Metal-insulator Field-effect Transistors Research Articles

Breakdown mechanism in 1 kA/cm2 and 960 V E-mode β-Ga2O3 vertical transistors

A high current density of 1 kA/cm2 is experimentally realized in enhancement-mode Ga2O3 vertical power metal-insulator field-effect transistors with fin-shaped channels. Comparative analysis shows that the more than doubled current density over the prior art arises from a larger transistor channel width; on the other hand, a wider channel also leads to a more severe drain-induced barrier lowering therefore premature transistor breakdown at zero gate-source bias. The observation of a higher current density in a wider channel confirms that charge trapping in the gate dielectric limits the effective field-effect mobility in these transistor channels, which is about 2× smaller than the electron mobility in the Ga2O3 drift layer. The tradeoff between output-current density and breakdown voltage also depends on the trap density. With minimal trap states, the output current density should remain high while breakdown voltage increases with decreasing fin-channel width.

Growth kinetic and composition of the interfacial layer for RF sputtering Al2O3 layer on germanium

PurposeThe quality of GeOx–Ge interface and the equivalent oxide thickness (EOT) are the main issues in fabricating high-k/Ge gate stack due to the low-k of GeOx interfacial layer (IL). Therefore, a precise study of the formation of GeOx IL and its contribution to EOT is of utmost importance. In this study, the GeOx ILs were formed through post-oxidation annealing of sputtered Al2O3 on the Ge substrate. The purpose of this paper is to report on growth kinetics and composition of IL between Al2O3 and Ge for HCl- and HF-last Ge surface.Design/methodology/approachAfter wet chemical cleaning with HCl or HF, Al2O3 was grown onto the Ge surface by RF sputtering. Thickness and composition of IL formed after post-anneal deposition at 400°C in dry oxygen ambience were evaluated as a function of deposition time by FESEM and characterized by X-ray photoelectron spectroscopy, respectively.FindingsIt was observed that the composition and thickness of IL were dependent on the starting surface and an aluminum germinate-like composition was formed during RF sputtering for both HF- and HCl-last starting surface.Originality/valueThe novelty of this work is to investigate the starting surface of Ge to IL growth between Al2O3/Ge that will lead to the improvement in Ge metal insulator field effect transistors (MISFETs) application.

Flexible MISFET Devices From Transfer Printed Si Microwires and Spray Coating

This paper presents two types of metal insulator field effect transistors (MISFETs) devices fabricated from Si microwires through a new manufacturing route involving a combination of printing and microfabrication technologies. Si microwires, developed through standard photolithography and etching steps, are transferred from a silicon on insulator wafer onto polyimide using stamp-assisted transfer printing. The MISFETs are then obtained by spray coating the dielectric layer and metal contact layer. Spray coating has been introduced here for the first time for deposition of organic dielectric on transfer printed Si microwires. Two groups of the devices are fabricated, one based on a single Si microwire and the other based on the array of 15 microwires of similar dimensions. The variations in the output response of the two groups of devices has been investigated. The devices based on array of microwires are observed to have less variation in the output response, with lesser standard deviations as compared to MISFETs made from single Si microwires.

Monolithic integration of an AlGaN/GaN metal—insulator field-effect transistor with an ultra-low voltage-drop diode for self-protection

In this paper, we present a monolithic integration of a self-protected AlGaN/GaN metal—insulator field-effect transistor (MISFET). An integrated field-controlled diode on the drain side of the AlGaN/GaN MISFET features a self-protected function for a reverse bias. This diode takes advantage of the recessed-barrier enhancement-mode technique to realize an ultra-low voltage drop and a low turn-ON voltage. In the smart monolithic integration, this integrated diode can block a reverse bias (> 70 V/μm) and suppress the leakage current (< 5 × 10−11 A/mm). Compared with conventional monolithic integration, the numerical results show that the MISFET integrated with a field-controlled diode leads to a good performance for smart power integration. And the power loss is lower than 50% in conduction without forward current degeneration.

