Intrinsic Mobility Research Articles

Electron-phonon drag enhancement of transport properties from a fully coupled ab initio Boltzmann formalism

We present a combined treatment of the non-equilibrium dynamics and transport of electrons and phonons by carrying out \textit{ab initio} calculations of the fully coupled electron and phonon Boltzmann transport equations. We find that the presence of mutual drag between the two carriers causes the thermopower to be enhanced and dominated by the transport of phonons, rather than electrons as in the traditional semiconductor picture. Drag also strongly boosts the intrinsic electron mobility, thermal conductivity and the Lorenz number. Impurity scattering is seen to suppress the drag-enhancement of the thermal and electrical conductivities, while having weak effects on the enhancement of the Lorenz number and thermopower. We demonstrate these effects in \textit{n}-doped 3C-SiC at room temperature, and explain their origins. This work establishes the roles of microscopic scattering mechanisms in the emergence of strong drag effects in the transport of the interacting electron-phonon gas.

Evaluations of nonlocal electron-phonon couplings in tetracene, rubrene, and C10−DNBDT−NW based on density functional theory

In organic molecular semiconductors (OSCs), fluctuation of transfer integrals originating from thermally induced molecular vibrations is suggested to cause large scatterings of carriers, and to be a most important factor for the suppression of their carrier mobility. The intrinsic carrier mobility under such a fluctuation of transfer integrals is calculated using the transient localization theory, in which the estimation of transfer-integral fluctuation depending on each OSC is indispensable. In the present study, we provide a methodology to evaluate nonlocal electron-phonon couplings in OSCs using the density functional theory, which enables us to evaluate precisely the fluctuation magnitude of transfer integrals. Our method is based upon the combination of the frequency correction to reduce numerical inaccuracies in normal-mode frequencies, the extraction of tight binding parameters using maximally localized Wannier functions, and the explicit consideration of anharmonicity of phonons. We apply this method to classical OSCs, tetracene and rubrene, and a recently developed high-mobility OSC, $3,11\text{\ensuremath{-}}\text{didecyl-dinaphtho}[2,3\text{\ensuremath{-}}d:2\ensuremath{'},3\ensuremath{'}\text{\ensuremath{-}}d\ensuremath{'}]\mathrm{benzo}[1,2\text{\ensuremath{-}}b:4,5\text{\ensuremath{-}}b\ensuremath{'}]\mathrm{dithiophene}$ $({\mathrm{C}}_{10}\text{\ensuremath{-}}\mathrm{DNBDT}\text{\ensuremath{-}}\mathrm{NW})$. We succeeded in identifying the low-frequency vibrations dominating the fluctuation of transfer integrals at room temperature, which we consider to be the main factors to limit the intrinsic mobility.

Prediction of Intrinsic Charge Mobility for Materials Developments of Organic Semiconductors

Prediction of Intrinsic Charge Mobility for Materials Developments of Organic Semiconductors

Large Single Crystals of Two-Dimensional π-Conjugated Metal-Organic Frameworks via Biphasic Solution-Solid Growth.

Two-dimensional (2D) π-conjugated metal–organic frameworks (πMOFs) are a new class of designer electronic materials that are porous and tunable through the constituent organic molecules and choice of metal ions. Unlike typical MOFs, 2D πMOFs exhibit high conductivity mediated by delocalized π-electrons and have promising applications in a range of electrical devices as well as exotic physical properties. Here, we develop a growth method that generates single-crystal plates with lateral dimensions exceeding 10 μm, orders of magnitude bigger than previous methods. Synthesis of large single crystals eliminates a significant impediment to the fundamental characterization of the materials, allowing determination of the intrinsic conductivity and mobility along the 2D plane of πMOFs. A representative 2D πMOF, Ni-CAT-1, exhibits a conductivity of up to 2 S/cm, and Hall measurement reveals the origin of the high conductivity. Characterization of crystalline 2D πMOFs creates the foundation for developing electronic applications of this promising and highly diverse class of materials.

