Transconductance Gm Research Articles

Impact of self-heating on RF/analog and linearity parameters of DMG FinFETs in underlap and overlap configurations

In this paper, the influence of self-heating effect (SHE) on the performance of Silicon on Insulator (SOI) dual material gate (DMG) FinFETs in underlap and overlap configurations for RF/analog applications is reported using three-dimensional TCAD simulators. The increase in electron velocity at channel surface is due to reduce effective electrical field at drain end, resulting in smaller DIBL and hot carrier effects. The device insights are reported by electron velocity, lattice temperature, thermal resistance, and output conductance versus frequency profiles. The findings on analog/RF figures of merit such as transconductance (gm), output conductance (gd), intrinsic gain (Ai), gate capacitance (Cgg), intrinsic delay (τ), cut-off frequency (fT), transconductance generation factor (TGF), gain frequency product (GFP), transconductance frequency product (TFP), and gain transconductance frequency product (GTFP) are reported with and without SHE. The results show that analog performance of Conventional and Underlap structures are improved but the influence of SHE is more deteriorating on Overlap structure. Furthermore, the linearity performance parameters VIP2, VIP3, IIP3, and 1 dB compression point are degraded with self-heating is due to increase in gm2 and gm3 values. It is seen that the gate overlap structure exhibits higher ON state performance which even after deterioration with Self-heating is still better than its counterparts as it has better gate controllability stemming from its lower effective channel length.

Nonalloyed ohmic contact development with n+ InGaN regrowth method and analysis of its effect on AlGaN/GaN HEMT devices

In this study, the DC performance of AlGaN/GaN based HEMT devices of different geometries (designed to operate in the S, X and Ka-band frequency ranges) with regrown degenerately doped n + In0.12GaN nonalloyed ohmic contacts on different epitaxial structures were investigated. Once the optimal recess etch depth and regrowth thickness for drain and source contacts were determined, the effects of alloyed and nonalloyed ohmic contacts on the maximum drain current (IDS,max), ON‐resistance (Ron), maximum DC transconductance (gm), pinch-off voltage (Vth), drain leakage current (ID,leak), and gate leakage current (IG,leak) were investigated for S, X and Ka-band HEMT devices. The results showed that the use of nonalloyed ohmic contacts resulted in decreasing Rc with a better surface morphology. Additionally, the nonalloyed ohmic contact structure with low contact resistance caused an increase in the IDS,max and gm values by reducing the Ron resistance, and also reducing the ID,leak and IG,leak leakage currents by preventing the surface distortions and trap formations due to the absence of high temperature. Although there was no dramatic change in Vth for S, X and Ka-band HEMT devices, Vth shifts towards positive in S and X-band devices, and towards negative in Ka-band devices.

Impact of interface trap charges on analog/RF and linearity performances of PGP negative capacitance FET

Here, we examine the impact of various trap charges on the baseline and NC PGPFET (negative capacitance partial ground plane FET) by applying localized charges (donor/acceptor) at the semiconductor/insulator interface. Examining different parameters has revealed that donor traps enhance device characteristics while acceptor traps reduce device performance. Therefore NC effect is generated by introducing a ferroelectric material in the gate stack that enhances the device performance by the voltage amplification process. Doped HfO2 is taken as the ferroelectric material because of its high dielectric capacitance and reliable polarization rate. Along with DC, RF/Analog factors such as trans-conductance (gm), output conductance (gds), trans-conductance generation factor (TGF), cut-off frequency (ft), trans-conductance frequency product (TFP) have been examined for the potential use of NCFET for RF applications. Additionally, linearity parameters like gm2, gm3, VIP2, VIP3 and intermodulation distortion (IMD3) is also compared for both traps. Due to its improved performance, NC PGPFET is appropriate for low-voltage analog/RF applications.

A comparative analysis of GaN and InGaN/GaN coupling channel HEMTs on silicon carbide substrate for high linear RF applications

In this work, we report comparative analysis of stable transconductance and high gain linearity for AlGaN and InAlN barrier-based HEMTs using an InGaN/GaN coupling channel with AlGaN back-barrier on Silicon carbide (SiC) substrate. The proposed InGaN/GaN coupling channel HEMTs showed flat transconductance and suppressed gm derivatives. LG 55 nm AlGaN (InAlN)/GaN conventional HEMTs showed 2.9 (3.8) A/mm of IDS, 0.59 (0.62) S/mm of transconductance (gm), 51.86 (27.42) V of VBR, 212 (233) GHz of fT, 242 (255) GHz of fMAX. Whereas, Lg 55 nm InGaN/GaN coupling channel-based AlGaN (InAlN) HEMT showed 3.3 (5.1) A/mm of IDS, 0.67 (0.71) S/mm of transconductance (gm), 53.12 (41.25) V of VBR, 251 (273) GHz of fT, 262 (283) GHz of fMAX. Moreover, high gate voltage swing (GVS) and larger OIP3 of proposed coupling channel HEMTs are suitable candidates for next-generation high linear RF applications.

