a short audience-participation seminar was held in the conference room of the manor, covering the history of dislocations and the history of the conference series. We were also able to extend the appreciation of the life of Prof. Yuri Ossipyan (15 Feb 1931 – 10 Sep 2008) briefly given at EDS2008.

EDS2010 continued the drive into graphene-based materials with a session devoted to them, and it gave immense pleasure to many of us who were his former students to dedicate a session to the work of Professor R Jones. We are grateful to his present and former co-workers who came and presented an impressive perspective on their work with him and a vision of a vigorous future for him in his retirement and for AIMPRO, the current Density Functional Theory code that derives from the one he established with his former student, Dr Patrick Briddon.

For EDS2010 we made two minor modifications to the appearance of the conference: a central webpage www.eds-conferences.org, ably managed by our webmaster, Dr Gemma Haffenden, and a Facebook page, "EDS conference series", which Dr Amy Gandy runs enthusiastically. Amongst other things the conference photographs appear here. "I like this". In fact, currently 22 FB-ers "like this" and I am sure it will grow.

Finally, it is a pleasure to acknowledge the significant contributions of Co-Chair, Prof. Marek Skowronski, Conference Manager, Dr Christopher Latham, and the editors of this volume, Drs Jon Goss and Chris Ewels, who in turn wish to thank Dr Alexis Vlandas for his help proof reading the articles.

We all wish the best of luck to Prof. Philomela Khomninou and her team in the organisation of EDS2012.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Helmut Alexander was one of the four initiators of the "International Symposium on Dislocations in Tetrahedrally Coordinated Semiconductors" (Hünfeld 1978). This conference was the beginning of a conference series which got its new name EDS (Extended Defects in Semiconductors) first in 1980. He who gave his name to the "Helmut Alexander Award" of the EDS conference died on the third of December, 2009. The international advisory committee of EDS honoured his scientific work in 2002 recognizing him by instituting an award for the best poster presentation for a young scientist at the running conference session. The authors try to review his life with some of his scientific highlights.

Recent theoretical investigations of the properties of dislocation cores in silicon are reviewed. New results, obtained from numerical simulations for the non-dissociated screw and 60° dislocations, are presented and discussed in relation with experiments.

Instrumented micro-indentations have been performed at room temperature on 4H-SiC homoepitaxial single crystals with different doping. For these experiments, it appears that the pop-in event occurs at the same level of load for intrinsic and n-type SiC and at a higher load level for p-type. Correlation of the pop-in event with dislocation nucleation indicates that doping acts on dislocation nucleation and that p-type doping plays a hardening role on the plastic behaviour of 4H-SiC. This result is confirmed by the conventional measurement of imprint size using scanning electron microscopy.

Transmission X-Ray topography (X-ray imaging) was used to characterize the density and type of the native dislocations in ZnO substrates. C-oriented ZnO bulk materials from different origins were compared, either high purity Chemical Vapor Transport (CVT) grown or commercial, hydrothermally grown wafers. Elongated dislocations lying within the substrate were found in hydrothermal substrates. In CVT crystals, the density of dislocations was found to be too high for X-ray determination of their Burgers vector. However, in hydrothermal crystals, the density of dislocations were found to be in the range < 10⁴ / cm² and extend mainly within the substrate. Whereas complete Burgers vector identification is not achieved, two kinds of dislocations have been evidenced : grown-in, swirled dislocations ("high" temperature) and linear, gliding dislocations, most probably developped during the cooling steps in (0 1–1 0) glide planes.

The laser scattering tomography technique enables the observation of non-decorated dislocations in Si crystals. In polarization and tomography measurements, changes in the dislocation scattering intensity are observed. A study of the light scattering by a dislocation was then developed and described in this paper. Based on theoretical results and experimental observations, slip system of a non-decorated mixed dislocation can be totally determined.

The effects of the speckle phenomenon on Makyoh-topography imaging is analysed. The speckle manifests itself as a quasiperiodic pattern in the Makyoh image which is easily mistaken for an image of a periodic surface morphology. The characteristic signature of speckles in Makyoh images is determined, thus allowing for its recognition. The effects of speckle on the Makyoh imaging is analysed as a function of surface roughness, illumination coherency and wavelength, light source size and instrumental parameters. It is shown that speckle effects are present even for incoherent illumination because of the coherency enhancement due to the limited source size. The findings are illustrated with experimental images of various semiconductor samples.