Effect of Ga composition on mobility in a-InGaZnO thin-film transistors

Oxide semiconductor TFTs have attracted considerable attention in the recent past due to their excellent mobility, high optical transparency in the visible region, and most importantly their fabrication process at low-temperature. However, charge trapping formation in the gate dielectric and the interfaces in such oxide TFTs leads to serious issues such as their operational stability and reliability. Understanding the charge trapping mechanism is therefore of utmost importance to identify the root cause of the aforesaid problems. In this report, we present a detailed study on the charge trapping and dynamic charge transport of a-IGZO TFTs by examining microsecond fast IV (FIV), pulse IV (PIV), and transient IV measurements. The a-IGZO TFTs have designed and fabricated with various Ga compositions (0, 0.14 and 0.22). It was observed that the charge trapping in the a-IGZO TFT is reliant on the sweeping time and the carrier mobility measured using the FIV technique was found to be higher than that obtained from the conventional DC IV measurement. Mobility values () was also measured through the PIV technique and are found to be approximately 10%, 16%, and 21% lower than the intrinsic mobility values. Temperature-dependent study reveals that the intrinsic mobility values (18.45, 16.1 and 12.03 cm2 V−1 s−1) are higher than the pulse mobility values for various Ga compositions (0, 0.14 and 0.22) at higher temperature (175 °C) probably due to the formation of free carriers. Suitable optimization of process parameters of a-IGZO TFTs can therefore enhance the device stability and reliability characteristics leading to their potential utilization in flexible and stretchable electronic devices, sensors & detectors and biomedical devices.

(Invited) Si-Cap-Free Low-DIT SiGe Gate Stack for High-Performance pFETs

As the continuous physical device scaling is facing increasing challenges in today’s CMOS technology, introduction of high mobility channel material has further increased its potential value as performance booster. Low-Ge-content SiGe is the leading candidate for p-channel devices, as it is process-compatible with state-of-the-art Si CMOS fabrication platform and requires no strain relaxed buffer layer. In order to benefit from the high intrinsic carrier mobility at a low VDD operation, an efficient SiGe channel passivation with low interface state densities (Dit) needs to be developped. However, the presence of GeO is known to increase Dit [1]. One of the effective passivation schemes for SiGe-based channel surface uses an epitaxially-grown ultrathin Si cap [2]. It suppresses the formation of GeO and enables to fabricate a high-k/SiO2 gate stack equivalent to the one in Si devices. The outstanding improvement achieved with this approach was previously highlighted on pure Ge channel devices, where the formation of GeO is inevitable without the use of Si-cap [3]. On the other hand, it poses some concerns such as EOT penalty and process controllability, making the Si-cap-free route the desired option as long as the interface and oxide bulk trap densities can be kept under control. In this contribution, we will review our recent studies towards the realization of a low-Dit Si-cap-free SiGe gate stack [4]. Selective GeO scavenging from Si1-xGexOy interface layer was previously reported as the key process to reduce Dit of SiGe gate stack [1]. Wostyn et al., demonstrated on Si0.75Ge0.25 that the annealing of chemical oxide in inert ambient (i.e. H2) reduces GeO in Si1-xGexOy IL thanks to the conversion of the thermally-unstable GeO into SiO [5]. A MOS capacitor experiment confirmed a clear Dit reduction by H2 anneal, although at an increased EOT. Additional NH3 anneal on IL was found to further reduce the Dit down to 5×1011 cm-2eV-1 while cancelling out the H2-anneal-induced EOT increase (EOT=10.1 Å). We also found that the metal gate deposition process has a strong impact on Dit even for the same metal. While the PVD W/TiN led to low Dit and EOT, both of them increased as the PVD was changed to ALD (or ALD followed by CVD) process. This can be explained by the PVD-TiN-induced additional GeO scavenging from IL [6] and/or oxygen diffusion from ALD-based metal to IL through HfO2 inducing GeO formation. A nitridation of HfO2 was found to suppress the negative impact from ALD-based metal electrode. XPS confirmed that the significant Dit reduction coincides with the nitridation of HfO2. By replacing the HfO2 with other dielectrics in which lower oxygen diffusivity is expected such as SiO2, the Dit of SiGe gate stack became insensitive to the metal deposition process and nitridation, indicating that the high oxygen diffusivity of the HfO2 layer was, together with the GeO formation, the root cause of the process-sensitive Dit. These results emphasize the importance of the oxygen depth profile control for the realization of a low-Dit SiGe gate stack.

