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This paper reviews the experimental and theoretical state of the art in ballistic hot electron transistors that utilize two-dimensional base contacts made from graphene, i.e. graphene base transistors (GBTs). Early performance predictions that indicated potential for THz operation still hold true today, even with improved models that take non-idealities into account. Experimental results clearly demonstrate the basic functionality, with on/off current switching over several orders of magnitude, but further developments are required to exploit the full potential of the GBT device family. In particular, interfaces between graphene and semiconductors or dielectrics are far from perfect and thus limit experimental device integrity, reliability and performance., QC 20160118

We demonstrate molecular beam growth of graphene on biotite mica substrates at temperatures below 1000 °C. As indicated by optical and atomic force microscopy, evaporation of carbon from a high purity solid-state source onto biotite surface results in the formation of single-, bi-, and multilayer graphene with size in the micrometer regime. It is shown that the graphene grown directly on mica surface is of very high crystalline quality with the defect density below the threshold detectable by Raman spectroscopy. The interaction between graphene and the mica substrate is studied by comparison of the Raman spectroscopy and atomic force microscopy data with the corresponding results obtained for graphene flakes mechanically exfoliated onto biotite substrates. Experimental insights are combined with density functional theory calculations to propose a model for the initial stage of the van der Waals growth of graphene on mica surfaces. This work provides hints on how the direct growth of high quality graphene on insulators can be realized in general without exceeding the thermal budget limitations of Si technologies., QC 20130215

Despite exceptional intrinsic properties of graphene, field effect transistors with graphene channels (GFETs) are limited by the absence of an electronic band gap. The resulting low ION-IOFF ratio and low output resistance makes GFETs unsuitable for logic applications [1] and limits radio frequency (RF) applications [2]. We will present a graphene-based electronic device in which the 0 eV band gap does not limit the device performance: a hot electron transistor (HET) with a graphene base (Graphene Base Transistor, GBT) [3,4]. The single-atomic thinness and high conductivity are decisive advantages of a graphene base [5]. Here, we report on the fabrication and full DC-characterization of GBTs with high ION-IOFF ratio of 105., QC 20140116

In this work, we propose an integration approach for double gate graphene field effect transistors. The approach includes a number of process steps that are key for microelectronics integration: bottom gates with ultra-thin (2nm) high-quality thermally grown SiO2 dielectrics, shallow trench isolation between devices and atomic layer deposited Al2O3 top gate dielectrics. The complete process flow is demonstrated with fully functional GFET transistors and can be extended to wafer scale processing and other graphene-based devices., QC 20130114

Realization of graphene devices is often hindered by the fact that the known layer growth methods do not meet the requirements of the device fabrication in silicon mainstream technology. For example, the relatively straightforward method of decomposition of hexagonal SiC is not CMOS-compatible due to the high-thermal budget it requires [Moon et al., IEEE Electron Device Lett. 31, 260 (2010)]. Techniques based on layer transfer are restricted because of the uncertainty of residual metal contaminants, particles, and structural defects. Of interest is thus a method that would allow one to grow a graphene film directly in the device area where graphene is needed. Production of large area graphene is not necessarily required in this case, but high quality of the film and metal-free growth on an insulating substrate at temperatures below 1000 degrees C are important requirements. We demonstrate direct growth of defect-free graphene on insulators at moderate temperatures by molecular beam epitaxy. The quality of the graphene was probed by high-resolution Raman spectroscopy, indicating a negligible density of defects. The spectra are compared with those from graphene flakes mechanically exfoliated from native graphite onto mica. These results are combined with insights from density functional theory calculations. A model of graphene growth on mica and similar substrates is proposed., QC 20130110

Strong effort is devoted to grow graphene directly on insulators to create a technological step towards cost effective mass production of high-frequency transistors on Si. We have shown recently, that direct graphene growth can be achieved on silicate substrates by solid carbon source deposition. Here, we present a study on the growth of graphene on insulator by means of Raman and photoelectron spectroscopy, corroborated by density functional theory calculations. We address temperature dependence and the correlation between graphene quality and the number of layers. We show that this approach may open a pathway to Si-compatible graphene growth for electronic applications., QC 20140911