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Graphene, that is a monolayer of carbon atoms arranged in a honeycomb lattice, has been isolated only recently from graphite. This material shows very attractive physical properties, like superior carrier mobility, current carrying capability and thermal conductivity. In consideration of that, graphene has been the object of large investigation as a promising candidate to be used in nanometer-scale devices for electronic applications. In this work, graphene nanoribbons (GNRs), that are narrow strips of graphene, for which a band-gap is induced by the quantum confinement of carriers in the transverse direction, have been studied. As experimental GNR-FETs are still far from being ideal, mainly due to the large width and edge roughness, an accurate description of the physical phenomena occurring in these devices is required to have valuable predictions about the performance of these novel structures. A code has been developed to this purpose and used to investigate the performance of 1 to 15-nm wide GNR-FETs. Due to the importance of an accurate description of the quantum effects in the operation of graphene devices, a full-quantum transport model has been adopted: the electron dynamics has been described by a tight-binding (TB) Hamiltonian model and transport has been solved within the formalism of the non-equilibrium Green's functions (NEGF). Both ballistic and dissipative transport are considered. The inclusion of the electron-phonon interaction has been taken into account in the self-consistent Born approximation. In consideration of their different energy band-gap, narrow GNRs are expected to be suitable for logic applications, while wider ones could be promising candidates as channel material for radio-frequency applications.

The low-field channel mobility of graphene nanoribbon (GNR) FETs is investigated through an atomistic full-quantum numerical model including elastic acoustic phonon (AP) scattering and edge roughness (ER), the latter being treated via a direct statistical approach. We find that, for narrow GNRs (W = 1 ÷ 2 nm), quantum localization effects due to ER become important, so that it is not possible to define an ER limited mobility. In this regime, the inclusion of AP scattering results in a current increase rather than decrease, due to phase breaking, which partially recovers the ohmic regime. The resulting total mobility extracted from a long channel GNR-FET biased in the ON-state is not far from the measured mobility of a GNR of comparable dimensions.

High electric fields and temperatures in high-voltage ICs (HV-ICs) can induce charge transport phenomena in the encapsulation material leading to reliability test failures. In this paper, the resistivity of epoxy-based resins with insulating microfiller weight fraction exceeding 70% has been experimentally and theoretically investigated for the first time. Electrical conductivity has been measured at high temperature (150 °C) using both dielectric spectroscopy analysis on bulk samples and charge-spreading characterizations on a dedicated test chip with integrated charge sensors. The use of a charge sensor close to the internal HV metallization leads to results more pertinent with the active area of HV-ICs. Remarkably, both experiments show an unexpected increase and a significant variability of the electrical conductivity as the microfiller fraction is increased. The strong correlation between bulk and lateral experiments clearly indicates that those features should be attributed to the bulk material. Numerical simulations of diffusion phenomenon in mold structures with random arrangements of spherical microfillers demonstrate that the conductivity increase with filler content can be ascribed to the role of the epoxy/filler interfaces.

Four molding-compound composites with different silica micro-filler size and concentration have been measured on top of dedicated IC test structures. The leakage current of charge sensors has been monitored under different high-voltage stress during charging/discharging transients occurring in the mold. Physical insight of space charge distribution at high electric field and temperature has been obtained by TCAD analysis. The role played by the encapsulation composition on the device-package interaction has been investigated via TCAD simulations of the HTRB test of a Single-RESURF LDMOS.