The (0001) surface of freestanding GaN and an (0001) oriented epitaxial GaN layer of 3 μm thickness on sapphire have been deformed at room temperature using a Vickers indenter. The samples were indented with two different orientations of the indenter with loads in the range from 0.02 to 4.90 N and 0.10 to 4.90 N, respectively. Dislocations and cracks at the indentations were observed by means of scanning electron microscopy, cathodo-luminescence, optical microscopy and transmission electron microscopy. Dislocations occur at all indentations for the loads used in the investigations. In both materials, the dislocation arrangement corresponds to the symmetry of the indented surface and the orientation of the indenter has only a marginal influence. Higher loads lead to radial cracks at the corners of the indentations and lateral cracks beneath the surface. The crack system is predominantly determined by the symmetry and orientation of the indenter. The dislocation arrangement and the crack system in freestanding GaN and an epitaxial layer of GaN on sapphire are compared.

We present a study of the dislocation network that occurs in the space charge region of a Schottky diode, by means of DLTS and our recently developed cathodoluminescent (CL) technique called Pulsed-CL. The details of the Pulsed-CL technique are provided. We establish a correspondence between the CL spectra of dislocation-related luminescence in silicon in the vicinity of the so-called D1 band and levels determined from DLTS measurements. The centres responsible for the 815 meV CL component are related to dislocations cores while the centres responsible for the 795 meV CL component are related to some defects outside of the dislocation cores.

The results of a theoretical calculation of the Pool-Frenkel effect due to the strain field of screw and 60° dislocations upon the valence band in silicon, and of a detailed DLTS study of the electrical field impact on carrier emission from the dislocation-related states of two types of bonded samples are presented and discussed. A good agreement between the theory and experiment was established. It is concluded that the large Pool-Frenkel coefficient value that significantly exceeds the value for a Coulomb-like potential is a new distinguishing feature of the hole thermo-emission from dislocation-related levels in silicon.

The results of deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) investigations on directly bonded n- and p-type silicon wafers with small twist misorientation angles ranging from 1 to 5 degrees are presented and discussed. Both shallow and deep levels in the upper half of a band gap are found and a good correspondence between the DLTS and MCTS data on n- and p-type samples was established. The dependence of DLTS-peak magnitude on twist and tilt misorientation angles (density of dislocations) was investigated and the origin of different levels is suggested.

Oxygen-related thermal donors (OTDs) in oxygen-enriched Czochralski Ge crystals grown from a melt fully covered by B₂O₃ liquid were investigated by infrared spectroscopy. Interstitially dissolved oxygen concentrations [O_i] and thermal donor concentrations N_TD in Ge specimens annealed at 350°C for 64h and at 550°C for 1h, followed by subsequent fast cooling to room temperature, were measured in comparison with those in as-grown Ge. By annealing at 350°C, an absorption peak developed at 780 cm⁻¹ and the peak height at 855 cm⁻¹ related to [O_i], decreased. The absorption coefficient at 780 cm⁻¹ showed the same correlation to the difference between the total concentration of oxygen atoms and the dissolved oxygen concentration in the annealed specimens. It was found that the number of oxygen atoms forming the OTD increases with increasing annealing time at 350°C.

The principal characteristic of nonpolar and semipolar heteroepitaxial interfaces is their anisotropy that leads to distinct ways of misfit accommodation along two in-plane directions. One direction can require misfit dislocations with out-of-plane Burgers vectors that induce epilayer tilts and low-angle grain boundaries, and the other necessitates the introduction of multiple basal-plane stacking faults. The reduced bicrystalline symmetry also favours the coexistence of distinct epilayer orientation relationships. This may result in nanocrystalline interfacial zones comprising low-energy grain boundaries that act as defect sources for the matrix epilayer, generating threading dislocations and stacking faults.

Light emitting structures with InGaN/GaN multiple quantum wells have been studied in the Electron Beam Induced Current (EBIC) mode of a scanning electron microscope (SEM). Special attention is paid to the channels of enhanced carrier transport across the active region demonstrating bright EBIC contrast. Defects with the smallest bright contrast are associated with threading dislocations while the large defects present in lower density could be associated with dislocation bunches. Low energy (10 keV) electron beam irradiation in the SEM was found to suppress the bright EBIC contrast of these defects. A comparison with the cathodoluminescence spectra changes due to similar exposure allows us to assume that recombination enhanced diffusion is responsible for the effects observed.

