Showing papers on "Induced high electron mobility transistor published in 2017"

N-Polar GaN Cap MISHEMT With Record Power Density Exceeding 6.5 W/mm at 94 GHz

Abstract: A novel N-Polar GaN cap (MIS)high electron mobility transistor demonstrating record 6.7-W/mm power density with an associated power-added efficiency of 14.4% at 94 GHz is presented. This state-of-the-art power performance is enabled by utilizing the inherent polarization fields of N-Polar GaN in combination with a 47.5-nm in situ GaN cap layer to simultaneously mitigate dispersion and improve access region conductivity. These excellent results build upon past work through the use of optimized device dimensions and a transition from a sapphire to a substrate for reduced self-heating.

Black Phosphorus N-Type Field-Effect Transistor with Ultrahigh Electron Mobility via Aluminum Adatoms Doping.

Abstract: High-performance black phosphorus n-type field-effect transistors are realized using Al adatoms as effective electron donors, which achieved a record high mobility of >1495 cm2 V-1 s-1 at 260 K. The electron mobility is corroborated to charged-impurity scattering at low temperature, whilst metallic-like conduction is observed at high gate bias with increased carrier density due to enhanced electron-phonon interactions at high temperature.

The Nature of Electron Mobility in Hybrid Perovskite CH3NH3PbI3.

Abstract: CH3NH3PbI3 is one of the most promising candidates for cheap and high-efficiency solar cells. One of its unique features is the long carrier diffusion length (>100 μm), but its carrier mobility is rather modest. The nature of the mobility is unclear. Here, using nonadiabatic wave function dynamics simulations, we show that the random rotations of the CH3NH3 cations play an important role in the carrier mobility. Our previous work showed that the electron and hole wave functions were localized and spatially separated due to the random orientations of the CH3NH3 cations in the tetragonal phase. We find that the localized carriers are able to conduct random walks due to the electrostatic potential fluctuation caused by the CH3NH3 random rotations. The calculated electron mobilities are in the experimentally measured range. We thus conclude that the carrier mobility of CH3NH3PbI3 is likely driven by the dynamic disorder that causes the fluctuation of the electrostatic potential.

High Temperature Terahertz Detectors Realized by a GaN High Electron Mobility Transistor.

Abstract: In this work, a high temperature THz detector based on a GaN high electron mobility transistor (HEMT) with nano antenna structures was fabricated and demonstrated to be able to work up to 200 °C. The THz responsivity and noise equivalent power (NEP) of the device were characterized at 0.14 THz radiation over a wide temperature range from room temperature to 200 °C. A high responsivity Rv of 15.5 and 2.7 kV/W and a low NEP of 0.58 and 10 pW/Hz0.5 were obtained at room temperature and 200 °C, respectively. The advantages of the GaN HEMT over other types of field effect transistors for high temperature terahertz detection are discussed. The physical mechanisms responsible for the temperature dependence of the responsivity and NEP of the GaN HEMT are also analyzed thoroughly.

Enhanced electron mobility at the two-dimensional metallic surface of BaSnO3 electric-double-layer transistor at low temperatures

Abstract: Wide-bandgap oxides exhibiting high electron mobility hold promise for the development of useful electronic and optoelectronic devices as well as for basic research on two-dimensional electron transport phenomena A perovskite-type tin oxide, BaSnO3, is currently one of such targets owing to distinctly high mobility at room temperature The challenge to overcome towards the use of BaSnO3 thin films in applications is suppression of dislocation scattering, which is one of the dominant scattering origins for electron transport Here, we show that the mobility of the BaSnO3 electric-double-layer transistor reaches 300 cm2 V−1 s−1 at 50 K The improved mobility indicates that charged dislocation scattering is effectively screened by electrostatically doped high-density charge carriers We also observed metallic conduction persisting down to 2 K, which is attributed to the transition to the degenerate semiconductor The experimental verification of bulk-level mobility at the densely accumulated surface sheds m

Tunable Mobility in Double-Gated MoTe2 Field-Effect Transistor: Effect of Coulomb Screening and Trap Sites

Abstract: There is a general consensus that the carrier mobility in a field-effect transistor (FET) made of semiconducting transition-metal dichalcogenides (s-TMDs) is severely degraded by the trapping/detrapping and Coulomb scattering of carriers by ionic charges in the gate oxides. Using a double-gated (DG) MoTe2 FET, we modulated and enhanced the carrier mobility by adjusting the top- and bottom-gate biases. The relevant mechanism for mobility tuning in this device was explored using static DC and low-frequency (LF) noise characterizations. In the investigations, LF-noise analysis revealed that for a strong back-gate bias the Coulomb scattering of carriers by ionized traps in the gate dielectrics is strongly screened by accumulation charges. This significantly reduces the electrostatic scattering of channel carriers by the interface trap sites, resulting in increased mobility. The reduction of the number of effective trap sites also depends on the gate bias, implying that owing to the gate bias, the carriers are...

