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Full-Text Articles in Physical Sciences and Mathematics

Taxonomic And Paelogeographic Approaches To The Dasyclad Algae In The Upper Jurassic (Kimmeridgian)-Upper Cretaceous (Cenomanian) Peritidal Carbonates Of The Fele (Yassıbel) Area (Western Taurides, Turkey), İsmai̇l Ömer Yilmaz Jan 1999

Taxonomic And Paelogeographic Approaches To The Dasyclad Algae In The Upper Jurassic (Kimmeridgian)-Upper Cretaceous (Cenomanian) Peritidal Carbonates Of The Fele (Yassıbel) Area (Western Taurides, Turkey), İsmai̇l Ömer Yilmaz

Turkish Journal of Earth Sciences

In the Fele (Yassıbel) area in the north of Beyşehir Lake in the Western Taurides, Upper Jurassic (Kimmeridgian) - Upper Cretaceous (Cenomanian) peritidal carbonates were studied in detail. In this study, 30 species of dasyclad algae were identified and 3 new Salpingoporella species were identified within the peritidal carbonates. It was determined that they belong to 13 different genera: Acroporella, Actinoporella, Campbelliella, Clypeina, Cylindroporella, Epimastopora, Epimastoporella, Kopetdagaria, Macroporella, Otternstella, Rajkaella, Salpingoporella, and Selliporella. Salpingoporella is the dominant genus. Some of the species are new records for Turkey: Clypeina nigra, Clypeina parasolkani, Otternstella lemmensis, Salpingoporella biokovensis, Salpingoporella circassa, Salpingoporella piriniae, and …


Clinopyroxene Compositions Of The Isotropic Gabbros From The Sarıkaraman Ophiolite: New Evidence On Supra-Subduction Zone Type Magma Genesis In Central Anatolia, Kenan M. Yaliniz, M. Cemal Göncüoğlu Jan 1999

Clinopyroxene Compositions Of The Isotropic Gabbros From The Sarıkaraman Ophiolite: New Evidence On Supra-Subduction Zone Type Magma Genesis In Central Anatolia, Kenan M. Yaliniz, M. Cemal Göncüoğlu

Turkish Journal of Earth Sciences

The Sarıkaraman Ophiolite is one of the least dismembered ophiolitic units of the allochthonous Central Anatolian Ophiolites, which retains its recognizable pseudostratigraphy. The Sarıkaraman Ophiolite is represented in its lowermost part by isotropic gabbros. Within the isotropic gabbro sequence, clinopyroxenes are observed as small, colorless relicts with a cloudy appearance. In most of the samples, they are completely replaced by a successive generation of green to brown amphiboles. Clinopyroxenes display diopsitic to augitic compositions within the range of En 45 Fs 5 Wo 49 to En 50 Fs 9 Wo 41 . They are Ca-rich and Na-poor (Na 2 O


Field, Petrographic And Geochemical Features Of The Baranadağ Quartz Monzonite Of The Central Anatolian Granitoids, Turkey, Nurdan S. Aydin, A. Piril Önen Jan 1999

Field, Petrographic And Geochemical Features Of The Baranadağ Quartz Monzonite Of The Central Anatolian Granitoids, Turkey, Nurdan S. Aydin, A. Piril Önen

Turkish Journal of Earth Sciences

The Baranadağ quartz monzonite is one of the granitioid intrusions of the Central Anatolian Crystalline Complex (CACC) which represents the passive continental margin of the Anatolide-Tauride platform. Medium to coarse-grained Baranadağ quartz monzonites typically include mafic microgranular enclaves and K-feldspar megacrysts and are cut by aplitic dykes representing the youngest magmatic activity of the study area. The intrusion is mainly composed of orthoclase, plagioclase, quartz, hornblende, biotite and clinopyroxene. It displays a slightly alkaline character and relatively well-developed calc-alkaline trend. The metaluminous Baranadağ quartz monzonites show comparable field, petrographic and/or geochemical features with those of the H-type (Hybrid) granitoids of …


