bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infrared Photoconductivity and Photoluminescence from InAs/Ga1–xInxSb Strained-Layer Superlattices
Authors: Miles R. H. , Chow D. H. , Mcgill T. C. 
Published: March 2011

ABSTRACTWe have examined spectrally resolved photoconductivity and photoluminescence from InAs/Ga1–xInxSb strained-layer superlattices, which have been proposed as infrared detectors in the 8-14 μm region. Our measurements indicate that the energy gaps of the strained–layer superlattices are substantially smaller than those of InAs/GaSb superlattices with similar layer thicknesses, in agreement with previous theoretical predictions. Measurements on InAs/Ga1–xInxSb superlattices with x=0 and 0.25 and layer thicknesses of 25 – 45 A indicate superlattice band gaps of 3 – 15 μm, in excellent agreement with gaps calculated by a two band k · p model. Our results demonstrate that far-infrared energy gaps are compatible with the thin layers necessary for strong optical absorption in type-IT superlattices, and suggest that InAs/Ga1–xInxSb superlattices are promising candidates for far-infrared detection.
Zinc Diffusion in GaAs-AIGaAs Heterojunction Bipolar Transistor Structures
Authors: Hobson W. S. , Pearton S. J. , Jordan A. S. 
Published: March 2011

ABSTRACTWe have examined the diffusion of Zn from the base of GaAs-AIGaAs heterojunction bipolar transistor (HBT) structures during growth by organometallic vapor phase epitaxy. The role of Si doping in the emitter-contact, emitter, and collector/subcollector in enhancing the Zn diffusion has been determined by separately doping each layer. For a growth temperature of 675°C Zn shows no observable redistribution up to concentrations of 3x1019 cm−3 without Si doping. The addition of Si to the adjacent AIGaAs emitter and GaAs collector/subcollector layers causes significant diffusion from the base, while Si doping of the GaAs emitter-contact results in even greater Zn redistribution. Silicon counter-doping in the base region retards the Zn diffusion. These results are consistent with a recent model which shows that the n-type surface layer enhances the formation of gallium interstitials which diffuse into the structure and displace the Zn in the base via a kick-out mechanism.
Scanning Tunneling Microscopy Studies of GaAs Heteroepitaxial Growth on Si
Authors: Biegelsen D. K. , Bringans R. D. , Northrup J. E. , Swartz L. E. 
Published: March 2011

ABSTRACTWe discuss the benefits and limitations of scanning tunneling microscopy (STM) for use in studies of the early stages of heteroepitaxy. We describe a system merging in vacuo an MBE, STM, XPS, LEED, etc. We present results for the initial stages of GaAs growth on vicinal Si(100), including As termination, Ga capping and subsequent 2D and 3D competition.
Tem Study of the Structure of Mbe GaAs Layers Grown at Low Temperature
Authors: Liliental-Weber Zuzanna 
Published: March 2011

ABSTRACTThe structural quality of GaAs layers grown at 200°C by molecular beam epitaxy (MBE) was investigated by transmission electron microscopy (TEM). We found that a high crystalline perfection can be achieved in the layers grown at this low temperature for thickness up to 3 μm. In some samples we observed pyramid-shaped defects with polycrystalline cores surrounded by microtwins, stacking faults and dislocations. The size of these cores increased as the growth temperature was decreased and as the layer thickness was increased. The upper surface of layers with pyramidal defects became polycrystalline at a critical thickness of the order of 3μm. We suggested that the low-temperature GaAs becomes polycrystalline at a critical thickness either because of a decrease in substrate temperature during growth or because strain induced by excess As incorporated in these layers leads to the formation of misoriented GaAs nuclei, thereby initiating polycrystalline growth. The pyramidal shape of the defects results from a growth-rate hierarchy of the low index planes in GaAs.
Characterization of GaAs/AlGaAs Heterostructure Quantum Wells by Microwave Absorption
Authors: Zappe Hans P. , Jantz Wolfgang 
Published: March 2011

ABSTRACTMagnetic-field-dependent microwave absorption Is shown to be a useful non-destructive and contact-free technique to study transport behavior in GaAs/AlGaAs devices. It allows quick measurement of resistance, mobility and carrier concentration in the two-dimensional electron gas of heterostructure quantum wells. The two and three dimensional conductivities may be separately evaluated allowing detailed study of conduction in the active layer of high electron mobility (HENT) devices. Applications of the approach to examination of device structural dependencies, carrier-density conduction behavior and the effects of etch processing on quantum well integrity are presented.
High Quality GaAs on Si by Selective Area Epitaxy
Authors: Karam N.H. , Haven V. , Vernon S.M. , El-Masry N. , Lingunis M. , Haegel N. 
Published: March 2011