Observation of abnormal mobility enhancement in multilayer MoS2 transistor by synergy of ultraviolet illumination and ozone plasma treatment

Abstract: Mobility engineering through physical or chemical process is a fruitful approach for the atomically-layered two-dimensional electronic applications. Unfortunately, the usual process with either illumination or oxygen treatment would greatly deteriorate the mobility in two-dimensional MoS2 field-effect transistor (FET). Here, in this work, we report that the mobility can be abnormally enhanced to an order of magnitude by the synergy of ultraviolet illumination (UV) and ozone plasma treatment in multilayer MoS2 FET. This abnormal mobility enhancement is attributed to the trap passivation due to the photo-generated excess carriers during UV/ozone plasma treatment. An energy band model based on Schottky barrier modulation is proposed to understand the underlying mechanism. Raman spectra results indicate that the oxygen ions are incorporated into the surface of MoS2 (some of them are in the form of ultra-thin Mo-oxide) and can further confirm this proposed mechanism. Our results can thus provide a simple approach for mobility engineering in MoS2-based FET and can be easily expanded to other 2D electronic devices, which represents a significant step toward applications of 2D layered materials in advanced cost-effective electronics.

Organic High Electron Mobility Transistors Realized by 2D Electron Gas

Abstract: A key breakthrough in inorganic modern electronics is the energy-band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field-effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high-mobility crystalline organic materials. Therefore, there emerges a chance for applying energy-band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy-band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm2 V-1 s-1 , and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy-band engineering, offering a promising way for the step forward of organic electronics.

High electron mobility of β-HgS colloidal quantum dots with doubly occupied quantum states

Abstract: Electron occupation of the lowest electronic state of the conduction band (1Se) of a semiconducting nanocrystal offers numerous opportunities to efficiently utilize the quantization of the colloidal quantum dot. The steady-state electron occupation of the 1Se gives rise to unprecedented electrical, optical, and magnetic properties. We report an electron mobility of ∼1.29 cm2 V−1 s−1 measured in a mercury sulfide (β-HgS) quantum dot field effect transistor (FET), demonstrating the best carrier mobility for the HgS colloidal nanocrystal solid. The high electron mobility of the HgS nanocrystals with the doubly occupied quantum state originates from the efficient ligand exchange from oleylamine to thiocyanate, better carrier hopping via shortened inter-dot-distance, and the packing of nanocrystals by optimized thermal annealing conditions.

Electron driven mobility model by light on the stacked metal–dielectric interfaces

Abstract: An electron mobility enhancement is the very important phenomenon of an electron in the electronic device, where the high electronic device performance has the good electron mobility, which is obtained by the overall electron drift velocity in the electronic material driven potential difference. The increase in electron mobility by the injected high group velocity pulse is proposed in this article. By using light pulse input into the nonlinear microring resonator, light pulse group velocity can be tuned and increased, from which the required output group velocity can be obtained, which can be used to drive electron within the plasmonic waveguide, where eventually, the relative electron mobility can be obtained, the increasing in the electron mobility after adding up by the driven optical fields can be connected to the external electronic devices and circuits, which can be useful for many applications.

Mobility Modulation and Suppression of Defect Formation in Two-Dimensional Electron Systems by Charge-Transfer Management

Abstract: Electron mobility is one of the most-debated key attributes of low-dimensional electron systems emerging at complex oxide heterointerfaces. However, a common understanding of how electron mobility can be optimized in these systems has not been achieved so far. Here, we discuss a novel approach for achieving a systematic increase in electron mobility in polar/nonpolar perovskite interfaces by suppressing the thermodynamically required defect formation at the nanoscale. We discuss the transport properties of electron gases established at interfaces between SrTiO3 and various polar perovskites [LaAlO3, NdGaO3, and (La,Sr)(Al,Ta)O3], allowing for the individual variation of epitaxial strain and charge transfer among these epitaxial interfaces. As we show, the reduced charge transfer at (La,Sr)(Al,Ta)O3/SrTiO3 interfaces yields a systematic increase in electron mobility, while the reduced epitaxial strain has only minor impact. As thermodynamic continuum simulations suggest, the charge transfer across these in...