Biostratigraphic And Environmental Analysis Of The Upper Jurassic- Lower Cretaceous Carbonate Sequence In The Başoba Yayla Area (Trabzon, Ne Turkey), Kemal Tasli, Erol Özer, Cemi̇l Yilmaz Jan 1999

Biostratigraphic And Environmental Analysis Of The Upper Jurassic- Lower Cretaceous Carbonate Sequence In The Başoba Yayla Area (Trabzon, Ne Turkey), Kemal Tasli, Erol Özer, Cemi̇l Yilmaz

Turkish Journal of Earth Sciences

In the Başoba Yayla (Trabzon, NE Turkey) area, which is located in the Eastern Pontides northern zone, platform carbonates were deposited during the Late Jurassic-Early Cretaceous time in environments varying from intertidal/ supratidal to outer shelf. The carbonate sequence begins with a thick dolomite unit of the Late Jurassic to Early Cretaceous age. The following unit is rich in benthic foraminifers and pelecypoda shells. The foraminiferal assemblage comprising Vercorsella laurentii/camposaurii and Pseudolituonella gavonensis indicates a Late Hauterivian to Early Aptian age for this unit. The Late Aptian-Albian facies is characterized by bioclastic wackestones containing benthic foraminifers typical of outer platform …


Mafic Microgranular Enclaves In The Kozak Granodiorite, Western Anatolia, Cüneyt Akal, Cahi̇t Helvaci Jan 1999

Mafic Microgranular Enclaves In The Kozak Granodiorite, Western Anatolia, Cüneyt Akal, Cahi̇t Helvaci

Turkish Journal of Earth Sciences

Enclaves which are relicts of initial basic magma give important information on the origin and evolution of granitic magmas. The mafic microgranular enclaves from the l-type Kozak pluton are less than 1 m that are located at the margin of pluton and mostly less than 15 cm and are generally in sharp contact with the surrounding granodiorite. In some cases, several enclaves may occur close to each other, but they are not closely clustered to form swarms. Most of the enclaves are ellipsoidal in shape. The largest enclaves are less ellipsoidal with curved boundaries. The mafic microgranular enclaves contain same …


Rock-Forming Nannofossils In Uppermost Jurassic-Lowercretaceous Rock Units Of Northwest Anatolia: Nannoconusand Its Resived Taxonomy, Sevi̇nç Özkan Altiner Jan 1999

Rock-Forming Nannofossils In Uppermost Jurassic-Lowercretaceous Rock Units Of Northwest Anatolia: Nannoconusand Its Resived Taxonomy, Sevi̇nç Özkan Altiner

Turkish Journal of Earth Sciences

Nannoconids have been recorded in a rock-forming quantity in the uppermost Jurassic-Lower Cretaceous rock units in Northwest Anatolia, Turkey. Samples were collected from seventeen stratigraphic sections spanning the calciturbidities of the Yosunlukbayiri Formation and pelagic micrites of the Sogukçam Limestone. Because of rareness and difficulties for extracting of calcareous nannofossil species particularly zone markers in these type lithologies, nannoconids have particular attention in terms of biostratigraphy. Twenty nine species of nannoconids were recorded in the studied samples. Their taxonomy were revised and their stratigraphic ranges were given. The classification of genus Nannoconusis based on the gross morphology of the test, …


Deformation Of Stibnites And Pyrites In The Madsan Antimony Deposit (Niğde, Turkey): Implications For Pressure-Temperatureconditions Of Local Deformation, İlkay Kuşcu, Ayhan Erler Jan 1999

Deformation Of Stibnites And Pyrites In The Madsan Antimony Deposit (Niğde, Turkey): Implications For Pressure-Temperatureconditions Of Local Deformation, İlkay Kuşcu, Ayhan Erler