Investigation on RF/Analog Performance in SiGe Pocket n-Tunnel FET

In this paper, a SiGe pocket n-TFET is designed and its electrical performance is extracted using a TCAD simulator. Initially, a comparative study of input characteristics among conventional TFET (Device 1), intrinsic SiGe pocket TFET (Device 2), and doped SiGe pocket TFET (Device 3) is presented. It is seen that Device 2 shows an improved switching ratio (ION/IOFF) compared to other Devices. Furthermore, the RF/analog performance such as transconductance (gm), output conductance (gd), intrinsic gain (gm/gd), gate capacitance (Cgg), cut-off frequency (fc), transconductance frequency product (TFP), gain frequency product (GFP), and gain transconductance frequency product (GTFP) is reported for the variation in x of SiGe pocket from 0 to 1. The eBTBT rate and electron density are plotted for the variation in x of SiGe pocket Vertical TFET. The results reveal that the increase in x leads to an improvement in RF/analog performance and the tunneling rate in SiGe pocket Vertical TFET.

Experimental and numerical studies on the power RF N-LDMOS transistor under cold and hot thermal shock tests based aging mechanism

This paper describes a new methodology to initiate a thermal accelerated aging test, and identify the key parameters affecting the reliability of a power RF N-LDMOS transistor. The method is based on two aging techniques namely cold and hot thermal shock tests (TST, air-air test), carried out at different junction temperatures varying from −25 °C to +75 °C as well as a deep theoretical analysis. We particularly focus on the thermal chock degradation of three important bond parameters: time, temperature and channel current. The experimental results show that the degradation phenomenon at cold TST is more important than at hot TST. Moreover, we observe an increase in the amplitude of the leakage gate current IGS as well as a shift in the following electric parameters: threshold voltage VTH, transconductance GM, on-state resistance RDSON, feedback capacity CRSS, and S parameters. 3D Silvaco-ATLAS based physical simulations are also carried out, and reveal the effect of the TST on the degradation of the structure zone, which in turn has led to the shift in the values of the electrical parameters. A deep theoretical analysis confirms the observed phenomenon, and shows that the degradation process leads to an increased carrier injection into the developed silicon dioxide layer (SiO2) and/or into the interface state Si/SiO2. Therefore, much more interface states are created due to a located maximum impact ionization rate at the gate.

N‐Type Glycolated Imide‐Fused Polycyclic Aromatic Hydrocarbons with High Capacity for Liquid/Solid‐Electrolyte‐based Electrochemical Devices

AbstractCurrently, n‐type small‐molecule mixed ionic‐electronic conductors remain less explored and their molecular design rules are not mature enough. Herein, two n‐type glycolated imide‐fused polycyclic aromatic hydrocarbons (IPAHs), d‐gdiPDI and t‐gdiPDI, are developed to probe the effects of molecular conformation on the electronic, electrochemical, morphological, and coupled ionic‐electronic transport properties. It is found that the highly twisted scaffold in d‐gdiPDI, compared to the nearly planar one of t‐gdiPDI, has a strong positive effect on the charge storage properties and thus the performance of organic electrochemical transistors (OECTs). d‐gdiPDI exhibits a volumetric capacitance of 657 F cm−3, obviously outperforming that of t‐gdiPDI (261 F cm−3), which is the highest value reported to date for small‐molecule OECT materials. Moreover, a high charge‐storage capacity of up to 479 F g−1 is observed for d‐gdiPDI. Arising from such high ionic‐electronic coupling characteristic, d‐gdiPDI‐based OECTs present a ≈2 × times higher geometry‐normalized transconductance (gm,norm) of 105.3 mS cm−1 relative to that of t‐gdiPDI counterparts. Significantly, further application of d‐gdiPDI in solid‐electrolyte OECTs delivers a gm,norm of 142.4 mS cm−1. These findings indicate that IPAHs are very promising candidates for n‐type small‐molecule OECTs and highlight the superiority of twisting conformation manipulation in materials design toward high‐performance electrochemical devices.