ABSTRACTSelective area Epitaxy (SE) of high quality GaAs on Si films has been achieved using conventional MOCVD and Atomic Layer Epitaxy (ALE) nucleation techniques. Epitaxial GaAs films were deposited inside windows etch patterned in the oxide coated Si wafers. SE was found to eliminate wafer warpage, reduce film cracking and reduce the tensile stresses for islands less than 200 µm/side. Complete stress relief has been achieved in 10 µm/side islands after oxide removal. Defect reduction techniques have been employed resulting in two orders of magnitude reduction in the dislocation density and excellent surface morphologies. This paper addresses the potential of SE, by the above techniques in improving the quality of the GaAs on Si films.
Mbe Growth and Characterization of Hgcdte Heterostructures
Authors: Koestner R.J. , Goodwin M.W. , Schaake H.F. 
Published: March 2011

ABSTRACTHgCdTe heterostructures consisting of a thin n-type widegap (250 meV or 5 μm cutoff) layer deposited on an n-type narrowgap (100-125 meV or 10-13 μm cutoff) layer offer the promise of very high performance metal-insulator-semiconductor (MIS) photocapacitors for long wavelength infrared (LWIR) detection. Molecular Beam Epitaxy (MBE) is a candidate growth technology for these two layer films due to its fine control in composition, thickness and doping concentration. The critical materials issues are reducing the defect content associated with twins in the grown layers, achieving low net donor concentrations in the widegap layer, and avoiding the formation of misfit dislocations at the HgCdTe heterointerface. This paper will report on our recent progress in these directions.
Explanation of Observed P-Type Conductivity in Movpe ZnSE/GaAs Heterostructures
Authors: Briot O. , Cloitre T. , Tempier N. , Sauvezon R. , Averous M. , Aulombard R.L. 
Published: March 2011

ABSTRACTTogether with the advanced growth technologies of zinc selenide epitaxial films by MOVPE or MBE, severals workers have reported the observation of p-type conductivity in this material. However, there are some inconsistencies in most of the papers reporting such results.We report here the MOVPE crystal growth of nominaly undoped ZnSe/GaAs S.I. layers using alkyls as precursors, and their optical and electrical characterizations. We show the possibility to observe p-type conductivity in ZnSe due to a hole accumulation at the interface in the GaAs side. This is consistent with a simple model taking Into account the conduction and valence bands discontinuities at the ZnSe/GaAs interface.
Optical Investigation of the Band Offset of CdxZn1−xTe /ZnTe and ZnSexTe1−x/ZnTe Superlattices
Authors: Rajakarunanayake Y. , Phillips M. C. , Mccaldin J. O. , Chow D. H. , Collins D. A. , Mcgill T. C. 
Published: March 2011

ABSTRACTWe have analyzed photoluminescence spectra from CdxZnl−xTe /ZnTe and ZnSexTel−x/ZnTe strained layer superlattices grown by MBE, and obtained the band offsets by fitting to theory. We find that the valence band offset of the CdTe/ZnTe system is quite small (-50± 160 meV). In CdxZnl−xTe /ZnTe superlattices, the electrons and heavy holes are confined in the CdxZn1−xTe layers (type I), while the light holes are confined in the ZnTe layers (type II). On the other hand, the photoluminescence data from the ZnSexTe1−x /ZnTe superlattices suggest that the band alignment is type II, with a large valence band offset (−907 ± 120 meV). We also investigated the band bowing in the ZnSexTel−x alloys by optical spectroscopy, and found that there is only a small component of bowing in the valence band, while most of the bowing occurs in the conduction band. Based on our results for band alignments, we evaluate the prospects for minority carrier injection in wide bandgap heterostructures based on ZnSe, ZnTe, and CdTe.
Growth and Characterization of Znsete Epilayers and Superlattices
Authors: Phillips M. C. , Rajakarunanayake Y. , Mccaldin J. O. , Miles R. H. , Chow D. H. , Collins D. A. , Mcgill T. C. 
Published: March 2011

