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We present a novel graphene-based-device concept for a high-frequency operation: a hot-electron graphene base transistor (GBT). Simulations show that GBTs have high current on/off ratios and high current gain. Simulations and small-signal models indicate that it potentially allows terahertz operation. Based on energy-band considerations, we propose a specific material solution that is compatible with SiGe process lines. © 2012 IEEE.

Si(sub 1-y)C(sub y) layers grown pseudomorphically on Si(001) with constant carbon and Si fluxes, but at various growth temperatures, were studied by in vacuu x-ray photoelectron spectroscopy. The total carbon concentration was constant in all the layers, but the amount of substitutionally incorporated carbon decreased with increasing temperature. The carbon concentration increased toward the sample surface with increasing growth temperatures. This was caused by the surface segregation of carbon atoms during growth.

Experimental determination of the effect of molecular-beam-epitaxy growth and antimony-mediated growth on the properties of germanium single quantum wells (QWs) on (001) silicon matrix shows that QWs grown using molecular-beam-epitaxy display segregation-induced alloying while antimony-mediated growth conditions confer the best interface sharpness to the QWs at 450 degrees Celsius. Annealing at high temperatures following growth induces Ge and Si interdiffusion that enhance alloying. Antimony-mediated growth conditions enable the surfactant to promote the bulk properties of germanium at high temperatures.

Micro Raman backscattering, X-ray double crystal diffractometry and transmission electron microscopy are used to investigate the epitaxial Si(1-x)Ge(x) layers, grown by molecular beam epitaxy. The epitaxial Si(1-x)Ge(x) layers, grown by chemical vapor deposition on Si substrates with thickness between 20 and 50 nanometers, are also investigated. The Raman shift of the Si-Si mode as a function of the germanium content is also derived by a simple phenomenological model. The Raman shift also yields the degree of relaxation, independently determined from the germanium content.

The electrical characteristics of layered [Al.sub.2][O.sub.3]/[Pr.sub.2][O.sub.3]/[Al.sub.2][O.sub.3] metal-insulator-metal (MIM) capacitors for RF device applications are described. This advanced dielectric layer system has shown a high capacitance density, a low leakage current density and an excellent dielectric loss behavior over the studied frequency range.

Engineered dielectrics combined with compatible metal electrodes are important materials science approaches to scale three-dimensional trench dynamic random access memory (DRAM) cells. Highly insulating dielectrics with high dielectric constants were engineered in this study on TiN metal electrodes by partly substituting Al in the wide band gap insulator Al2O3 by Pr cations. High quality PrAlO3 metal-insulator-metal capacitors were processed with a dielectric constant of 19, three times higher than in the case of Al2O3 reference cells. As a parasitic low dielectric constant interface layer between PrAlO3 and TiN limits the total performance gain, a systematic nondestructive synchrotron x-ray photoelectron spectroscopy study on the interface chemistry of PrxAl2-xO3 (x=0–2) dielectrics on TiN layers was applied to unveil its chemical origin. The interface layer results from the decreasing chemical reactivity of PrxAl2-xO3 dielectrics with increasing Pr content x to reduce native Ti oxide compounds present on unprotected TiN films. Accordingly, PrAlO3 based DRAM capacitors require strict control of the surface chemistry of the TiN electrode, a parameter furthermore of importance to engineer the band offsets of PrxAl2-xO3/TiN heterojunctions. [ABSTRACT FROM AUTHOR]

The structure of ultrathin epitaxial Pr2O3 films on Si(111) was studied by synchrotron radiation-grazing incidence x-ray diffraction. The oxide film grows as hexagonal Pr2O3 phase with its (0001) plane attached to the Si(111) substrate. The hexagonal (0001) Pr2O3 plane matches the in-plane symmetry of the hexagonal Si(111) surface unit cell by aligning the (10&1bar;0)Pr2O3 along the (11&2bar;) Si directions. The small lattice mismatch of 0.5% results in the growth of pseudomorphic oxide films of high crystalline quality with an average domain size of about 50 nm. The critical thickness tc for pseudomorphic growth amounts to 3.0± 0.5 nm. The relaxation of the oxide film from pseudomorphism to bulk behavior beyond tc causes the introduction of misfit dislocations, the formation of an in-plane small angle mosaicity structure, and the occurence of a phase transition towards a (111) oriented cubic Pr2O3 film structure. The observed phase transition highlights the influence of the epitaxial interface energy on the stability of Pr2O3 phases on Si(111). A mechanism is proposed which transforms the hexagonal (0001) into the cubic (111) Pr2O3 epilayer structure by rearranging the oxygen network but leaving the Pr sublattice almost unmodified. [ABSTRACT FROM AUTHOR]

Highly insulating dielectrics dielectric with high dielectric constants are engineered on TiN metal electrodes by partly substituting Al in the wide band gap insulator [Al.sub.2][O.sub.3] by Pr cations. PrAl[O.sub.3] based dynamic random access memory (DRAM) capacitors needs strict control of the surface chemistry of the TiN electrode, a parameter that is important for engineering the band offsets of [Pr.sub.x][Al.sub.2-x][O.sub.3]/TiN heterojunctions.

The structure of ultrathin epitaxial Pr2O3 films on Si(111) is studied by synchrotron radiation-grazing incidence x-ray diffraction. The oxide film grows as hexagonal Pr2O3 phase with its (0001) plane attached to the Si(111) substrate.

Presents a study which investigated surfactant-mediated growth of germanium (Ge) on silicon (001) with submonolayer coverages of antimony and tellurium using reflection high-energy electron diffraction and transmission electron microscopy. Discussion on the growth of smooth epitaxial germanium layers on silicon; Details of an experiment on antimony- and tellurium-mediated growth of Ge; Results and discussion.

The development of 94-GHz traveling wave tubes for military radar applications is discussed.