Al_xIn_1−xN films (0 ≤ x ≤ 1) have been sputter deposited and annealed, both without and with terbium co-doping, to obtain a series of matrices whose band gap energies span the range from around 2 eV to 6 eV. The terbium green luminescence spectra (excitation wavelength 230 nm, i.e. 5.4 eV) are measured at room temperature as a function of the aluminium content (band gap route) and of the terbium concentration (concentration route). The green luminescence assumes a maximum of the integrated intensity at a band gap energy of 4.1 eV (x = 0.7) which can be argued to result from a resonant energy transfer from the host matrix into the Tb luminescence centres. Furthermore, the dependence of this maximum integrated intensity as a function of the Tb concentration, i.e. of the average distance between the Tb centres, suggests the energy transfer from the host material into the Tb luminescent centres to be due to dipole-dipole interaction via an exciton bound to the centre.

To qualitatively determine the behaviour of micro-macro properties of a quantum dot grown in a non-polar direction, we propose a simple semi-classical model based on well established ideas. We take into account the following empirical phenomena: (i) The displacement and induced strain at heterojunctions; (ii) The electrostatic potential arising from piezoelectric and spontaneous polarisation; and (iii) The localisation of excitons (particle-hole pairs) arising from quantum confinement. After some algebraic manipulation used to cast the formalism into an arbitrarily rotated frame, a numerical model is developed for the case of a semi-polar wurtzite GaN quantum dot buried in a wurtzite AlN matrix. This scheme is found to provide a satisfying qualitative description of an isolated semi-polar quantum dot in a way that is accessible to further physical interpretation and quantification.

Co-doping of SiO₂ with Si and Er to achieve silica fibre amplifiers has resulted in encouraging levels of light emission, much above those of Er-only doped SiO₂. However, different fabrication methods, i.e., co-implantion and sequential implantation of Er and Si, has led to several factors difference in light levels. This paper looks into the reasons for these differences by establishing structure and local stoichiometry of the created entities via analytical transmission electron microscopy. In both cases Si-nanocrystals (NCs) have formed in the SiO₂ matrix. In the former case Er-ions are co-located with /integrated within the NCs, in the latter case NCs and Er are separate. By assessing the NCs' internal and interfacial structure with the surrounding material, we attempt to identify chemical/structural Er-phases/defects and their effect on the sensitising efficiency in the Er:Si-NCs system; high resolution phase contrast- and high angle dark field imaging as well as nano-scale spatially resolved electron energy core loss- and plasmon-spectroscopy carried out in an aberration corrected dedicated STEM lend valuable support to these studies.

The realization of defined dislocation networks by hydrophobic wafer bonding allows the characterization of electrical properties of individual dislocations. The present paper describes the fabrication and characterization of SOI MOFSETs with various dislocations densities in the Si channel. The aim was to investigate the electrical properties in samples containing only 6 dislocations. A drain current of I_D > 1×10⁻² A induced by a single dislocation was determined by data extrapolation from current measurements in combination with previously analyzed samples containing a varying dislocation density.

Yielding and twinning in bulk and nanocrystalline semiconductors are considered based on the activation of perfect or partial dislocation loops. Assuming that the yield stress of the crystal is proportional to the critical stress necessary for the activation of a perfect Frank-Read source, it is shown that for a range of crystal orientations with respect to the applied shear stress, the Hall-Petch relationship for a silicon polycrystal fails when the average grain diameter is of the order of 3 nm or less. It is further shown that, assuming the double-cross-slip mechanism of twin formation in silicon, twinning is easier than slip for a range of crystal orientations in nanocrystals.

SiC films grown by vapor phase reaction consist of multicrystalline grains. The size of grains depends on growth parameters, such as temperature and the relative concentration of the Si and C components. A small fraction of large grains demonstrate very efficient luminescence. Several techniques have been used to study the origin of the luminescence. Cathodoluminescence and photoluminescence revealed flat regions as sources of emission. Diffraction of back scattered electrons and X-ray analysis suggests that efficient emission is observed for grains with a small fraction of the rhombohedral phase. On the basis of the experimental data we assumed that the layers of rhombohedral phase or the interface between these layers and the host material are the origin of the luminescence.