Functional Metal–Organic Frameworks for Maximizing Transconductance of Organic Photoelectrochemical Transistor at Zero Gate Bias and Biological Interfacing Application

AbstractOrganic electrochemical transistors showing maximum transconductance (gm) at zero gate bias (VG) is desired but has long been a challenge. To date, few solutions to this issue are available. Light‐matter interplay is shown as rich sources for optogenetics, photodynamic therapy, and advanced electronics, but its potential in gm modulation are largely untapped. Herein, the challenge is addressed by unique light‐matter interplay in the newly emerged technique of organic photoelectrochemical transistor (OPECT), which is exemplified by dual‐ligand photosensitive metal–organic frameworks (DL‐PS‐MOFs)/TiO2 nanorods (NRs) gated poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) OPECT under 425 nm light irradiation. Interestingly, the light stimulation on the DL‐PS‐MOFs can de‐dope PEDOT:PSS with altered transistor physics, achieving device showing maximum gm at zero VG and the simultaneous superior output of channel current. In connection to a cascade catalytic hairpin assembly‐rolling circle amplification strategy, such a device is then biologically interfaced with a miRNA‐triggered growth of DNA spheres for the sensitive detection of miRNA‐21 down to 0.12 fm. This work features a proof‐of‐concept study using light‐matter interplay to enable organic transistors showing maximum gm at zero VG and its sensitive biological interfacing application.

A 12.4–32 GHz CMOS Down-Conversion Mixer for 28 GHz 5G New Radio (NR)

We report a low voltage (VDD) and power (PDC) 12.4–32 GHz CMOS down-conversion mixer with high conversion gain (CG) for 28 GHz 5G communications. A quarter-wavelength (λ/4) transmission line (TL) and a coupling capacitor (Cc), named the λ/4-TL-C-based coupler, is proposed. This is the way to attain low-VDD, independent RF transconductance (gm)-stage bias, harmonic suppression, and near perfect coupling from the RF gm stage to the LO switch transistors. The body-self-forward-bias (BSFB) technique, i.e., connection of the gm-stage transistors’ body to drain via a large body resistance, is used for threshold voltage (Vth) and VDD reduction and substrate leakage suppression. CG and noise figure (NF) enhancement at the same or even a lower PDC is achieved because lower VDD and higher gm (due to larger bias current) are used. To facilitate the RF measurement, a compact Wilkinson-power-divider-based balun with small-phase deviation and amplitude imbalance is included at RF and LO inputs. The mixer consumes 6.5 mW and achieves a CG of 14.4 ± 1.5 dB for 12.4–32 GHz (i.e., 3 dB bandwidth (f3dB) of 19.6 GHz), a lowest noise figure (NFmin) of 7 dB, and figure-of-merit (FOM) of 0.023, which is one of the best results ever reported for millimeter-wave (mm-wave) down-conversion mixers with an f3dB larger than 10 GHz and PDC lower than 10 mW.

Performance analysis of GaN‐FINFET for RFIC application with respect to different FinWidth's

AbstractGaN has become a prevailing semiconductor in case of power and RF applications. The higher ranking material parameters of GaN, like wider band‐gap, the higher breakdown electric field as well as higher electron velocity when compared to materials like Si, SiC, GaAs etc; allow GaN FINFET to reveal potential advantages such as high voltage and high frequency applications. In this work, a comprehensive study on RF and linearity analysis on Heterojunction‐free GaN layer FINFET through visual technology computer‐aided design (TCAD) device simulator is been illustrated. The influence of varying the Finwidth's of the device on numerous RF parameters like drain current, transconductance (gm), output conductance (gd), gate capacitances(Cgd and Cgs), cut‐off frequency (fT) are studied. And also, the impact of varying the Finwidth's of the device on the numerous linearity parameters like gm2, gm3, VIP3, IIP3, 1 dB compression point were also studied. It is been observed that the higher Finwidth value is more worthy for radio frequency integrated circuit (RFIC) applications.

Dependence of process damage on GaN channel thickness in AlGaN/GaN high-electron-mobility transistors with back-barrier layers

In this study, AlGaN/GaN high-electron-mobility transistors with 65 and 38 nm channel layers and back-barrier layers were fabricated. The isolation process resulted in damage related to the thickness of the channel layer, which deteriorated properties such as sheet resistance R sh and transconductance gm. These were attributed to the surface oxidation of the AlGaN barrier, and the simulation results showed that the channel layer thickness changed the dependence of R sh on the trap level density; however, the calculated changes were smaller than the observed changes. In the range of gate lengths we produced, suppression of the short-channel effect by the back barrier layer was confirmed. However, no significant change in the channel layer thickness was observed.