δ-Doping Effects on Electronic and Energetic Properties of LaAlO3/SrTiO3 Heterostructure: First-Principles Analysis of 23 Transition-Metal Dopants

Abstract: The 2D electron gas (2DEG) formed at the interface between two insulating perovskite oxides such as LaAlO3 and SrTiO3 provides a playground for developing all-oxide electronic devices, though improving the 2DEG mobility is still a great challenge. One possible way of improving the 2DEG mobility is via δ-doping at the heterointerface. As a proof of concept, one recent experiment achieves an ultra-high 2DEG mobility of 73 000 cm2 V−1 s−1 at the LaAlO3/SrTiO3 heterointerface via Mn δ-doping. Here the electronic and energetic properties of δ-doped LaAlO3/SrTiO3 are studied with 23 transition-metal dopants from group 3 to group 10 using first-principles calculations. A clear trend is found for the electron effective mass and interfacial energy change in the δ-doped LaAlO3/SrTiO3 with various dopants, and there exists a trade-off between achieving light effective mass bands and forming energetically favorable structures. It is found that the Fe, Co, Ni, Ru, Rh, Pd, Os, and Ir could also serve as promising candidate dopants to produce light effective mass bands and relatively high energetic stability, in addition to the experimentally confirmed Mn dopant. The findings of this study provide a wide avenue to increase the 2DEG mobility in the LaAlO3/SrTiO3 heterostructure via δ-doping with transition metals.

Enhancing optoelectronic properties of SiC-grown graphene by a surface layer of colloidal quantum dots

Abstract: We report a simultaneous increase of carrier concentration, mobility and photoresponsivity when SiC-grown graphene is decorated with a surface layer of colloidal PbS quantum dots, which act as electron donors. The charge on the ionised dots is spatially correlated with defect charges on the SiC-graphene interface, thus enhancing both electron carrier density and mobility. This charge-correlation model is supported by Monte Carlo simulations of electron transport and used to explain the unexpected 3-fold increase of mobility with increasing electron density. The enhanced carrier concentration and mobility give rise to Shubnikov-de Haas oscillations in the magnetoresistance, which provide an estimate of the electron cyclotron mass in graphene at high densities and Fermi energies up to 1.2 x 10(13) cm(-2) and 400 meV, respectively.

Modelling of capacitance and threshold voltage for ultrathin normally-off AlGaN / GaN MOSHEMT

Abstract: A compact quantitative model based on oxide semiconductor interface density of states (DOS) is proposed for Al0.25Ga0.75N/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT). Mathematical expressions for surface potential, sheet charge concentration, gate capacitance and threshold voltage have been derived. The gate capacitance behaviour is studied in terms of capacitance–voltage (CV) characteristics. Similarly, the predicted threshold voltage (V T) is analysed by varying barrier thickness and oxide thickness. The positive V T obtained for a very thin 3 nm AlGaN barrier layer enables the enhancement mode operation of the MOSHEMT. These devices, along with depletion mode devices, are basic constituents of cascode configuration in power electronic circuits. The expressions developed are used in conventional long-channel HEMT drain current equation and evaluated to obtain different DC characteristics. The obtained results are compared with experimental data taken from literature which show good agreement and hence endorse the proposed model.

The impact of surface-roughness scattering on the low-field electron mobility in nano-scale Si MOSFETs

Abstract: A state-of-the-art simulator for the calculation of low-field mobility in inversion layers is presented in this work that accounts for the collisional broadening of the electronic states via the solution of the Dyson equation for the retarded Green's function. The self-consistent Born approximation is used for the calculation of the self-energy contributions due to Coulomb, surface-roughness, acoustic, and non-polar optical phonon scattering. The simulated mobility results for three generations of MOSFET devices are in agreement with the experimental data. At nanoscale dimensions, surface-roughness scattering dominates the collisional broadening of the states and the renormalization of the spectrum.