Dislocation structures produced at room temperature under confining pressure (5 GPa) have been investigated by transmission electron microscopy and photoluminescence. Following annealing treatments in the temperature range 300°C – 600°C the initial DRL spectrum changes to a well-known spectrum of dislocation luminescence of dissociated glide set dislocations. In spite of the fact that no transformation of perfect shuffle dislocations to dissociated glide ones was observed by transmission electron microscopy, experimental photoluminescence data analysis does not exclude the possibility either of such transformation or nucleation of glide dislocations following annealing treatments at temperature as low as 300°C.

We analyze the band to band radiative transitions in germanium thin films deposited on silicon and compare them with those in bulk material. A significant down shift of the direct transition related peak was observed from the thin films samples, caused by the preparation formed tensile strain in the film. A comparison between the ratios of the direct to indirect transitions peak intensities showed that those are very similar for the thin films and the bulk material, when the self absorption of the emission is accounted for. The observed similarity in the spectral shape indicates that the strong direct transition luminescence detected in strained germanium films is mainly due to the improved light extraction in the energy range of about 0.8 eV, rather than an increase in the probability of band to band direct transition. We find a feature at around 0.72 eV in the spectrum of the germanium luminescence, which correlates with the presence of dislocations in the crystal. We discuss the origin of this feature in view of one dimensional dislocation bands, split off from the Gamma valley of the conduction band due to the dislocations local strain field.

The phenomena of interaction and propagation of cracks under the contribution of hydrogen were studied in (001) silicon substrate in which an array of scattered over-pressurized He-plates was previously introduced at a given depth. Their propagation under subcritical regime was activated through diffusional supply of H atoms introduced by implantation/annealing. Interactions between the tips of non coplanar cracks take place in a nanometric scale; they can be of plastic-type leading to the formation of extended defects or of elastic-type resulting in deviations of crack-tip propagation. While the planar interactions facilitate the propagation of cracks, those of non coplanar-type stop them. The observations were carried out by transmission electron microscopy and the results were discussed and modelled by using concepts of elasticity and fracture mechanics.

Homoepitaxially grown single crystal CVD diamond has a dislocation arrangement not seen in natural IIa diamond. Whereas in the latter, dislocations lie on (111) planes along [10] directions, dislocations in CVD diamond lie nearly along the [001] growth axis and are arranged in bundles with almost four fold rotational symmetry. Their large strain is easily seen in birefringence and we model the arrangements in the bundle to account for the singular behaviour of the birefringence when the polarisers are rotated with respect to the crystal. The optical absorption spectrum of brown CVD diamond displays a continuum similar to that found in brown IIa natural diamonds but in addition broad point defect induced bands. We investigate the suggestion that the 2.38 eV (560 nm) peak is related to VNH. We suggest that the breadth of these bands is related to the large structural change when the defect is excited.

The link between brown colour and vacancy structures in natural diamond and has been studied through the techniques of aberration corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). Bright field (BF) and high angle annular dark field (HAADF) STEM imaging modes have revealed discrete patches of stronger contrast, of the order of 1nm in size, that are similar to simulated images of vacancy clusters. Core loss spectra show a pre-edge feature for brown diamond corresponding to π* states. This feature is absent for colourless and heat treated brown diamonds. Additional spectra acquired in regions containing dislocations for both brown and white (colourless) diamonds showed a second pre-edge feature indicating that dislocations have electronic states associated with them and are therefore optically active.

The mechanism of dislocation dipole annihilation has been investigated in C and Si using atomistic calculations with the aim of studying their annihilation by-products. It is shown, in C as well as in Si, that dipole annihilation yields debris that can be depicted as a cluster of vacancies, or alternately by two internal free surfaces. These defects have no strain field and can hardly be seen using usual TEM techniques. This suggests that the brown colouration of diamond could be due to microstructures resulting from deformation mechanisms associated with dipole formation and their annihilation rather than to a climb mechanism and vacancy aggregation. In silicon where a number of dipoles have been evidenced by TEM when dislocation trails are found, such debris could be the missing link responsible for the observation of strong chemical reactivity and electrical activity in the wake of moving dislocations.