Common Source Amplifier and Ring Oscillator Circuit Performance Optimization Using Multi-Bridge Channel FETs

In this paper the DC, analog/RF device and circuit applications of nanosheet (NS) FET is performed. To enhance power performance co-optimization geometry parameters like NS width (NSW) and NS thickness (NSH) are varied for high performance (HP) and low power (LP) applications. A rise in 1.47x in I ON and a rise of 5.8x in I OFF is noticed with increase in NSH due to enlarged effective width (W eff). In addition, a rise of 3.8x in I ON and a fall of 76.4% in I OFF is noticed with higher NSW. Larger the NSW ensures better transconductance (gm), transconductance generation factor (TGF), cut-off frequency (f T), gain-band width product (GBW), transconductance frequency product (TFP), and intrinsic delay (τ). The optimized supply voltage (V DD) for maximum voltage gain of common source (CS) amplifier and 3 stage ring oscillators (RO) with varied NSW is performed. Moreover, the impact of number of stages (N) of 3 stage RO for better frequency of oscillations (f OSC) is studied towards high frequency circuit applications.

N-Type Organic Electrochemical Transistors with High Transconductance and Stability

An n-type conjugated polymer based on diazaisoindigo (AIID) and fluorinated thiophene units is introduced. Combining the strong electron-accepting properties of AIID with backbone fluorination produced gAIID-2FT, leading to organic electrochemical transistors (OECTs) with normalized values of 4.09 F cm–1 V–1 s–1 and a normalized transconductance (gm,norm) of 0.94 S cm–1. The resulting OECTs exhibit exceptional operational stability and long shelf-life in ambient conditions, preserving 100% of the original maximum drain current after over 3 h of continuous operation and 28 days of storage in the air. Our work highlights the advantages of integrating strong electron acceptors with donor fluorination to boost the performance and stability of n-type OECTs.

The Integration of Reference Electrode for ISFET Ion Sensors Using Fluorothiophenol-Treated rGO

Ion-sensitive field-effect transistors (ISFETs) detect specific ions in solutions that enable straightforward, fast, and inexpensive sensors compared to other benchtop equipment. However, a conventional reference electrode (RE) such as Ag/AgCl is limited on the miniaturization of the sensor. We introduce reduced graphene oxide (rGO), which serves as a new RE, when fluorinated (F-rGO) using fluorothiophenol through the π-π interaction. The circular RE is integrated between a fabricated microscale two-channel ISFET, which is capable of detecting two kinds of ions on an indium tin oxide (ITO) thin-film substrate, using the photolithography process. F-rGO bound to this circular region to function as an RE in the ISFETs sensor, which operated stably in solution and showed a relatively high transconductance (gm) value (1.27 mS), low drift characteristic (3.2 mV), and low hysteresis voltage (±0.05 mV). It detected proton (H+) ions in a buffer solution with high sensitivity (67.1 mV/pH). We successfully detected Na+ (62.1 mV/dec) and K+ (57.6 mV/dec) ions in human patient urine using a two-channel ISFET with the F-rGO RE. The F-rGO RE will be a suitable component in the fabrication of low-cost, mass-produced, and disposable ISFETs sensors.

Enhancement Performance of High Electron Mobility Transistor (HEMT) Based on Dimensions Downscaling

This paper aims to enhance the performance of the High Electron Mobility Transistor (HEMT) according to downscaling dimensions based on the electrical properties and semiconductor materials (GaN, Si3N4, ALGaN and Si). This is to solve difficulties with reducing dimensions and ensuring HEMT has the highest performance possible. This goal was met when the physical scaling restrictions of channel diameters for different HEMTs were concurrently shrunk without compromising their performance. A simula-tion study was done using four variable factors (length, width, of the channel and length, width of the source and drain). Three electrical characteristics were used to assess the impact of altering dimensions on the performance of each kind of HEMT: threshold voltage Vt, ON-state/OFF-state current (ION/IOFF) ratio, and transconductance gm. To conduct experimental simulations under the specified situation, the well-known Silvaco TCAD simulation tool was used. The acquired simulation results revealed that the optimum performance for the downscaling device was achieved at the channel length of 1.6μm, the channel width of 0.3μm, the length of source and drain is 0.4μm and finally the width of source and drain is 0.05 μm.