ABSTRACTLittle has been published about Te-rich ZnSexTel−x grown at low temperatures, in spite of some successes in the fabrication of wide band gap light emitting devices from ZnSeTe alloys grown at higher temperatures. We present x-ray diffraction and photoluminescence (PL) spectra for ZnSeTe epilayers and ZnSeTe/ZnTe superlattices grown by molecular beam epitaxy (MBE). These we compare with measurements on ZnTe, ZnSe and CdZnTe epilayers and on CdZnTe/ZnTe superlattices grown under similar conditions and also with data published for ZnSeTe alloys grown at high temperatures. Equilibrium phase diagrams for the ZnSeTe alloy system suggest a large miscibility gap at MBE growth temperatures; this may account for some unusual features in the (PL) spectra and for large line widths in the x-ray data. In spite of these possible miscibility problems, we find that ZnSeTe alloys luminesce brightly.
Xps and Aes Studies of the Initial Stage of CdTe Growth on (100) GaAs by Movpe
Authors: Ekawa Mitsuru , Yasuda Kazuhito , Sone Syuji , Sugiura Yoshiyuki , Saji Manabu , Tanaka Akikazu 
Published: March 2011

ABSTRACTXPS and AES analyses were performed to investigate the initial growth mechanism and the selection of the growth orientations of CdTe layers grown on (100) GaAs substrates by MOVPE. The (100) CdTe growth was reproducibly achieved when the GaAs surface was completely covered by one monolayer of Te before the growth, otherwise (111) growth occurred.
Properties of IV-VI Narrow Gap Semiconductors on Fluoride Covered Silicon
Authors: Zogg H. , Maissen C. , Blunier S. , Masek J. , Meyer V. , Pixley R.E. 
Published: March 2011

ABSTRACTWe present new results on structural and electronic properties of epitaxial lead chalcogenides on Si-substrates. A stacked MBE-grown CaF2/BaF2 buffer of 200 nm thickness serves to overcome the large lattice- and thermal expansion mismatches. Lead chalcogenide layers are grown by MBE or HWE with thicknesses of a few μm.The X-ray rocking curve widths of these layers are below 200 arc sec. They are as low as curve widths of similar layers grown on bulk BaF2, or GaAs layers of comparable thicknesses on Si. The mechanical strain-state of the layers was determined with x-ray measurements and RBS channelling angular scans. Strain is below 4.10−4 at room temperature, indicating a near complete relaxation of the thermal and lattice misfit induced strains.The quality of the layers is sufficient to integrate whole photovoltaic IR-sensor arrays.We have fabricated linear arrays with cut-off wavelengths of 12 μm by using Pb1−xSnxSe, 5 μm with PbTe, and 3 - 4 gm with PbS and Pb1−xEuxSe. The structures withstand repeated cooling to the 80K operation temperature.
Disilane Adsorption on Ge(111): A Multiple Internal Reflection Infrared Spectroscopy Study
Authors: Crowell John E. , Lu Guangquan 
Published: March 2011

ABSTRACTThe adsorption and decomposition of disilane on the Ge(111) surface has been investigated using multiple internal reflection infrared spectroscopy (MIRIRS). At temperatures ≤ 110 K, Si2H6 weakly bonds to the Ge surface in a molecular fashion. Upon mild heating to temperatures between 110 - 150 K, both desorption and dissociation occur. Dissociative adsorption also occurs upon exposure at temperatures > 110 K. Molecular adsorption is no longer observed for exposure at temperatures above 150 K. Detection of the low frequency deformation modes provides direct evidence for dissociation of the Si-Si bond between 120 - 150 K. The primary species present at 150 K is silyl, SiH3. Si-H bond scission takes place from 150 - 500 K, resulting in GeH formation. Production of SiH2 and SiH is spectroscopically identified in this temperature range.
Epitaxial Growth and Stability of C49 TiSi2 ON Si(111).
Authors: Jeon Hyeongtag , Honeycutt J. W. , Sukow C. A. , Humphreys T. P. , Nemanich R. J. , Rozgonyi G. A. 
Published: March 2011

ABSTRACTEpitaxial TiSi2 films have been grown by molecular beam epitaxy (MBE) on atomically clean Si(111)-orientated substrates. The growth procedure involves the ambient temperature deposition of Ti films of 50Å thickness and annealing to 800°C. In situ low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) techniques have been used to monitor the TiSi2 formation process. The epitaxial films have been identified as the C49 metastable phase by both Raman spectroscopy and electron diffraction. Plan view transmission electron microscopy shows three different connected island morphologies. The individual island structures are single crystal and are grown epitaxially with different crystallographic orientations. The orientational relationship of the largest islands is given by [3 1 1] C49 TiSi2//[112]Si and (130) C49 TiSi2//(l1 1)Si. High resolution transmission electron microscopy (HRTEM) cross-section shows a coherent interface extending over several hundred angstroms.
Specimen Preparation of Thin Crystalline Fibers for Transmission Electron Microscopy
Authors: Koch Rosemarie , Marshall Ann F. 
Published: March 2011

