Search

In this article, we have demonstrated 125-nm-gate InGaAs-on-insulator (InGaAs-OI) high-electron-mobility transistors (HEMTs) on Si substrates via wafer bonding. The highlights of this device were the i-In0.53Ga0.47As/i-InAs/i-In0.53Ga0.47As quantum-well channel for high RF performance by improving electron transport properties and the low processing temperature of 250 °C or less for monolithic 3-D integration. As a result, we obtained a current gain cutoff frequency (ƒT) of 227 GHz and a maximum oscillation frequency (ƒMAX) of 187 GHz. These results are the highest ever reported in monolithic 3-D RF transistors above LG = 100 nm. In addition, through the small-signal modeling, we have found that the impact of the back-gate (BG) on RF performances of top devices is a critical issue in M3D RF systems. [ABSTRACT FROM AUTHOR]

Simple and accurate circuit simulation model for gallium nitride (GaN) power field-effect transistors (FETs) is presented and validated in high-frequency low-voltage synchronous buck (SB) dc-dc power converters. For comparison, simulation results are also presented for the power converter based on silicon power metal-oxide semiconductor (MOS)FETs with similar voltage and current ratings. An improvement in power conversion efficiency of more than 4% is reported with GaN power FETs compared to the best commercially available silicon power MOSFETs in a 19 V/1.2 V, 7 W SB dc-dc power converter with excellent load regulation. A temperature- and frequency-dependent power inductor model is also reported and is shown to be necessary in order to accurately model the converter performance. [ABSTRACT FROM PUBLISHER]

This brief aims to show the effects of threading edge dislocations on the dc and RF performance of GaN high- electron mobility transistor (HEMT) devices. A state-of-the-art high-frequency and high-power HEMT was investigated with our full-band cellular Monte Carlo (CMC) simulator, which includes the full details of the band structure and the phonon spectra. A complete characterization of the device has been performed using experimental data to calibrate the few adjustable parameters of the simulator. Thermal simulations were also carried out with commercial software in order to operate the corrections needed to model thermal effects. The approach of Weimann based on the results of Read, Bonch-Bruevich and Glasko, and Pödör was then used to model with our CMC code the dislocation effects on the transport properties of HEMT devices. Our simulations indicate that GaN HEMT performance exhibits a fairly large dependence on the density of thread dislocation defects. Furthermore, we show that a threshold concentration exists, above which a complete degradation of the device operation occurs. [ABSTRACT FROM AUTHOR]

This paper presents a rigorous investigation of high-frequency effects in carbon nanotube (CNT) interconnects and their implications for the design and performance analysis of high-quality on-chip inductors. A frequency-dependent impedance extraction method is developed for both single-walled CNT (SWCNT) and multiwalled CNT (MWCNT) bundle interconnects. The method is subsequently verified by comparing the results with those derived directly from the Maxwell's equations. Our analysis reveals for the first time that skin effect in CNT (particularly MWCNT) bundles is significantly reduced compared to that in conventional metal conductors, which makes them very attractive and promising material for high-frequency applications, including high-quality (Q) factor on-chip inductor design in high-performance RF/mixed-signal circuits. It is shown that such unique high-frequency properties of CNTs essentially arise due to their large momentum relaxation time (leading to their large kinetic inductance), which causes the skin depths to saturate with frequency and thereby limits resistance increase at high frequencies in a bundle structure. It is subsequently shown that CNT-based planar spiral inductors can achieve more than three times higher Q factor than their Cu-based counterparts without using any magnetic materials or Q factor enhancement techniques. [ABSTRACT FROM AUTHOR]

This paper reviews the current state of research in carbon-based nanomaterials,.particularly the one-dimensional (1-D) forms, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs), whose promising electrical, thermal, and mechanical properties make them attractive candidates for next-generation integrated circuit (IC) applications. After summarizing the basic physics of these materials, the state of the art of their interconnect-related fabrication and modeling efforts is reviewed. Both electrical and thermal modeling and performance analysis for various CNT- and GNR-based interconnects are presented and compared with conventional interconnect materials to provide guidelines for their prospective applications. It is shown that single-walled, double-walled, and multiwalled CNTs can provide better performance than that of Cu. However, in order to make GNR interconnects comparable with Cu or CNT interconnects, both intercalation doping and high edge-specularity must be achieved. Thermal analysis of CNTs shows significant advantages in tall vias, indicating their promising application as through-silicon vias in 3-D ICs. In addition to on-chip interconnects, various applications exploiting the low-dimensional properties of these nanomaterials are discussed. These include chip-to-packaging interconnects as well as passive devices for future generations of IC technology. Specifically, the small form factor of CNTs and reduced skin effect in CNT interconnects have significant implications for the design of on-chip capacitors and inductors, respectively. [ABSTRACT FROM AUTHOR]

The Klaassen-Prins equation is the standard equation for calculating the drain thermal noise of long-channel MOSFETs. We show that the Klaassen-Prins equation is not always valid, even for MOSFETs. We present generalizations to the Klaassen-Prins equation that include velocity saturation effects of short-channel MOSFETs and that comprise also induced gate noise. [ABSTRACT FROM AUTHOR]