Turkish Journal of Earth Sciences

The Madsan antimony deposit at the southeastern part of the Niğde province (south-central Turkey) includes a series of epithermal veins hosted by marbles and gneisses. The veins have a simple mineralogy of quartz, calcite, stibnite and pyrite as major constituents, and cinnabar occurs in trace amounts. The deposit experienced a progressive deformation evidenced by a set of textures developed especially in stibnite and pyrite. These are pressure lamellae and annealing as the main textures, and curvature, off-set of pressure lamellae and fracture filling as the textures of minor importance. These were developed in three successive deformation phases. Pressure lamellae represent …


Geology Of The Dereiçi (Şavsat, Artvin) Cu-Pb-Zn Deposits, Mesut Soylu, Ayhan Erler Jan 1999

Geology Of The Dereiçi (Şavsat, Artvin) Cu-Pb-Zn Deposits, Mesut Soylu, Ayhan Erler

Turkish Journal of Earth Sciences

The geological relationships between the rock units in the Dereiçi/Şavsat (Artvin) region and vein-type Cu-Pb-Zn deposits were presented in this paper. The study area comprises the Upper Cretaceous intermediate volcanic rocks and sedimentary rocks, with Post-Eocene dykes of andesitic and diabasic composition. The mineral deposits are classified as (1) Sphalerite-Galena-Chalcopyrite-Pyrite veins (Talatin Madeni, Binektasi and Fikrinin Madeni), (2) milky quartz-Chalcopyrite-Sphalerite-Galena-Pyrite veins and (3) Chalcopyrite-Pyrite veins. The general paragenetic sequence of the mineralizations is observed as quartz I-pyrite-chalcopyrite-sphalerite-galena-quartz II-chalcocite-covellite. The wall rocks are subjected to silicification, sericitic alteration, chloritization and carbonatization.


Along-Strike Discontinuity Of Active Normal Faults And Its Influence On Quaternary Travertine Deposition; Examples From Western Turkey, Zi̇yadi̇n Çakir Jan 1999

Along-Strike Discontinuity Of Active Normal Faults And Its Influence On Quaternary Travertine Deposition; Examples From Western Turkey, Zi̇yadi̇n Çakir

Turkish Journal of Earth Sciences

Detail mapping of active fault zones bounding four travertine masses in the Gediz and Menderes grabens of western Turkey revealed that they are divided into geometric fault segments up to 13 km long. Fissures, supplying the carbonate-rich waters that give rise to the travertines are preferentially developed at the ends of the fault segments or in extensional step-over zones where the offset between the fault strands is about 1 km or more. The deposition of travertines in such structural settings is probably a consequence of the network of fissures supplying the carbonate-rich waters being highly interconnected where extensional strains were …


A New Formalism For Nonextensive Physical Systems: Tsallis Thermostatistics, Uğur Tirnakli, Fevzi Büyükkiliç, Doğan Demi̇rhan Jan 1999

A New Formalism For Nonextensive Physical Systems: Tsallis Thermostatistics, Uğur Tirnakli, Fevzi Büyükkiliç, Doğan Demi̇rhan

Turkish Journal of Physics

Although Boltzmann-Gibbs (BG) statistics provides a suitable tool which enables us to handle a large number of physical systems satisfactorily, it has some basic restrictions : (i) the range of the microscopic interactions must be small compared to the linear size of the macroscopic systems (short-range interactions) , (ii) the time range of the microscopic memory must be small compared to the observation time (Marcovian processes) and (iii) the system must evolve in an Euclidean-like space-time. In the case of a breakdown in one and/or the others of these restrictions, BG statistics fails. More precisely, the situation could be classified …


