Showing papers on "Field effect published in 2022"

Momentum relaxation effects in 2D-Xene field effect device structures

Abstract: We analyze the electric field driven topological field effect transition on 2D-xene materials with the addition of momentum relaxation effects, in order to account for dephasing processes. The topological field effect transition between the quantum spin Hall phase and the quantum valley Hall phase is analyzed in detail using the Keldysh non-equilibrium Green's function technique with the inclusion of momentum and phase relaxation, within the self-consistent Born approximation. Details of the transition with applied electric field are elucidated for the ON-OFF characteristics with emphasis on the transport properties along with the tomography of the current carrying edge states. We note that for moderate momentum relaxation, the current carrying quantum spin Hall edge states are still pristine and show moderate decay with propagation. To facilitate our analysis, we introduce two metrics in our calculations, the coherent transmission and the effective transmission. In elucidating the physics clearly, we show that the effective transmission, which is derived rigorously from the quantum mechanical current operator is indeed the right quantity to analyze topological stability against dephasing. Exploring further, we show that the insulating quantum valley Hall phase, as a result of dephasing carries band-tails which potentially activates parasitic OFF currents, thereby degrading the ON-OFF ratios. Our analysis sets the stage for realistic modeling of topological field effect devices for various applications, with the inclusion of scattering effects and analyzing their role in the optimization of the device performance.

Study of oxygen plasma treatment on solution-processed SnO x thin-film transistors

Abstract: In this study, the effect of oxygen plasma treatment (OPT) on the electrical performance of the SnO x thin film transistors (TFTs) were investigated. The SnO x thin films were fabricated by solution process and integrated into the TFTs as channels. According to the x-ray photoelectric spectroscopy analysis, the oxygen vacancies in the SnO x thin films are significantly reduced after OPT. The electrical performances of the SnO x TFTs treated with various plasma power and treatment time were systematically studied. Compared with untreated SnO x TFT, the one with OPT of 40 W for 90 s exhibits optimum electrical performance, including the variation of the current on/off ratio (I on/I off) from ∼103 to 107 and threshold voltage (V TH) from −10.78 to 3.97 V. Meanwhile, the operation mode of the SnO x TFTs is changed from depletion mode to enhancement mode. When the SnO x TFT is integrated with high-k Al2O3 dielectric, the TFT exhibits better electrical performance, including the V TH of 0.14 V, an I on/I off of 107, a field-effect mobility (µ FE) of 5.57 cm2 V−1 s−1, and a subthreshold swing of 570 mV dec−1. These results prove that the OPT process for SnO x TFTs is a facile and efficient method in the flat panel display industries.

Body doping dependence of field-effect mobility in both n- and p-channel 4H-SiC metal-oxide-semiconductor field-effect transistors with nitrided gate oxides

Abstract: Both n- and p-channel SiC MOSFETs, the gate oxides of which were annealed in NO, with various body doping concentrations were fabricated. Despite the large difference in bulk mobility between electrons (1020 cm2 V−1 s−1) and holes (95 cm2 V−1 s−1), the maximum field-effect mobility in heavily-doped (∼5 × 1017 cm−3) MOSFETs was 10.3 cm2 V−1 s−1 for the n-channel and 7.5 cm2 V−1 s−1 for the p-channel devices. The measurements using body bias revealed that the field-effect mobility in both n- and p-channel SiC MOSFETs is dominated by the effective normal field rather than the body doping.

Influence of Graphene Dispersion in P3HT-Based Thin Film Organic Field Effect Transistors

Abstract: P3HT has been an important candidate in the domain of organic field-effect transistors. The impact of instilling graphene in P3HT for enhanced mobility of the combined system to utilize the best of both need not occur. This work demonstrates the impact of graphene in P3HT (g-P3HT) based thin film OFET. There is a drop in mobility with a low concentration of graphene in P3HT until a sufficient amount of quantity is infused into the P3HT system, beyond which the mobility starts increasing. The lowest mobility in the presence of graphene has been found to be 2.24 x 10E-4 compared to 2.34 x 10E-4 of pristine P3HT.

Study on the Field-effect Carrier Transport of Epitaxial Graphene on SiC

Abstract: We have studied the field-effect carrier transport of graphene on 4H silicon carbide substrate. In order to extract the electrical parameters, the top-gated field effect transistor has been fabricated. By fitting the measured results with Kim’s model, the field effect carrier mobility (µ) and the metal/graphene contact resistance (Rc) and the residual carrier concentration (n0) are derived to be 3382cm2/Vs, 2250Ω▪µm and 2.18×1013cm-2, respectively. It is noted that the large contact resistance did not affect the high field effect carrier mobility of our device. The high carrier mobility suggests that the SiC epitaxial graphene may be quite suitable for the future high speed electronic applications.

High mobility achieved in InGaZnO TFT with vacuum-gap as insulating layer

Abstract: In this Letter, an amorphous In-Ga-Zn-O (InGaZnO) thin-film transistor (TFT) structure with a vacuum-gap as a dielectric layer is proposed and investigated. Field-effect conduction at the vacuum/InGaZnO interfaces exhibits extraordinary effective mobility ( μ) up to 65 ± 20 cm2 V−1 s−1, while the μ is only around 10 cm2 V−1 s−1 at the SiO2/InGaZnO interfaces with similar film processing conditions. Temperature-dependent transport is performed for deeper insight of the physical origin of the much higher μ at the vacuum/InGaZnO interface. We have found the density of states (DOS) of tail states is notably lower for the transport near the vacuum (8 × 1017 compared to 1.1 × 1019 cm−3 eV−1 at the SiO2/vacuum interface). These indicate that traditional dielectric materials like SiO2 have strong effects on the charge transport degradation in InGaZnO TFTs by introducing extra energetic disorders, and the intrinsic charge transport in InGaZnO is potentially approaching those in poly-silicon TFTs. Exploring a high-quality dielectric layer should be one effective way to further optimize the electrical performance in TFTs based on amorphous oxide semiconductors.

14‐2: Student Paper: Enhanced Electrical Characteristics of Low‐Temperature Processed In‐Ga‐Zn‐O Thin‐Film Transistors with Oxygen Scavenging Layer

Abstract: In this study, the oxygen scavenging layer (OSL) was introduced between channel and gate insulator to improve the electrical characteristics even at 200"C fabrication of amorphous indium-gallium- zinc oxide thin-film transistors (a-IGZO TFTs). The OSL is a layer introduced between the channel layer and the gate insulator layer, which is thinly deposited to absorb oxygen in the effective channel of a-IGZO with annealing process. MgOx was used to make the OSL. The a-IGZO TFTs with OSL, even if annealed at a low-temperature of 200°C, exhibit improved electrical characteristics and stability under positive bias temperature stress (PBTS) compared to those without OSL: field-effect mobility from 8.15 to 16.08 cm2/Vs, subthreshold swing from 0.45 to 0.42 V/decade, on/off current ratio from 3.19 × 108 to 9.53 × 109. A threshold voltage shift under PBTS at 50 °C for 10,000 sec was decreased from + 8.94 V to + 1.98 V. These improvements are attributed to Mg of OSL absorbing oxygen ions in the effective channel layer of a-IGZO.