ABSTRACTA technique was developed to prepare crystalline fibers of less than 1 mm diameter for transmission electron microscopy. Cross sections were made by casting a short piece of the fiber in an epoxy resin, sectioning the block, and laminating the slices against thin glass discs for stability before dimpling. Longitudinal sections were reinforced in a similar manner. TEM tungsten rings were sometimes used as an alternative method to add stability to the longitudinal sections. The technique was especially developed for Bi-Sr-Ca-Cu-O compounds but is also suitable for other materials.
Preparation of TEM Specimens of Rubber Modified Polymeric Materials by Ultramicrotomy and OsO4 Staining
Authors: Yegnasubramanian S. 
Published: March 2011

ABSTRACTThis paper presents the specimen preparation approaches developed to image rubber(butadiene) - modified epoxy polymeric materials used in the microelectronics industry by TEM. The methodology is complicated by the fact that silica and calcium carbonate (>75 wt%) are used as filler materials while the rubber is used as a toughening agent in the samples investigated.
Cross-Sectional TEM Specimen Preparation of Semiconductor Devices by Focused Ion Beam Etching
Authors: Park Kyung-ho 
Published: March 2011

ABSTRACTA procedure for preparing cross-sectional TEM specimens by focused ion beam etching (FIB) of specific regions on an integrated circuit chip is outlined. The investigation of the morphology, structure and local chemistry of precisely selected regions of semiconductor devices becomes increasingly important since the lateral dimensions and layer thickness of device structures are continually being reduced. The standard technique of preparing specimens for TEM, whether planar or cross-sectional, cannot select particular small regions. Some techniques and a number of tools and fixtures have been proposed which allow us to prepare TEM specimen of prespecified locations in complex devices. Most of these techniques, however, are still very difficult, tedious process and time consuming.A new technique has been proposed recently involving the use of FIB. The technique ensures that the preselected area of submicron scale will be located in the electron transparent section used for TEM imaging, in preparation turn-around time of about two hours. The TEM imaging of specific contacts via hole in a VLSI chip is illustrated.
Preparation of Planar and Cross-Sectional Thin Specimens by Chemical Dimpling with Optically Controlled Terminator
Authors: Hwang D. M. , Nazar L. , Chen C. Y. 
Published: March 2011

ABSTRACTWe have modified a conventional dimpling machine to perform chemical polishing with a reactive etchant. The modified dimpler also detects specimen perforation in situ optically, and automatically stops the dimpling process by lifting the dimpler wheel and flooding the specimen with a rinse solution. Using this apparatus, we are able to prepare both planar and cross-sectional thin specimens of compound semiconductor materials without using expensive and time-consuming ion-milling. The specimens have large thin areas, are free of artifacts, and are suitable for high-resolution lattice imaging.
Electron Paramagnetic Resonance in Semiconductors
Authors: Corbett James W. , Kleinhenz Richard L. , Wilsey Neal D. 
Published: March 2011

ABSTRACTThe use of electron paramagnetic resonance (EPR) in the study of defects in semiconductors is briefly reviewed, including group IV (C-diamond, Si, Ge, SiC), III-V (AlSb, GaAs, GaSb, GaP, InAs, InP, InSb), II-VI (BaO, BaS, BeO, CaO, CaS, CaSe, CdO, CdS, CdSe, CdTe, MgO, SrO, SrS, ZnO, ZnS, ZnSe, ZnTe) and miscellaneous svstems. The identification of defects via EPR is described as is the exploitation of that identification as a tool in future studies. Particular attention is paid to Si, where is emerging an integrated panorama of identified defects ranging from point defects to aggregates through intermediate defect configurations (as discussed by Tan) to dislocations and stacking faults; EPR results in Si as a testing ground for the theory of shallow donors, in the understanding of diffusion at high temperatures and in the study of heat-treatment defects are discussed as examples of the use of EPR as a tool in defect studies.
Undissociated Dislocations and Intermediate Defects in as+ Ion Damaged Silicon
Authors: Foell H. , Tan T. Y. , Krakow W. 
Published: March 2011

ABSTRACTUndissociated dislocation dipoles and intermediate defects are detected in As+ ion damaged Si using the lattice resolution technique of transmission electron microscopy. The present results are consistent with our proposed dislocation nucleation models.
Negative-U Properties for Point Defects in Silicon
Authors: Watkins G. D. 
Published: March 2011