(Plenary) The Revival of Compound Semiconductors and How They Will Change the World in a 5G/6G Era

Compound semiconductor devices have always intrigued the semiconductor industry due to their high intrinsic mobilities and the heterostructure engineering enabled by those materials. While CMOS has been the vehicle pushing the industry to ever smaller devices, better performance and of course reduced cost, the unique properties of compound semiconductor devices are finding renewed interest in an era where an increasing amount of data is being sent around, stored and analyzed. While several applications like photonics, high-power electronics and image sensors also benefit from enabling a variety of III-V materials and devices, specifically, in the RF Front-End Modules of 5G radio chips [1], these materials allow to address the challenges related to speed, efficiency and output power needed for this next generation wireless communication standard. And while 5G is in full deployment, with first addressing the sub-6GHz frequency bands and in a later phase the mm-wave frequency bands, first publications are already appearing on 6G, where even higher frequencies (beyond > 100GHz) will be targeted [2].GaN [3] and InP-based devices [4] have a clear performance advantage over Si CMOS and SiGe HBT/BICMOS, but their lower integration potential, still restricted to smaller size substrates and lab-like processing today, is one of the key limitations for adopting those technologies for high-volume 5G and 6G applications. Upscaling those devices to a 200mm/300mm Si platform will be a first step to improve yield and maturity and increase complexity. In a second phase, upscaling and maturing these technologies will allow to co-integrate these devices, usually quite dissimilar to CMOS, with advanced Si technology nodes and provide a fully integrated heterogeneous system.In this talk, we will review the status and progress toward integrating these devices on a CMOS-compatible platform.

Engineering Surface N‐Vacancy Defects of Ultrathin Mesoporous Carbon Nitride Nanosheets as Efficient Visible‐Light‐Driven Photocatalysts

Graphitic carbon nitride (GCN) has become an attractive photocatalyst for solar energy conversion, but the photocatalytic activity of GCN is still limited by the extremely fast electron–hole recombination. Herein, a defective ultrathin mesoporous graphitic carbon nitride (DUMCN) photocatalyst with high specific surface area and mesoporous structure is fabricated through a facile three‐step heat‐treatment strategy, which reduces the distance of bulk photogenerated carriers to the surface, resulting in efficient adsorption and diffusion of reactants and products, and exposing adequate surface active sites. Moreover, suitable N‐vacancy defects are formed via high‐temperature surface hydrogenation, which can extend light absorption and produce ultra‐high intrinsic carrier mobility, and further increase the active sites. The photocatalytic hydrogen production rate is up to 13.63 mmol h−1 g−1 under visible light in the triethanolamine solution and 33.5 μmol h−1 g−1 for overall water splitting, which is much higher than that of bulk graphitic carbon nitride (BCN) structures. Density functional theory (DFT) calculations further reveal the effect of surface defects on the band structure for promoting the spatial charge separation. This facile strategy may offer new insights into designing other ultrathin mesoporous semiconductor photocatalysts with high performance.

Thiophene-Bridged Donor-Acceptor sp2 -Carbon-Linked 2D Conjugated Polymers as Photocathodes for Water Reduction.

Photoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene-bridged donor-acceptor-based 2D sp2 -carbon-linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron-accepting building block 2,3,8,9,14,15-hexa(4-formylphenyl) diquinoxalino[2,3-a:2',3'-c]phenazine (HATN-6CHO) and the first electron-donating linker 2,2'-([2,2'-bithiophene]-5,5'-diyl)diacetonitrile (ThDAN) provides the 2D CCP-HATNThDAN (2D CCP-Th). Compared with the corresponding biphenyl-bridged 2D CCP-HATN-BDAN (2D CCP-BD), the bithiophene-based 2D CCP-Th exhibits a wide light-harvesting range (up to 674nm), a optical energy gap (2.04eV), and highest energy occupied molecular orbital-lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP-Th a promising candidate for PEC water reduction. As a result, 2D CCP-Th presents a superb H2 -evolution photocurrent density up to ≈7.9 µA cm-2 at 0V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09-6.0 µA cm-2 ). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H2 .

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools.

Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of ~2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal β-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.

Charge and Thermoelectric Transport in Polymer-Sorted Semiconducting Single-Walled Carbon Nanotube Networks.

Understanding the charge transport mechanisms in chirality-selected single-walled carbon nanotube (SWCNT) networks and the influence of network parameters is essential for further advances of their optoelectronic and thermoelectric applications. Here, we report on charge density and temperature-dependent field-effect mobility and on-chip field-effect-modulated Seebeck coefficient measurements of polymer-sorted monochiral small-diameter (6,5) (0.76 nm) and mixed large-diameter SWCNT (1.17-1.55 nm) networks (plasma torch nanotubes, RN) with different network densities and length distributions. All untreated networks display balanced ambipolar transport and electron-hole symmetric Seebeck coefficients. We show that charge and thermoelectric transport in SWCNT networks can be modeled by the Boltzmann transport formalism, incorporating transport in heterogeneous media and fluctuation-induced tunneling. Considering the diameter-dependent one-dimensional density of states (DoS) of the SWCNTs composing the network, we can simulate the charge density and temperature-dependent Seebeck coefficients. Our simulations suggest that scattering in these networks cannot be described as simple one-dimensional acoustic and optical phonon scattering as for single SWCNTs. Instead the relaxation time is inversely proportional to energy (τ ∝ (E - EC)s, s = -1, EC being the energy of the first van Hove singularity), presumably pointing toward the more two-dimensional character of scattering events and the necessity to include scattering at the SWCNT junctions. Finally, our observation of higher power factors in trap-free, 1,2,4,5-tetrakis(tetramethylguanidino)benzene-treated (6,5) networks than in the RN networks emphasizes the importance of chirality selection to tune the width of the DoS. To benefit from both higher intrinsic mobilities and a large thermally accessible DoS, we propose trap-free, narrow DoS distribution, large-diameter SWCNT networks for both electronic and thermoelectric applications.

Recent progress in contact, mobility, and encapsulation engineering of InSe and GaSe

AbstractThe field of two‐dimensional (2D) materials has stimulated considerable interest in the scientific community. Owing to quantum confinement in one direction, intriguing properties have been reported in 2D materials that cannot be observed in their bulk form. The advent of semiconducting 2D materials with a broad range of electronic properties has provided fascinating opportunities to design and configure next‐generation electronics. One such emerging class is the family of III‐VI monochalcogenides, the two prominent members of which are indium selenide (InSe) and gallium selenide (GaSe). In contrast to transition metal dichalcogenides, their high intrinsic mobility and the availability of a direct bandgap at small thicknesses have attracted researchers to investigate the underlying physical phenomena as well as their technological applications. However, the sensitivity of InSe and GaSe to environmental influences has limited their exploitation in functional devices. The lack of methods for their scalable synthesis further hinders the realization of their devices. This review article outlines recent advancements in the synthesis and understanding of the charge transport properties of InSe and GaSe for their integration into technological applications. A detailed summary of the improvements in the device structure by optimizing extrinsic factors such as bottom substrates, metal contacts, and device fabrication schemes is provided. Furthermore, various encapsulation techniques that have been proven effective in preventing the degradation of InSe and GaSe layers under ambient conditions are thoroughly discussed. Finally, this article presents an outlook on future research ventures with respect to ongoing developments and practical viability of these materials.image

Nonideal double-slope effect in organic field-effect transistors

With the development of device engineering and molecular design, organic field effect transistors (OFETs) with high mobility over 10 cm2·V−1·s−1 have been reported. However, the nonideal double-slope effect has been frequently observed in some of these OFETs, which makes it difficult to extract the intrinsic mobility OFETs accurately, impeding the further application of them. In this review, the origin of the nonideal double-slope effect has been discussed thoroughly, with affecting factors such as contact resistance, charge trapping, disorder effects and coulombic interactions considered. According to these discussions and the understanding of the mechanism behind double-slope effect, several strategies have been proposed to realize ideal OFETs, such as doping, molecular engineering, charge trapping reduction, and contact engineering. After that, some novel devices based on the nonideal double-slope behaviors have been also introduced.