First experimental observation of channel thickness scaling (down to 3 nm) induced mobility enhancement in UTB GeOI nMOSFETs

Abstract: Electron mobility of ultra thin body (UTB) GeOI «MOSFETs with body thickness (T body ) down to 3 nm has been systematically investigated and significant mobility enhancement with decreasing T body has been observed for the first time. This channel thickness scaling induced mobility enhancement can be attributed to the unique physical property of ultra thin Ge where the electron effective mass reduces with scaling T body through the band structure modification.

High electron mobility transistor (hemt) and process of forming the same

Abstract: A High Electron Mobility Transistor (HEMT) and a process of forming the same are disclosed. The HEMT includes a substrate, a channel layer, a barrier layer, and heavily doped regions made of metal oxide. The channel layer and the barrier layer provide recesses and a mesa therebetween. The heavily doped regions are formed by partially removing in a portion thereof on the mesa and have slant surfaces facing the gate electrode. The slant surfaces make angle of 135° to 160° against the top horizontal level of the mesa.

Determination of intrinsic mobility of a bilayer oxide thin-film transistor by pulsed I–V method

Abstract: Amorphous oxide semiconductor thin-film transistors (TFT) have been considered as outstanding switch devices owing to their high mobility. However, because of their amorphous channel material with a certain level of density of states, a fast transient charging effect in an oxide TFT occurs, leading to an underestimation of the mobility value. In this paper, the effects of the fast charging of high-performance bilayer oxide semiconductor TFTs on mobility are examined in order to determine an accurate mobility extraction method. In addition, an approach based on a pulse I D -V G measurement method is proposed to determine the intrinsic mobility value. Even with the short pulse I D -V G measurement, a certain level of fast transient charge trapping cannot be avoided as long as the charge-trap start time is shorter than the pulse rising time. Using a pulse-amplitude-dependent threshold voltage characterization method, we estimated a correction factor for the apparent mobility, thus allowing us to determine the intrinsic mobility.

Effects of Growth Conditions on the Measured Electrical Properties of Monolayer Molybdenum Disulfide

Abstract: : Molybdenum disulfide (MoS2) is a 2-D material that shows promise for flexible electronics, low-power applications, and optoelectronics due to its atomic thickness, high strain limit, large Ion/Ioff, and direct bandgap. We report on the electrical characterization of MoS2 transistors fabricated from US Army Research Laboratory-grown MoS2 and focus on how the MoS2 growth conditions affect the electrical performance. Metrics such as electron mobility, threshold voltage, hysteresis, and contact resistance are calculated for multiple devices on each growth condition. Measured devices had an electron mobility in the range of 115 cm2/Vs. MoS2 grown with lower sulfur precursor purity had the lowest mobility and a negatively shifted threshold voltage. A longer MoS2 growth time led to devices with the highest measured mobility. Transferring the MoS2 to a new substrate and modifying the growth setup to a 2-boat process show potential for improving device performance and prompt further investigation.

Strain-induced increase of electron mobility in ultra-thin InGaAs-OI MOS transistors

Abstract: The impact of strain on the electron mobility is investigated in ultra-thin InGaAs-OI channels by combining tight-binding bandstructure simulations, self-consistent Schrodinger-Poisson, and mobility simulations including all relevant scattering mechanisms. Our model shows that strain induced mobility improvement increases with body thickness downscaling, up to 164% in 4 nm-thick InGaAs channels in strong inversion.

Electron mobility in thin In0.53Ga0.47As channel.

Abstract: Channel thickness Tch dependence of electron mobility μκρρ in thin In0.53Ga0.47As channels was investigated at temperatures T from 35 to 300 K using conventional parametric and pulsed ID-measurements, including a novel technique with time resolution down to 10 ns. It is show that accurate mobility measurements can be obtained using low T and/or fast pulsed measurements, thus avoiding significant underestimations of μκρρ due to charge trapping with slow/parametric measurements. Furthermore, annealing is demonstrated to strongly suppress charge trapping, which results in μκρρ = 1015 cm²/Vs at Tch = 7.1 nm, carrier density Ns = 3 × 10¹² cm⁻², and T = 300 K. We demonstrate that room-temperature μκρρ degrades by less than 10% as Tch is scaled from 300 nm down to 7 nm, thus indicating that there is no “mobility bottleneck” down to Tch = 7 nm.