ABSTRACTA defect has negative-U properties if it can trap two electrons (or holes) with the second bound more strongly than the first. It is as if there were a net attraction between the two carriers (negative Hubbard correlation energy U) at the defect, and the defect energy levels in the gap are therefore inverted from their normal order. Experimental evidence is presented that interstitial boron and the lattice vacancy, both common simple point defects produced by electron irradiation of silicon, have this unusual property. These defects represent the first and only concrete examples of negative-U centers in any material and serve as models for an understanding of the phenomenon.
Electronic and Mechanical Properties of Dislocations in Semiconductors
Authors: Hirsch P B 
Published: March 2011

ABSTRACTIt has been known for some time that the velocity of dislocations in semiconductors depends strongly on the concentration of electrically active impurities. Various explanations based on different models of the electronic structure of the dislocations have been proposed; they involve the dependence of the formation energy and/or activation energy of migration of dislocation kinks on the Fermi level. A review will be presented of these theories and of recent structural models of dislocation cores and kinks.
Characterization of Dislocations and Interfaces in Semiconductors by High Resolution Electron Microscopy
Authors: Spence J.C.H. , Olsen A. 
Published: March 2011

ABSTRACTIt is not presently possible to resolve the individual atoms in any semiconductor by high resolution electron microscopy (HREM). However symmetry arguments may be used to allow near-atomic resolution lattice images to be interpreted in rare favorable cases. This method is applied to the problem of distinguishing shuffle and glide set partial dislocations in silicon. It is also proposed that two dimensional characteristic loss energy selected diffraction patterns be used to reveal the local symmetry about selected substitutional species implanted in semiconductor lattices.
Defect Structure of the Epitaxial Pd2 Si-Silicon Interface
Authors: Cherns D. , Smith D.A. 
Published: March 2011

ABSTRACTThe crystallography of the epitaxial Pd2 Si-silicon interface has been analyzed with special reference to the character of interfacial dislocations. It is proposed that the Pd2 Si which forms at the interface does so by the diffusion stimulated glide of transformation dislocations.
From the Mystery to the Understanding of the Self-Interstitials in Silicon
Authors: Frank W. , Seeger A. , Gösele U. 
Published: March 2011

ABSTRACTOur present knowledge on self-interstitials in silicon and the rôle these defects play under widely different experimental conditions are surveyed. In particular, the following phenomena involving self-interstitials either in supersaturations or under high-temperature thermal-equilibrium conditions are considered: mobility-enhanced diffusion of self-interstitials below liquid-helium temperature, thermally activated diffusion of self-interstitials at inter-mediate temperatures (14O K to 600 K), concentration-enhanced diffusion of Group-III or Group-V elements in silicon at higher temperatures, and— as examples for high-temperature equilibrium phenomena — self-diffusion and diffusion of gold in silicon. This leads to the picture that the self-interstitials in silicon may occur in different electrical charge states and possess dumbbell configurations or are extended over several atomic volumes at intermediate or high temperatures, respectively.
The Effect of Annealing Temperature on the Morphology of Stacking Faults in Czochralski Silicon
Authors: Pinizzotto R. F. , Schaake H. F. 
Published: March 2011

ABSTRACTNucleation and growth of stacking faults formed in CZ silicon during oxygen precipitation have been studied using x-ray topography, TEM and FTIR. Samples were annealed in argon for various times at 550°C and 750°C followed by a 16 hour anneal in dry oxygen at 1000°C. In samples annealed at 550°C, the stacking faults were several layers thick with colonies of precipitates at their centers. The faults in samples annealed at 750°C contained only one particle and were single in nature. It is proposed that the faults are formed by thin oxygen precipitate platelets and that the different morphologies are due to different oxygen precipitation rates. The platelets are probably a modified cristobalite, as determined by micro-diffraction results.
Electron Microscope Characterization of Pulse Annealed Semiconductors
Authors: CULLIS A. G. 
Published: March 2011

ABSTRACTThe pulse processing techniques that have assumed prominence over the past few years offer various important advantages for device fabrication technology. However, the usefulness of each individual method depends substantially upon the specific annealing mechanism involved. This article demonstrates the role of electron microscopy in elucidating such mechanisms and in analysing annealed semiconductor structures of importance to both research workers and semiconductor technologists. The range of laser and electron beam pulse annealing methods is covered and defect structure transitions observed are related to the solid and liquid phase processes occurring. Characteristic impurity trapping and segregation phenomena are described.