Assessment Of The Degree Of Mix Of Powder Mixtures, Orhan Vai̇zoğlu Jan 1999

Assessment Of The Degree Of Mix Of Powder Mixtures, Orhan Vai̇zoğlu

Turkish Journal of Physics

The older methods for the determination of the degree of a random mix was solely based on the calculation of a simple standard deviation. Physical characteristics like, density, average particle weight and size of each component was not considered. Therefore, the evaluation, when the state of a random mix is reached, was somewhat superficial. Poole, Taylor, and Wall [1] have derived equations, where the physical characteristics of the components were taken into consideration. By this means, it is possible to calculate, in advance, the theoretical coefficient of variation and the corresponding confidence limits. One can then experimentally follow under which …


Diverging Strains Near Threshold: Breakdown Of The Elastic Description Of A Charge Density Wave Model, Muhittin Mungan, Susan N. Coppersmith, Valeri M. Vinokur Jan 1999

Diverging Strains Near Threshold: Breakdown Of The Elastic Description Of A Charge Density Wave Model, Muhittin Mungan, Susan N. Coppersmith, Valeri M. Vinokur

Turkish Journal of Physics

We analyze the strains near threshold in 1-d charge density wave models at zero temperature and strong pinning. We show that in these models local strains diverge near the depinning threshold and characterize the scaling behavior of the phenomenon. This helps quantify when the underlying elastic description breaks down and plastic effects have to be included.


Electron Liquid Beyond The Random Phase Approximation, Mehmet Tomak, Ceyhun Bulutay Jan 1999

Electron Liquid Beyond The Random Phase Approximation, Mehmet Tomak, Ceyhun Bulutay

Turkish Journal of Physics

A deeper understanding of low-dimensional and small-scale electronic systems requires an accurate characterization of the many-electron effects. Based on the electron liquid (EL) model, these many-body effects in the three-dimensional (3D) and two-dimensional (2D) electronic systems are dealt going beyond the random phase approximation within the zero-temperature framework. The dielectric formulation of the many-body problem is recapitulated and the longitudinal dielectric function of the EL is obtained using the self-consistent local-field correction scheme, known as STLS, under a general spin-valley degeneracy. Extensive explicit expressions are provided for the use of other researchers. The performance of this formalism is compared in …


Spectral Broadening Functions, Slavek Rucinski Jan 1999

Spectral Broadening Functions, Slavek Rucinski

Turkish Journal of Physics

Many astrophysical phenomena involving velocity fields produce broadening of spectral lines. Frequently, the cross-correlation function (CCF) is used to extract information about this broadening from segments of high resolution spectra. CCF has become the standard tool for handing extraction of radial-velocity and broadening information from high resolution spectra as it permits integration of information which is common to many spectral lines into one function which is easy to calculate, visualize and interpret. However, it can be argued that this is not the best tool for applications such as determinations of metallicities ([Fe/H]), for finding locations of star spots on active …


Short-Period Rs Cvn And W Uma Binaries: How Are They Related?, Frans Van't Veer Jan 1999

Short-Period Rs Cvn And W Uma Binaries: How Are They Related?, Frans Van't Veer

Turkish Journal of Physics

Two groups of late-type very close main sequence binaries, the so-called short-period RS Canum Venaticorum (RS CVn) and W Ursae Majoris (W UMa) systems, are important for the understanding of the structure and evolutionary consequencies of angular momentum loss (AML) resulting from magnetic stellar winds of fast rotating solar type stars. The components of RS CVn stars are close to their Roche lobes, but still detached, whereas W UMa binaries are contact systems; both are rotating fast. One of the crucial problems is trying to answer the question if there is a dynamical relation between the two types of binaries …


Photon Counting In Astrophotometry. Fundamentals And Some Advices For Beginners, Romualdas Kalytis Jan 1999

Photon Counting In Astrophotometry. Fundamentals And Some Advices For Beginners, Romualdas Kalytis

Turkish Journal of Physics

The beginners in astrophotometry are reminded of fundamentals of photon counting. Several advices for new users of electrophotometric technics are given.


