Scaling Behavior of InAlN/GaN HEMTs on Silicon for RF Applications

Due to the low cost and the scaling capability of Si substrate, InAlN/GaN high-electron-mobility transistors (HEMTs) on silicon substrate have attracted more and more attentions. In this paper, a high-performance 50-nm-gate-length InAlN/GaN HEMT on Si with a high on/off current (Ion/Ioff) ratio of 7.28 × 106, an average subthreshold swing (SS) of 72 mV/dec, a low drain-induced barrier lowing (DIBL) of 88 mV, an off-state three-terminal breakdown voltage (BVds) of 36 V, a current/power gain cutoff frequency (fT/fmax) of 140/215 GHz, and a Johnson’s figure-of-merit (JFOM) of 5.04 THz∙V is simultaneously demonstrated. The device extrinsic and intrinsic parameters are extracted using equivalent circuit model, which is verified by the good agreement between simulated and measured S-parameter values. Then the scaling behavior of InAlN/GaN HEMTs on Si is predicted using the extracted extrinsic and intrinsic parameters of devices with different gate lengths (Lg). It presents that a fT/fmax of 230/327 GHz can be achieved when Lg­ scales down to 20 nm with the technology developed in the study, and an improved fT/fmax of 320/535 GHz can be achieved on a 20-nm-gate-length InAlN/GaN HEMT with regrown ohmic contact technology and 30% decreased parasitic capacitance. This study confirms the feasibility of further improvement of InAlN/GaN HEMTs on Si for RF applications.

Scaling Behavior of Sub-100 nm InAlN/GaN HEMTs on Silicon for RF Applications

Due to the low cost and the scaling capability of Si substrate, InAlN/GaN high-electron-mobility transistors (HEMTs) on silicon substrate have attracted more and more attentions. In this paper, a high-performance 50-nm-gate-length InAlN/GaN HEMT on Si with a high on/off current (Ion/Ioff) ratio of 7.28 × 106, an average subthreshold swing (SS) of 72 mV/dec, a low drain-induced barrier lowing (DIBL) of 88 mV, an off-state three-terminal breakdown voltage (BVds) of 36 V, a current/power gain cutoff frequency (fT/fmax) of 140/215 GHz, and a Johnson’s figure-of-merit (JFOM) of 5.04 THz∙V is simultaneously demonstrated. The device extrinsic and intrinsic parameters are extracted using equivalent circuit model, which is verified by the good agreement between simulated and measured S-parameter values. Then the scaling behavior of InAlN/GaN HEMTs on Si is predicted using the extracted extrinsic and intrinsic parameters of devices with different gate lengths (Lg). It presents that a fT/fmax of 230/327 GHz can be achieved when Lg­ scales down to 20 nm with the technology developed in the study, and an improved fT/fmax of 320/535 GHz can be achieved on a 20-nm-gate-length InAlN/GaN HEMT with regrown ohmic contact technology and 30% decreased parasitic capacitance. This study confirms the feasibility of further improvement of InAlN/GaN HEMTs on Si for RF applications.

Performance enhancement of GaSb vertical nanowire p-Type MOSFETs on Si by rapid thermal annealing

GaSb is considered as an attractive p-type channel material for future III-V metal-oxide-semiconductor (MOS) technologies, but the processing conditions to utilize the full device potential such as low power logic applications and RF applications still need attention. In this work, applying rapid thermal annealing (RTA) to nanoscale GaSb vertical nanowire p-type MOSFETs, we have improved the average peak transconductance (g m,peak) by 50% among 28 devices and achieved 70 µS/µm at V DS = – 0.5 V in a device with 200-nm gate length. In addition, a low subthreshold swing down to 144 mV/dec as well as an off-current below 5 nA/µm which refers to the off-current specification in low-operation-power (LOP) condition has been obtained. Based on the statistical analysis, the results show a great enhancement in both on- and off-state performance with respect to previous work mainly due to the improved electrostatics and contacts after RTA, leading to a potential in low-power logic applications. We have also examined a short channel device with L g = 80 nm in RTA, which shows an increased gm,peak up to 149 µS/µm at V DS = – 0.5 V as well as a low on-resistance of 4.7 kΩ·µm. The potential of further enhancement in g m via RTA offer a good alternative to obtain high-performance devices for RF applications which have less stringent requirement for off-state performance. Our results indicate that post-fabrication annealing provides a great option to improve the performance of GaSb-based p-type devices with different structures for various applications.

Junctionless Gate-All-Around Nanowire FET with Asymmetric Spacer for Continued Scaling

In this paper we have performed scaling performance of asymmetric junctionless (JL) SOI nanowire FET at 10 nm gate length (LG). To study the device electrical performance various DC metrics like SS, DIBL, ION/IOFF ratio are performed. Even at 5 nm, the device has good electrical properties with subthreshold swing (SS) = 64 mV/dec, drain induced barrier lowering (DIBL) = 45 mV/V, and switching ratio (ION/IOFF) = 106 shows a higher level of electrostatic integrity. Moreover, to study scaling flexibility towards analog/RF applications various parameters like transconductance (I), transconductance generation factor (TGF), total gate capacitance (Cgg), and cutoff frequency (fT) are determined. Furthermore, the dynamic power (DP) and static power (SP) consumption of the device with scaling is also presented. The findings of the study show that asymmetric JL nanowire FET is one of the scaling possibilities.

Impact of Tip Design and Thermocouple Location on the Efficacy and Safety of Radiofrequency Application

Background & Objectives The FlexAbilityTM SE catheter has a laser-cut 8Fr 4-mm flexible tip irrigated through laser-cut kerfs with a thermocouple 0.3mm from the distal end. The TactiCathTM SE catheter has an 8Fr 3.5-mm tip and 6-irrigation port with a thermocouple 2.67mm proximal to the tip. We investigated the impact of these differences on the efficacy and safety of RF-applications. Methods RF applications at a range of powers (20W, 30W, and 40W), contact forces (5g, 15g, and 25g), and durations (10-60s) using perpendicular/parallel catheter orientation, were performed in excised porcine hearts. Lesion characteristics and incidence of steam pops were compared. Results 540 lesions were examined. The FlexAbilityTM SE catheter produced smaller lesion depths (4.0mm vs. 4.4mm, p=0.014 at 20W; 4.6mm vs. 5.6mm, p=0.015 at 30W), surface areas (22.7mm2 vs. 29.2mm2 at 20W, p=0.005; 23.2mm2 vs. 28.7mm2, p=0.009 at 30W) and volumes (126.1mm3 vs. 175.1mm3, p=0.018 at 20W; 183.2mm3 vs. 304.3mm3, p=0.002 at 30W) with perpendicular catheter placement. However, no differences were observed with parallel catheter placement. Steam-pops were significantly less frequently observed with the FlexAbilityTM SE catheter (4% vs. 22%, p<0.001) irrespective of catheter direction to the tissue. Multivariate analysis showed that use of the TactiCathTM SE catheter, power ≥40W, contact force ≥25g, RF duration >30s, parallel angle and impedance drop ≥20Ω were significantly associated with occurrence of steam-pops. Conclusions The FlexAbilityTM SE catheter reduced the risk of steam-pops, but produced smaller lesions with perpendicular catheter placement compared to the TactiCathTM SE catheter.