Quantum Confinement in High Electron Mobility Transistors

Abstract: Modulation-doped semiconductor nanostructures exhibit extraordinary electrical and optical properties that are quantum mechanical in nature. The heart of such structures lies in the heterojunction of two epitaxially grown semiconductors with different band gaps. Quantum confinement in this heterojunction is a phenomenon that leads to the quantization of the conduction and the valence band into discrete subbands. The spacing between these quantized bands is a very important parameter that has been perfected over the years into device applications. Most of these devices form lowdimensional charge carriers that potentially allow optical transitions between the subbands in such nanostructures. The transition energy differences between the quantized bands/levels typically lie in the infrared or the terahertz region of the electromagnetic spectrum and can be designed according to the application in demand. Thus, a proper understanding and a suitable external control of such intersubband transitions (ISTs) are not only important aspects of fundamental research but also a necessity for optoelectronic device applications specifically towards closing the terahertz gap.

Study of Electron Transport in Fullerene (C60) Quantum Confined Channel Layer Based Field Effect Transistor

Abstract: In this work, we modelled a simple n-channel Si Metal-Quantum confined layer-Semiconductor Field Effect Transistor (MQSFET), which resembles exactly as the conventional Si Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) where SiO2 dielectric layer is replaced with a wide band gap C60 quantum confined layer of thickness 3nm and gold (Ψ=5.1eV) as metal contact. The capacitance and voltage characteristics at different temperatures from 100 K to 500 K and energy band gap are studied using Multi-dielectric Energy Band Diagram Program (MEBDP) simulation software, performed current-voltage transistor characteristics and analyzed the mobility of the charge carrier in the MQS sandwiched device structure using the Caughey-Thomas high saturation mobility model and the Lombardi surface mobility model. In these studies, we inferred a very low threshold voltage, when the donor concentration in the p-Si substrate is tuned between 1E16 to 1E17 cm-3 and a saturated flow of nanoamperes range of charge carrier at a low gate potential is even possible.

A novel enhancement mode AlGaN/GaN high electron mobility transistor with split floating gates

Abstract: A novel enhancement-mode AlGaN/GaN high electron mobility transistor (HEMT) is proposed and studied. Specifically, several split floating gates (FGs) with negative charges are inserted to the conventional MIS structure. The simulation results revealed that the decreases with the increase of polarization sheet charge density and the tunnel dielectric (between FGs and AlGaN) thickness, while it increases with the increase of FGs sheet charge density and blocking dielectric (between FGs and control gate) thickness. In the case of the same gate length, the will left shift with decreasing FG length. More interestingly, the split FGs could significantly reduce the device failure probability in comparison with the single large area FG structure.

Characterization of asymmetric electron and hole transport in a high-mobility semiconducting polymer

Abstract: The electron and hole transport properties in a high-mobility n-type copolymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diy1]-alt-5,5′-(2,2′-dithiophene)}[P(NDI2OD-T2), PolyeraActivInk™ N2200] are investigated. The electron mobility is observed to be more than two orders of magnitude higher than the hole mobility. The thickness-dependent current density versus voltage (J–V) characteristics of N2200 electron-only and hole-only devices cannot be well described using the conventional mobility model. However, the thickness-dependent and temperature-dependent J–V characteristics of N2200 electron-only and hole-only devices can be accurately described using our recently introduced improved mobility model only with a single set of parameters. Within the improved model, the mobility depends on three important physical quantities: the temperature, carrier density, and electric field. For the semiconducting polymer studied, we find the width of the Gaussian density of states σ = 0.082 eV and the lattice constant a = 0.8 nm for electron transport, while the width of the Gaussian density of states σ = 0.11 eV and the lattice constant a = 0.8 nm for hole transport. It is clear that hole transport exhibits a significantly stronger disorder than electron transport. This is also reflected in the lower hole mobility, as compared to the electron mobility.

Phonon Controlled Temperature Dependence of Electron Mobility in 2DEG of GaAs Surface Layer

Abstract: The acoustic phonon limited zero-field mobility of free electrons is estimated in a degenerate two dimensional electron gas (2DEG) formed in semiconductor interface considering the effect of screening of the free carriers and the true phonon distribution which are indeed dominant characteristics of electron-phonon scattering at low lattice temperatures. Numerical calculations are made to observe the effect of screening on mobility values in GaAs surface layer and the result obtained here is compared with available experimental data and other theoretical result.