Photometric Imaging Of Starspots, Techniques And Reliability, Zeki̇ Eker Jan 1999

Photometric Imaging Of Starspots, Techniques And Reliability, Zeki̇ Eker

Turkish Journal of Physics

Historical development of the starspot hypothesis and the unsolved problems associated with it are presented. The "non{uniqueness" attributed to the spot solutions is a major problem which could still discredit current efforts of starspot modeling by photometric or spectroscopic data. The basics of the starspot photometry(direct and inverse photometric problem, and the error analysis of the inverse problem) are presented. Since an analytical formulation exists to compute synthetic light curves from the physical parameters of spots, and recomputing original parameters analytically from the synthetic curves are also possible, the starspot hypothesis is a consistent physical problem. According to the error …


Facular Structures On Cool Stars, Serdar Evren Jan 1999

Facular Structures On Cool Stars, Serdar Evren

Turkish Journal of Physics

Activity has many manifestations, from dark spots to bright regions, to the presence of the heated chromosphere, to the superheated corona. Sunspots are extended, strongly magnetic regions on the Sun. Photospheric faculae are generally visible only at the limb. Polar faculae are smaller than the main-zone faculae. The contributions of the active region faculae and the facular network are at least as important as the solar spots in augmenting the solar emission.


Dynamical Evolution Of The Rs Cvn-Type Binaries, Osman Demi̇rcan Jan 1999

Dynamical Evolution Of The Rs Cvn-Type Binaries, Osman Demi̇rcan

Turkish Journal of Physics

The orbital angular momentum (orbital AM) of a sample of forty RS CVn-type binaries with the orbital periods P \leq 10 days were estimated and the orbital AM distribution with respect to P was critically interpreted as the orbital AM evolution of these systems caused by the magnetic breaking process with the existence of spin-orbit coupling. The empirical relations (between the orbital AM loss, mass loss and period variation) derived from the diagram of the orbital AM distribution were used in deriving a semi-empirical formula for the dynamical evolution of the RS CVn-type binaries. The magnetic breaking induced dynamical evolution …


Co-Ordinated Multi-Wavelength Observations Of The Rs Cvn System Cf Tuc, Edwin Budding, K. L. Jones, O. B. Slee, L. Watson Jan 1999

Co-Ordinated Multi-Wavelength Observations Of The Rs Cvn System Cf Tuc, Edwin Budding, K. L. Jones, O. B. Slee, L. Watson

Turkish Journal of Physics

A `multi-site, multi-wavelength' campaign on the eclipsing RS CVn binary CF Tuc was carried out in 1996 over both optical (photometry and spectroscopy) and radio (microwave) ranges. The microwave data was taken with the Australia Telescope Compact Array (ATCA). It covered slightly more than one complete orbital cycle at 4.8 and 8.64 GHz in one continuous run. There was also coverage of about 25% of the light curve at 1.38 and 2.38 GHz. High dispersion spectroscopy was obtained using the McLellan 1m telescope and échelle spectrograph at Mt John University Observatory (New Zealand). Supporting photometry came from various smaller-scale facilities …


Ionizing Radiations And Annealing Influence On Mosfet Charge States, Zainabidinov Ciragiddin, Atamuratov Atabek, Ysupov Akhmed, Adinaev Kuvondik Jan 1999

Ionizing Radiations And Annealing Influence On Mosfet Charge States, Zainabidinov Ciragiddin, Atamuratov Atabek, Ysupov Akhmed, Adinaev Kuvondik

Turkish Journal of Physics

The threshold voltage shift \Delta V_T and its components due to trapped-oxide charges \Delta V_{Not} and Si-SiO_2 interface traps \Delta V_N in MOSFET exposed to Bremsstrahlung, Co_{60} irradiation and annealing were studied. Several effects caused by differences in the photon energies from two types of sources are discussed as well as a mechanism of changing the trapped-oxide and Si-SiO_2 interface traps by annealing. The mechanism is based on previously available models.


