Papers by Keyword: Field Effect Transistor

Abstract: Hysteresis response of epitaxially grown graphene nanoribbons devices on semi-insulating 4H-SiC in the armchair and zigzag directions is evaluated and studied. The influence of the orientation of fabrication and dimensions of graphene nanoribbons on the hysteresis effect reveals the metallic and semiconducting nature graphene nanoribbons. The hysteresis response of armchair based graphene nanoribbon side gate and top gated devices implies the influence of gate field electric strength and the contribution of surface traps, adsorbents, and initial defects on graphene as the primary sources of hysteresis. Additionally, passivation with AlO_x and top gate modulation decreased the hysteresis and improved the current-voltage characteristics.

Abstract: This study presents the possibility of control of nanofluidics in the bio-inspired nanosized ion channel using a field effect transistor (FET) structure. We analyzed effects from main dominant factors to control the ion flow in nanosized channel such as electro-osmosis, diffusion effect, Coulomb force between ions and pressure force. Additionally, we suggest a strategy to control the ion flow accurately at the specific position in the nanochannel by handling the viscosity, ion molecular density, pressure, gate and trans-cis voltages of FET structure.

Abstract: In this work, the impact of uniaxial strain on the current-voltage characteristics and the key performance metrics of armchair graphene nanoribbon (AGNR) field-effect transistors (FETs) are thoroughly studied by means of an analytical quasi-ballistic transport model that incorporates the effects of hydrogen passivation and third nearest-neighbor interactions. The model leads to compact expressions for the current-voltage characteristics of the device with only two fitting parameters and is verified by atomistic quantum simulations. The values of these parameters should be changed fromdevice to device. The obtained results reveal the tunable nature of the performance metrics of AGNRFETs with the application of tensile strain. Gate capacitance, cutoff frequency, on/off drain-current ratio, intrinsic delay and power-delay product under strain applied to the three distinct families ofAGNRs, are evaluated. This study can offer useful insight and guidance for strain engineering of GNR-based FETs.

Abstract: Due to the difficulty in the selective synthesis of semiconductor (s-) and metal (m-) single-walled carbon nanotubes (SWCNTs), we still need to explore the selective extraction technology of s-SWCNTs. Using Poly[9-(1-octylonoyl)-9H-carbazole-2,7-diyl] (PCz) extraction of s-SWCNTs has attracted extensive attention in recent years, because it can selective extraction of large-diameter s-SWCNTs with high purity. However, influence of the molecular weight of this polymer on the s-SWCNTs selective extraction properties remains unclear. In this study, we used PCz with different average molecular weights to study the ability of selective extraction s-SWCNTs from pristine arc discharge carbon nanotubes. Spectra studies indicate that compared to the PCz with lower molecular weight, the PCz with higher molecular weight has better selective extraction ability, and can help to obtain s-SWCNTs with higher purity (>99%) and high yield. FETs devices have been prepared by s-SWCNTs obtained via PCz with higher molecular weight exhibit higher on/off ratio, lower off current and lower subthreshold swing. This work offers a reference of the design and synthesis of PCz polymer that performs sufficient selective ability in extracting s-SWCNTs with promising applications.

Abstract: It was found that at room temperature the value of the photoinduced current of Schottky diodes based on heterostructures InP/GaInAs/Pd at a hydrogen concentration of 0.03% is reduced by two orders of magnitude compared to the value without hydrogen. The value of the photoinduced current depends on the thickness of the depleted region on the surface of the semiconductor. A small change in the charged layer of H⁺ can cause a significant change in the thickness of this region and as a result, a strong change in the photoinduced current. This effect on current is much stronger than the influence of hydrogen concentration or capacitance without optical activation. As a result, it becomes possible to create hydrogen and hydrogen-containing gas sensors with much better sensitivity at room temperature. The original design of a miniature H₂ sensor including an IR LED, a Schottky diode with a Pd contact, a Peltier cooler and a thermosensor is demonstrated.

Abstract: 3D Simulation was carried out and compared with fabricated ZnO NWFET. The device had the following electrical output characteristics: mobility value of 10.0 cm²/Vs at a drain voltage of 1.0 V, threshold voltage of 24 V, and subthreshold slope (SS) of 1500 mV/decade. The simulation showed that the device output results are influenced by two main issues: (i) contact resistance (R_con ≈ 11.3 MΩ) and (ii) interface state trapped charge number density (Q_IT = 3.79 x 10¹⁵ cm^-2). The Q_IT was derived from the Gaussian distribution that depends on two parameters added together. These parameters are: an acceptor-like exponential band tail function g_GA(E) and an acceptor-like Gaussian deep state function g_TA(E). By de-embedding the contact resistance, the simulation is able to improve the device by producing excellent field effect mobility of 126.9 cm²/Vs.

Abstract: ZnO NWFETs were fabricated with and without Al₂O₃ passivation. This was done by developing a new recipe for depositing the thin film of ZnO. By using a high donor concentration of 1.7 x 10¹⁸ cm^-3 for the thin film, contact resistance values were lowered (passivated device had R_con = 2.5 x 10⁴ Ω; unpassivated device had R_con = 3.0 x 10⁵ Ω). By depositing Zn first instead of O₂, steep subthreshold slopes were obtained. The passivated device had a subthreshold slope of 225 mV/decade and the unpassivated device had a slope of 125 mV/decade. Well-behaved electrical characteristics have been obtained and the passivated device shows field effect mobility of 10.9 cm²/Vs and the un-passivated device shows a value of 31.4 cm²/Vs. To verify the results, 3D simulation was also carried out which shows that the obtained values of sub-threshold slope translate into interface state number densities of-1.86 x 10¹³ cm^-2 for the unpassivated device and 3.35 x 10¹⁴ cm^-2 for the passivated device. The passivated device is suitable for biosensing applications.

Abstract: A highly sensitive low-doped ZnO nanowire field effect transistor (NWFET) biosensor has been fabricated and measured. The low doped biosensor with NWFET transducer was used to sense charge of the following substances: lysozyme (LYSO), phosphate buffered saline (PBS), bovine serum albumin (BSA). It achieved maximum sensitivity of -543.2 % for the PBS-LYSO protein and 13,069 % for the PBS-BSA protein. These results were achieved because the electrical measurement and characterisation was focused on the charge effect of the LYSO and BSA acting on the ZnO nanowire subthreshold region. The nano-fabrication process is stable and reproducible. The high sensitivity of the ZnO NWFET biosensor can be exploited for selective analyte detection by functionalizing the nanowire surface with antibodies and/or other biomolecular probe molecules.

Abstract: Gas sensitive metal/metal-oxide field effect transistors based on silicon carbide were used to study the sensor response to benzene (C₆H₆) at the low parts per billion (ppb) concentration range. A combination of iridium and tungsten trioxide was used to develop the sensing layer. High sensitivity to 10 ppb C₆H₆ was demonstrated during several repeated measurements at a constant temperature from 180 to 300 °C. The sensor performance were studied also as a function of the electrical operating point of the device, i.e., linear, onset of saturation, and saturation mode. Measurements performed in saturation mode gave a sensor response up to 52 % higher than those performed in linear mode.

Abstract: Epitaxial graphene grown on semiinsulating silicon carbide was used to fabricate side gate graphene transistors. The transconductance of the side gate transistors is comparable to top gate designs. The transconductance decreases with increasing gate width independently on the gate to channel distance in agreement with the transconductance reduction in top gate transistor configu¬rations with increasing channel length. The transconductance of the side gate transistors decreases with increasing channel width due to a decreased specific gate capacitance.