Over 10W/mm High Power Density AlGaN/GaN HEMTs With Small Gate Length by the Stepper Lithography for Ka-Band Applications

This study reports AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated by the Stepper Lithography on a 4-inch wafer for Ka-Band applications. Small gate length (LG) of 100 nm was achieved through a 2-Step Photolithography Process and the gate region of the AlGaN/GaN HEMT was defined by using two lithography steps to form gamma-shaped gates. The 4-inch AlGaN/GaN HEMT wafer demonstrated high electrical performance uniformity with respect to the maximum drain-source current density (IDSS), the peak extrinsic output transconductance (Gm), and the threshold voltage (Vth). At <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{ V}}_{\mathrm{ DS}}\,\,=$ </tex-math></inline-formula> 20 V, the AlGaN/GaN HEMT exhibits an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{ I}}_{\mathrm{ DSS}}$ </tex-math></inline-formula> of 1004.2 mA/mm, a Gm value of 363.6 mS/mm, a maximum output power density (POUT(MAX)) of over 10 W/mm, and a power gain of 8.8 dB with a maximum 51.1% Power-added efficiency (PAE) at 28 GHz in Continuous Wave (CW) mode. The results show the potential of AlGaN/GaN HEMT fabrication with high yield and outstanding RF performance using Stepper Lithography for 5G applications.

Design and Performance Optimization of Junctionless Bottom Spacer FinFET for Digital/Analog/RF Applications at Sub-5nm Technology Node

This article for the first time reports the design and performance optimization of Junctionless (JL) Bottom spacer (BSP) FinFET. Initially to get the desired value of workfunction () and fin thickness (Tfin) for analog/RF analysis, the optimization of these parameters has been done by considering several values. It has been noticed that the increase in and reduction in Tfin can lead to better electrical performance with suppressed short channel effects (SCE). Further, it is also observed that reduction in bottom spacer height (HBSP) can fetch enhanced analog/RF performance considering the improvement noticed in transconductance (gm), intrinsic gain (AV), transconductance generation factor (TGF), cutoff frequency (fT), and Gain frequency product (GFP). Moreover, when the bottom spacer dielectric permittivity (KBSP) is increased from 3.9 to 22, it has been found that the analog/RF performance degrades significantly.

UTBB FD-SOI MOSFET with SELBOX in DTMOS Configuration

Abstract— For the first time, Ultra-Thin Body and Buried Oxide Fully Depleted Silicon-On-Insulator (UTBB FDSOI) n-channel with Dynamic Threshold MOS configuration (DTMOS) using the SELBOX (Selective Buried OXide) substrate will be analyzed. The drain and substrate current, transconductance (gm) and Subthreshold Slope (SS) will be compared in the DTMOS mode and the standard biasing configuration for different gap width (WGAP) of SELBOX. Additionally, the output conductance and the transconductance gain also studied through numerical simulations. The results indicate that the SELBOX structure in DTMOS mode is competitive candidates for analog applications.

The effect of post-metal annealing on DC and RF performance of AlGaN/GaN HEMT

The effects of gate post-metal annealing (PMA) on the DC and RF characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The unannealed and post gate-metal annealed AlGaN/GaN HEMTs were fully fabricated using NANOTAM’s 0.5 μm gate length technology. PMA was performed at 450 °C for 10 min in nitrogen ambient for one of the wafers. The main focus was the effect of PMA on the electrical performance of HEMTs, including gate resistivity, transconductance, small-signal gain, output power (Pout), and threshold voltage (Vth) shift. It is achieved that HEMT with PMA has a gain of 18.5 dB, while HEMT without PMA shows a small-signal gain of 21.8 dB, as the PMA process increases the gate resistance (Rg) and decreases the transconductance (gm). The large-signal performance of the sample with PMA is better than the one without PMA, having an increase of 1.4 W/mm in Po ut from 20.9 W to 24.4 W. The transistor with PMA also demonstrates a reliable gate performance and stable Vth, and the wafer exhibits better uniformity.

Study of ambipolar properties of organic-inorganic CH3NH3PbI3 perovskite for vertical field effect transistor

A vertical field effect transistor (VFET) with short channel length of 120 nm, fabricated using organic-inorganic perovskite (CH3NH3PbI3) material shows the ambipolar properties and switches from P mode to N mode or vice versa, just by changing the polarity of applied bias. The operating voltage is as low as 0.5 V, which allows it to be integrated with solar cell devices and hence having the possibility of battery less mobile gadgets. To ensure the quality of VFET with CH3NH3PbI3 as a channel length, different parameters have been extracted. The transistor efficiency (TE), mobility (μ p), and transconductance (gm) in P mode, have been estimated as 14 V−1, 1.5 cm2 V−1 s−1 and 500 ± 150 μS, respectively. For N mode, these parameters have been found to be as 4 V−1, 0.97 cm2V−1 s−1 and 60 ± 10 μS respectively. The hole and electron densities are found to be as ∼1016 cm−3 and ∼1014 cm−3 respectively which confirm the ambipolar nature of CH3NH3PbI3.