Ultrahigh carrier mobility of penta-graphene: A first-principle study

Within the formalism of density functional theory and using the concept of effective mass approximation, the electron-acoustic phonon scattering principle along with the deformation potential theory of Bardeen and Shockley, we have investigated the intrinsic charge carrier mobility of penta-graphene. The electron mobility of penta-graphene is significantly large compared to hole mobility and it is reasonably higher than other novel two-dimensional materials e.g. penta-X 2 C (X = P, As, Sb), Si-based pentagonal monolayer (SiX, X = B, C, N), penta-stanene monolayer and CaP 3 which possess the highest carrier (electron) mobility among phosphorene derivatives. This high carrier mobility originates from the low effective mass, low deformation potential and high stiffness constant of this material. As our main focus is to investigate the carrier mobility which depends on band edges, a detailed study about orbital contribution to the electronic states in the vicinity of band edges has been carried out. The intrinsic wide band gap and ultrahigh carrier mobility show the possible signature of using it in the fabrication of microelectronic devices, mainly in FETs and logic circuits and in optoelectronic devices . • The electron mobility of PG is significantly large compared to hole mobility. • Ultrahigh mobility originates from low effective mass and high stiffness constant. • The electron mobility of unstrained PG is 22.74 × 10 3 cm 2 /V at 300 K. • The electron mobility of PG varies from 11.72 to 40.90 × 10 3 cm 2 /V for +4% to −4% strain at 300 K. • PG may be suitable for microelectronics applications.

A Curved Graphene Nanoribbon with Multi-Edge Structure and High Intrinsic Charge Carrier Mobility

Structurally well-defined graphene nanoribbons (GNRs) have emerged as highly promising materials for the next-generation nanoelectronics. The electronic properties of GNRs critically depend on their edge topologies. Here, we demonstrate the efficient synthesis of a curved GNR (cGNR) with a combined cove, zigzag, and armchair edge structure, through bottom-up synthesis. The curvature of the cGNR is elucidated by the corresponding model compounds tetrabenzo[a,cd,j,lm]perylene (1) and diphenanthrene-fused tetrabenzo[a,cd,j,lm]perylene (2), the structures of which are unambiguously confirmed by the X-ray single-crystal analysis. The resultant multi-edged cGNR exhibits a well-resolved absorption at the near-infrared (NIR) region with a maximum peak at 850 nm, corresponding to a narrow optical energy gap of ∼1.22 eV. Employing THz spectroscopy, we disclose a long scattering time of ∼60 fs, corresponding to a record intrinsic charge carrier mobility of ∼600 cm2 V-1 s-1 for photogenerated charge carriers in cGNR.

The electric field at the hole-injecting metal/organic interface controls the bias dependence of the current–voltage hole mobility

Based upon the room temperature current–voltage data of some published organic diode structures the unique phenomenon of the decreasing hole mobility, μ, with the increasing applied electric field, E a, is interpreted. The measurable quantity, the hole drift mobility μ d is formulated in terms of E a and the electric field at the hole injecting metal/organic interface, E int, dependent algebraic function multiplied by the intrinsic hole mobility, μ max that is organic morphology dependent but E a independent scaling factor. On account that the intrinsic mobility, μ max, is uncoupled from both E a and E int it is shown that the origin of the negative field hole mobility effect occurs due to E int, that is a linear function of E a. The bias and the space distribution of the internal organic electric field, E, as well as the free hole density, p, for poly(3-hexylthiophene) is calculated in detail. Depending on the organic layer morphology the internal electric field may exhibit, at the particular value of E a, a deep well in the vicinity of the hole injecting metal/organic interface. Then the strong peak of the free hole density exists there the effect of which is spreading some 10 nm into the organic. If E int happens to be E a independent constant, then from the resulting space charge limited current density, the increasing hole drift mobility, μ d, with the increasing applied electric field, E a, is deduced. The published current–voltage data of two distinct metal-substituted phthalocyanine thin films provide an additional confirmation of the described formalism.