Determination Of Partial Coordinate Number Of Atoms In Amorphous Yb-As-S(Se, Te) Systems, Rasi̇m Ali̇-Zade, Eldar Efendi̇yev, Elman Haji̇yev Jan 1999

Determination Of Partial Coordinate Number Of Atoms In Amorphous Yb-As-S(Se, Te) Systems, Rasi̇m Ali̇-Zade, Eldar Efendi̇yev, Elman Haji̇yev

Turkish Journal of Physics

Partial coordinate number for amorphous compounds, consisting three type of atoms has been determined by way of calculation of the radial distribution curve maximum. The equation solution method has been used as algorithm in programme, which writed in FORTRAN language for working in IBM compatible computers. The programme is compact and integable. The programme has been used for determination partial coordinate number of ytterbium atom in amorphous compounds- YbAs_2S_4, Yb_3As_4S_9, YbAs_4Te_7, Yb_3As_4Se_9 YbAs_4Se_7. Real value of partial coordinate number of ytterbium in this compunds is 2 or 3.


Calibration Of Millimetric Marmara Radio Telescope And Radio Detection Of Ozone Line Over Gebze/Kocaeli In Turkey, Mehmet Emi̇n Özel, I. M. Yusifov, A. O. Allakhverdiev, A. A. Vertiy, G. Bayer, Osman Demi̇rcan, H. Kirbiyik, T. Adigüzel Jan 1999

Calibration Of Millimetric Marmara Radio Telescope And Radio Detection Of Ozone Line Over Gebze/Kocaeli In Turkey, Mehmet Emi̇n Özel, I. M. Yusifov, A. O. Allakhverdiev, A. A. Vertiy, G. Bayer, Osman Demi̇rcan, H. Kirbiyik, T. Adigüzel

Turkish Journal of Physics

A brief description of the calibration procedures for the millimetric Marmara Radio Telescope, MRT-2 is presented. Observations carried out during the spectroscopic calibration work is indicative of daily variations of Ozone line of sight density over the telescope location. This being also the first radio observations carried out in Turkey, a short account of observations and results are given.


Magnetodielectrical Polymer Compositional Materials, Sh. V. Mamedov, Y. Lenger, Sevi̇l Bolcal, Vilayet A. Alekperov, M. A. Ramazanov, R. Z. Sadikhov Jan 1999

Magnetodielectrical Polymer Compositional Materials, Sh. V. Mamedov, Y. Lenger, Sevi̇l Bolcal, Vilayet A. Alekperov, M. A. Ramazanov, R. Z. Sadikhov

Turkish Journal of Physics

Magnetodielectrical polymer compositional materials containing carbonyl iron (CI) were obtained. The changes of permittivity and permeability, loss angle tangent, resistivity, mechanical and electrical properties, depending on the content of carbonyl iron have been investigated. It is shown that the magnetodielectrical materials with 20-40% mass content of carbonyl iron have possible practical use.


Electrons And Phonons In Gan Semiconductor Quantum Well Devices, M. Babiker, N. A. Zakhleniuk, C. R. Bennett, V. N. Stavrou, B. K. Ridley Jan 1999

Electrons And Phonons In Gan Semiconductor Quantum Well Devices, M. Babiker, N. A. Zakhleniuk, C. R. Bennett, V. N. Stavrou, B. K. Ridley

Turkish Journal of Physics

Electrons and polar optical phonons and their interactions are considered in the context of semiconductor quantum well devices, with particular reference to real quantum well laser structures. Distinction is made between wide-barrier and narrow-barrier structures and we explore the implications of these regimes for the description of the electron capture process. Special emphasis is made on the significant effects arising from the large effective mass ratio in AlN/GaN structures.