Single crystal CVD synthetic diamond samples grown on substrates close to (001) have been studied using X-ray topography, photoluminescence imaging and Nomarski microscopy. The substrates used for this study were polished up to 15 degrees from (001). Nomarski images of the final growth surface have been compared with X-ray section topographs and photoluminescence images, both sampling a plane close to the surface of a (010) cross-sectional slice. The photoluminescence images provide evidence of the direction of step flow growth which was compared with the surface morphology. Samples grown on substrates polished off-(001) about [010] by greater than 10 degrees exhibit regions possessing both [001] and [101] dislocations as a result of on-axis and off-axis step flow growth respectively. Our previously published model suggests relatively low angle surface inclinations arising from risers are needed to switch dislocation direction from [001] to [101] line direction, and core energies per unit length suggest a minimum riser angle of 10 degrees is required. Samples grown on substrates polished greater than 10 degrees from (001) exhibit dislocations with a [101] line direction consistent with the model. Below this angle the dislocations do not switch line direction. Possible mechanisms influencing dislocation line direction via off-axis growth are discussed.

The properties of phosphorus-related defects in freestanding silicon nanocrystals with different surface compositions are investigated using density functional theory models. Both hydrogen (H-) and hydroxyl (OH-) covered surfaces are considered. The dependence of the formation energy of substitutional phosphorus on the distance to the surface is found to be stronger in hydroxyl-covered crystals. The formation of tricoordinated defects, energetically favourable in hydrogenated nanocrystals, is less likely in nanocrystals with hydroxylated surfaces. Further, the ionisation energy level of P-doped nanocrystals is found to be deeper in OH-covered nanocrystals than in H-covered nanocrystals.

With recent developments in advanced materials and nanostructures, particularly those designed for electronics, it is evident that their successful application will depend not only on their electrical properties, but also on their mechanical characteristics. Nanoindentation is a unique method for examining nanostructured materials, as it requires a small volume of the solid and probes the surface layers of particular interest. Nanoindentation of bulk semiconductor crystal structure has been frequently used to study the onset of irreversible deformation – incipient plasticity. Here we present recent experiments supported by molecular dynamics simulations that allow determination of the origin of incipient plasticity in GaAs crystals. It will be demonstrated that, as in case of silicon, plastic deformation of GaAs starts from a pressure-induced structural phase transformation.

In this study n- and p-type polished Czochralski-grown Si (Cz-Si) and p-type polished and as-cut multi-crystalline (mc) Si wafers have been directly H plasma treated in a plasma enhanced chemical vapour system in order to study H subsurface defect formation. Raman spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy and transmission electron microscopy have been used to characterise the samples. In polished Cz-Si wafers, H induced defects were only observed up to 1 μm below the surface [1,2], while in similarly treated mc samples H induced defects were observed on grain boundaries and dislocations up to several μm below the surface [3]. It is also established that the distribution of H in the subsurface regions of the Cz-Si substrates after hydrogenation as well as the formation of structural defects depend on the type of doping. Evolution of Si-H_x bonds in hydrogenated Cz Si samples starts at 400 °C, while evolution of H initiated structural defects starts at 600 °C, when SiH_x bonds are mostly dissolved.

Dilute magnetic semiconductors based on transition metal doped silicon have attracted intense interest in recent years due to their compatibility with current silicon technology. Here we present transmission electron microscopy, secondary ion mass spectrometry and ferromagnetic resonance studies of silicon implanted with 1×10¹⁶ ions/cm² of Mn ions and silicon co-implanted with both 1×10¹⁶ ions/cm² of Mn ions and 2×10¹⁶ ions/cm² of carbon ions at a substrate temperature of 350 °C. Afterward, the samples were annealed at temperatures between 800 and 1000°C. The SIMS results show a marked difference between the two specimens while the TEM results show similar features in terms of Mn precipitation and particle evolution. The carbon implanted specimens show additional features that appear to be amorphous silicon pockets within the crystalline implant region. Only one specimen (Mn only implant, unannealed) showed any ferromagnetic properties.

We present results of secondary ion mass-spectrometry and Rutherford backscattering spectroscopy of the Zn implantation profile in the damaged layer of a n-type Cz-Si(100) substrate, as well as the profile change during annealing. Si wafers were implanted with ⁶⁴Zn⁺ ions at energy of 100keV and ion dose of 2×10¹⁴cm⁻². They were then subsequently annealed at 400°C for 60min and 700°C for 10min. Analysis of experimental data shows that in the as-implanted sample on a silicon surface a damage gauzy amorphous layer with thickness about 80nm was created, located inside the substrate at the ion-implantation depth. After two annealing steps the defects were completely annealed out. From the Zn depth profiles we observe that during annealing the Zn concentration decreases and the Zn peak concentration moves to the wafer surface. The Zn concentration maximum exceeds the solubility limit of Zn in Si, suggesting decomposition of Zn solid solution in Si and Zn precipitation.