Papers by Keyword: Transistor

Abstract: Ethanol sensor has been widely used in our daily life and industrial production, such as drunk driving test, food fermentation monitoring, and industrial gas leakage monitoring. With the advent of the Internet of Things (IoT) era, ethanol sensors will develop towards miniaturization and low-power consumption in the near future. However, traditional ethanol sensors with large volumes and high-power consumption are difficult to meet these requirements. Therefore, it is urgent to study ethanol gas sensors based on new materials and new structures. Here, we demonstrated a flexible ethanol sensor based on an ion gel-coated graphene field-effect transistor (IGFET). The device has a small graphene channel size with a width of 300 μm and a length of 200 μm. The device showed a low operating voltage of less than |±1| V. When the device was put into an ethanol gas condition, the Dirac point voltage of the IGFET showed a negative shift, which means an n-type doping effect to the graphene channel. Furthermore, the sensor showed a normalized current change of-11% against an ethanol gas concentration of 78.51 g/L at a constant drain-source voltage of 0.1 V. In addition, the device exhibited a fast response time of ~10 s and a recovery time of ~18 s. Moreover, the detectable range of the device was found to as wide as 19.76-785.1 g/L. Based on the above results, the flexible IGFET-based ethanol sensor with small size and low-power consumption has great potential to be used in the industrial production of the IoT era.

Abstract: This paper reviews the state-of-the-art technologies of the normally-off GaN Gate Injection Transistor (GIT) and its applications such as inverter for motor drive and Power Factor Collection (PFC). Fundamental performances such as the current-collapse-free operation and the excellent switching performance are reviewed.

Abstract: Purely vertical 4H-SiC JFETs have been modeled by using three different approaches: the analytical model, the finite element model and the compact model. The results of the modeling have been compared with experimental results on a series of fabricated self-aligned devices with two different channel lengths (0.3 and 1.1μm) and various channel widths (1.5, 2, 2.5, 3, 4 and 5 μm). For all the considered models I-V and C-V characteristics could be satisfactorily simulated.

Abstract: The effect of neutron, electron and ion irradiation on electrical characteristics of unipolar 1700V SiC power devices (JBS diodes, JFETs and MESFETs) was investigated. DLTS investigation showed that above mentioned projectiles introduce similar deep acceptor levels (electron traps) in the SiC bandgap which compensate nitrogen shallow donors and cause majority carrier (electron) removal. The key degradation effect occurring in irradiated devices is the increase of the ON-state resistance which is caused by compensation of the low doped n-type epilayer and simultaneous lowering of electron mobility. In the case of SiC power switches (JFET, MOSFET), these effects are accompanied by the shift of the threshold voltage. Radiation defects introduced in SiC power devices is unstable and some defects anneal out already at operation temperatures (below 175°C). However, this does not have significant effect on device characteristics.

Abstract: Carboxyl-modified graphene materials in both oxide and reduced state were explored in parallel for the preparation of field-effect transistors (FET). They were solution gated by phosphate buffer solution (PBS) (pH 7.2). Their conductance were examined and compared with unmodified graphene transistors, firstly. Then, after single strand DNA molecules were immobilized on reduced and oxide graphene transistors, their conductance and compared. Here ssDNA molecules were amino-tagged at the terminal five. It was found that ambipolar characteristic was exhibited by reduced graphene transistors, even they were undergone carboxyl modification. And it was also discovered that there were opposite conductance variation with the increasing of ssDNA concentrations and bigger changes were obtained by reduced carboxyl-modified graphene transistors.

Abstract: With the development of electronic technology, the electronic threats faced by microwave semiconductor devices was increasingly serious.In order to study the electrostatic discharge damage mechanism of bipolar silicon transistors, this paper analyzed the basic physical characteristics of bipolar transistor in electrostatic discharge, such as kirk effect and current crowding effect. Through analysis the human body electrostatic discharge model, established the ESD electric injury model of bipolar silicon transistor. If we knew the production process parameter of devices, we can calculate the ESD damage threshold for designing bipolar silicon device and providing a theoretical basis of parameter optimization. Finally the common ESD damage criterion were analyzed from different angles.

Abstract: Drain-induced barrier lowering (DIBL) is crucial in many applications of silicon nanowire transistors. This paper determined the effect of the dimensions of nanowires on DIBL. The MuGFET simulation tool was used to investigate the characteristics of the transistors. The transfer characteristics of transistors with different dimensions were simulated. The results show that longer nanowires with smaller diameters and lower oxide thickness decrease DIBL and tend to possess the best transistor characteristics.

Abstract: To achieve graphene channel transistors which have high on/off drain current ratio and unipolar behavior of drain current – gate voltage (ID-VG) characteristics, we fabricated and characterized the top gated graphene channel transistors with n-type doped SiC source/drain regions. Graphene layer was formed on SiC by high temperature annealing in vacuum, and Al2O3 was used as a gate insulator. For the graphene channel transistor with heavily doped n-SiC source/drain regions (doping concentration ND=4.5x1019cm-3) and a 4~6ML graphene channel, ambipolar behavior was observed. On the other hand, when ND was reduced to 4.5x1018cm-3 and a thin graphene layer was used, the suppression of hole current in ID-VG curve was observed.

Abstract: We explore the effect of processing on graphene/metal ohmic contact resistance, the integration of high-κ dielectric seeds and overlayers on carrier transport in epitaxial graphene, and directly demonstrate the importance of buffer elimination at the graphene/SiC(0001) interface for high frequency applications. We present a robust method for forming high quality ohmic contacts to graphene, which improves the contact resistance by nearly 6000x compared to untreated metal/graphene interfaces. Optimal specific contact resistance for treated Ti/Au contacts is found to average -7 Ohm-cm². Additionally, we introduce a novel seeding technique for depositing dielectrics by ALD that utilizes direct deposition of high-κ seed layers and can lead to an increase in Hall mobility up to 70% from as-grown. Finally, we demonstrate that buffer elimination at the graphene/SiC(0001) results in excellent high frequency performance of graphene transistors with f_T > 130 GHz at 75 nm gate lengths.

Abstract: This paper demonstrates the reliability of SiC vertical trench junction field-effect transistors (VJFET). Measurements are shown which prove that the device’s intrinsic gate-source pn junction is immune to degradation associated with recombination-enhanced dislocation glide. And after subjecting VJFETs to 1,000 hours of high-temperature bias stress, no measured parameter deviated from datasheet specifications. These results reflect the maturity and reliability of SemiSouth’s SiC VJFET technology, as well as tight process control over device parameters that are critical to circuit design and long-term system operation.