Heat Pulse Studies Of The Emission And Absorption Of Acoustic Phonons In Gaas Quantum Wells And Wires, A. J. Kent Jan 1999

Heat Pulse Studies Of The Emission And Absorption Of Acoustic Phonons In Gaas Quantum Wells And Wires, A. J. Kent

Turkish Journal of Physics

This paper reviews some recent experiments in which heat pulse techniques have been used to study the interaction of acoustic phonons with electrons in semiconductor quantum wells and wires. Heat pulse experiments provide temporal and spatial resolution of the phonons that are emitted or absorbed by the electrons and so give more detailed information about the electron-phonon interaction than can be obtained by other methods (e.g. transport measurements). Phonon experiments demonstrate clearly the effect of the electron confinement on the carrier-phonon interaction and the overall energy loss rate due to acoustic phonon emission. A qualitative explanation of the results is …


Electrons In Large-Bandgap Bulk Semiconductors And Quantum Wells, N. A. Zakhleniuk, M. Babiker, C. R. Bennett, B. K. Ridley Jan 1999

Electrons In Large-Bandgap Bulk Semiconductors And Quantum Wells, N. A. Zakhleniuk, M. Babiker, C. R. Bennett, B. K. Ridley

Turkish Journal of Physics

The analytical theory of hot electrons interacting with lattice vibrations, impurities, and interface roughness in quantum wells is developed. We have obtained new distribution functions which describe all the kinetic properties of the non-equilibrium electron gas. As a specific example we present the electric field dependence of the electron mobility in GaN-based quantum wells and in bulk GaN. The relative importance of the different scattering mechanisms is analysed in detail.


Coherent Control Experiments As A Probe Of The Carrier Scattering Processes, P. Le Jeune, X. Marie, T. Amand, M. Paillard, J. Barrau Jan 1999

Coherent Control Experiments As A Probe Of The Carrier Scattering Processes, P. Le Jeune, X. Marie, T. Amand, M. Paillard, J. Barrau

Turkish Journal of Physics

We report on coherent control experiments of excitons in GaAs/AlGaAs Quantum wells.This technique, which relies on the linear response of the crystal,is used to investigate the spin-dependent exciton-exciton scattering.


Energy Relaxation Rate Of Hot Electrons In N-Type Gan Epilayers Using Heat Pulse Techniques, P. Hawker, A. J. Kent, T. S. Cheng, C. T. Foxon Jan 1999

Energy Relaxation Rate Of Hot Electrons In N-Type Gan Epilayers Using Heat Pulse Techniques, P. Hawker, A. J. Kent, T. S. Cheng, C. T. Foxon

Turkish Journal of Physics

We have measured the energy relaxation rate of hot electrons in MBE grown bulk GaN epilayers on GaAs and sapphire substrates over the electron temperature range 1 - 130 K. The measurements were made using heat pulse techniques. For layers grown on GaAs substrates the results show that the carriers reside in the substrate, probably as in a GaAs/AlGaAs heterojunction. For layers grown on sapphire substrates we obtain a P \propto T^4_e dependence for the relaxation rate in the low temperature limit, consistent with piezoelectric coupling in the so-called `dirty' regime, changing to a linear dependence in the high temperature, …


Feasibility Of The Gainp/Ingaas/Gaas System For Modulation Doped Field-Effect Transistors, C. Besi̇kci̇, Y. Ci̇van Jan 1999

Feasibility Of The Gainp/Ingaas/Gaas System For Modulation Doped Field-Effect Transistors, C. Besi̇kci̇, Y. Ci̇van

Turkish Journal of Physics

Si-doped single Ga_{0.51}In_{0.49}P layers and GaInP/InGaAs/GaAs modulation doped field-effect transistor structures grown by gas source molecular beam epitaxy were characterized in detail through Hall-Effect and Deep Level Transient Spectroscopy techniques. Electrical characterization of the undoped and moderately Si-doped (N_D = 3 x 10^{17} cm^{-3}) GaInP layers yielded an electron trap with an activation energy of 0.75 eV and a temperature dependent capture cross section with a capture barrier of 0.593 eV showing DX center properties. The trap was not detected in highly Si doped (N_D = 4 x 10^{18} cm^{-3}) as grown layers suggesting that it is a defect complex …