Simultaneous defect passivation and hole mobility enhancement of perovskite solar cells by incorporating anionic metal-organic framework into hole transport materials

Originated from the defects of hybrid halide perovskite and the intrinsic low hole mobility of hole transport materials (HTM), the perovskite degradation and interface carrier recombination hampered the stability and power conversion efficiency (PCE) of PSCs. Herein, we construct a dual-functional layer HTM-FJU-17 by incorporating the (Me2NH2)+-encapsulated indium-based anionic metal-organic framework (FJU-17) as a “capsule” into HTM. The FJU-17 capsule would passivate the organic cation vacancies with releasing (Me2NH2)+ ion, while its anionic framework can stabilize the positively charged oxidized HTM to enhance hole mobility. As a result, PSCs exhibit suppressed charge recombination with PCE improvement from 18.32% to 20.34%, and stable device is obtained with 90% retaining of the original PCE after 1000 h in ambient condition. This work demonstrates the promising potential of using the dual-functional layer based on the large family of anionic MOFs/HTMs to manufacture PSC devices with high performance and simplified preparation processes.

Electro-thermal co-design of β -(AlxGa1-x)2O3/Ga2O3 modulation doped field effect transistors

Ultra-wide bandgap β-gallium oxide (Ga2O3) devices are of considerable interest with potential applications in both power electronics and radio frequency devices. However, current Ga2O3 device technologies are limited by the material's low intrinsic electron mobility and thermal conductivity. The former problem can be addressed by employing modulation-doped β-(AlxGa1−x)2O3/Ga2O3 heterostructures in the device architecture. In this work, (AlxGa1−x)2O3/Ga2O3 modulation-doped field effect transistors (MODFETs) have been investigated from a thermal perspective. Thermoreflectance thermal imaging was used to characterize the self-heating of the MODFETs. The (Al0.18Ga0.82)2O3 thermal conductivity (3.1–3.6 W/mK) was determined using a frequency domain thermoreflectance technique. Electro-thermal modeling was used to discern the effect of design parameters such as substrate orientation and channel length on the device self-heating behavior. Various thermal management schemes were evaluated using the electro-thermal device model. From an electro-thermal co-design perspective, the improvement in electrical performance followed by the mitigation of self-heating was also studied. For example, by employing a Ga2O3-on-SiC composite wafer, which was fabricated in this work, a 50% increase in power handling capability can be achieved as compared to a homoepitaxial device. Furthermore, flip-chip heterointegration and double-sided cooling approaches can lead to more than 2× improvement in the power handling capability. Using an augmented double-sided cooling design that includes nanocrystalline diamond passivation, a 5× improvement in the power handling capability can be accomplished, indicating the potential of the technology upon implementation of a suitable thermal management scheme.

A Method for Series-Resistance-Immune Extraction of Low-Frequency Noise Parameters in Nanoscale MOSFETs

This article presents a new methodology for the extraction of low-frequency noise (LFN) or random telegraph noise (RTN) parameters, such as the gate oxide interface trap density, N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> , and the mobility fluctuations factor, Ω, without the influence of the source/drain series resistance, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sd</sub> . The method utilizes the Y-function - which is immune to any first-order degradation, including the series resistance-as well as the intrinsic mobility degradation factors θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,0</sub> and θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The proposed extraction technique is first demonstrated through numerical calculations and then applied on experimental results of n-channel short length FinFETs. It is shown that if the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sd</sub> impact is not accounted for, the extracted LFN parameters through the classic carrier number fluctuations (CNF) with correlated mobility fluctuations (CMF) model can lead to significant extraction errors. This mainly concerns the correlated mobility factor Ω, which may be strongly underestimated, but also the extraction of the trap density N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> .

High-performance integrated graphene electro-optic modulator at cryogenic temperature

AbstractHigh-performance integrated electro-optic modulators operating at low temperature are critical for optical interconnects in cryogenic applications. Existing integrated modulators, however, suffer from reduced modulation efficiency or bandwidth at low temperatures because they rely on tuning mechanisms that degrade with decreasing temperature. Graphene modulators are a promising alternative because graphene’s intrinsic carrier mobility increases at low temperature. Here, we demonstrate an integrated graphene-based electro-optic modulator whose 14.7 GHz bandwidth at 4.9 K exceeds the room temperature bandwidth of 12.6 GHz. The bandwidth of the modulator is limited only by high contact resistance, and its intrinsic RC-limited bandwidth is 200 GHz at 4.9 K.