New method for selectivity enhancement of SiC field effect gas sensors for quantification of NO x

A silicon carbide based enhancement type metal insulator field effect transistor with porous gate metallization has been investigated as a total NOx sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle optimized for NOx detection and quantification in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted and evaluated with multivariate statistics (e.g. linear discriminant analysis) allowing quantification of NOx . Additional cleaning-cycles every 30 min improve the stability of the sensor further. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can be reduced effectively. Measurements have proven that different concentrations of NOx can be detected even in a changing mixture of other typical exhaust gases under dry and humid conditions. In addition to that, unknown concentrations of NOx can be detected based on a small set of training data. It can be concluded that the performance of GasFETs for NOx determination can be enhanced considerably with temperature cycling and appropriate signal processing.

Self-consistent electrothermal Monte Carlo simulation of single InAs nanowire channel metal-insulator field-effect transistors

Electron transport and self-heating effects are investigated in metal-insulator field-effect transistors with a single InAs nanowire channel, using a three-dimensional electrothermal Monte Carlo simulator based on finite-element meshing. The model, coupling an ensemble Monte Carlo simulation with the solution of the heat diffusion equation, is carefully calibrated with data from experimental work on these devices. This paper includes an electrothermal analysis of the device basic output characteristics as well the microscopic properties of transport, including current-voltage curves, heat generation and temperature distributions, and electron velocity profiles. Despite the low power dissipation, results predict significant peak temperatures, due to the high power density levels and the poor thermal management in these structures. The extent of device self-heating is shown to be strongly dependent on both device biasing configuration as well as geometry.

Design and Analysis of a 20 Gbps Metal-Insulator-Field Effect Transistor Photoreceiver for the OptoElectronic Integrated Circuit Receiver Applications

High-speed photoreceivers are important components for future high-bit rate communication systems. The use of a monolithical integration of photodetector and amplifier avoids loss making interconnections and enables high-speed performance, small size and cost-saving high frequency packaging. Particularly with respect to a commercial use, the degree of reproducibility and reliability has to be very high. The elimination of process uncertainties is indispensable. Hence, in our photoreceiver development, a photoreceiver based on optically gated metal-insulator-field effect transistor (MISFET) has been proposed to perform both the functions as photodetector and preamplifier. For future long-haul communication systems operate at bitrates of 40 Gbit/s and for broad-band mobile access systems using 38-GHz or 60-GHz carrier frequencies, ultrafast photoreceivers have to be provided. Therefore, an integration concept for InP-based optoelectronic monolithic integrated circuits for the 1.55-μm wavelength regime is studied, which allows independent optimization of the constituting devices. The device can be considered as a nano device as all the device parameters are in nanometer range. The design and characterization of a novel high sensitivity photo MISFET based OEIC receiver for using in 1.55 μm applications has been carried out based on 3D numerical modeling and device simulation. The bit error rate (BER) and sensitivity of the photoreceiver have also been computed. The proposed OEIC receiver has a transimpedance gain of 71.35 dB and sensitivity at 20 Gb/s for a BER of 10 -9 has been found to be -66 dBm. This seems to be a promising technology which will greatly simplify the design of optoelectronic integrated circuits including OEIC repeaters.

High Transconductance MISFET With a Single InAs Nanowire Channel

Metal-insulator field-effect transistors (FETs) are fabricated using a single n-InAs nanowire (NW) with a diameter of d = 50 nm as a channel and a silicon nitride gate dielectric. The gate length and dielectric scaling behavior is experimentally studied by means of dc output- and transfer-characteristics and is modeled using the long-channel MOSFET equations. The device properties are studied for an insulating layer thickness of 20-90 nm, while the gate length is varied from 1 to 5 mum. The InAs NW FETs exhibit an excellent saturation behavior and best breakdown voltage values of V BR > 3 V. The channel current divided by diameter d of an NW reaches 3 A/mm. A maximum normalized transconductance gm /d > 2 S/mm at room temperature is routinely measured for devices with a gate length of les 2 mum and a gate dielectric layer thickness of les 30 nm.

SiGe and Ge Cryogenic Power Transistors

We have undertaken development of power semiconductor devices based on SiGe and Ge, intended for operation over a wide temperature range, from room temperature down to deep cryogenic temperatures, ~30 K (~ -240{degree sign}C). We summarize results for Ge diodes (~10 A/400 V), Ge junction field-effect transistors (Ge JFETs, ~0.5 A/30 V), Ge metal-insulator field-effect transistors (Ge MIS-FETs ~1 A/20 V) and SiGe heterojunction bipolar transistors (SiGe HBTs, ~10 A/50 V). As a practical demonstration, we have used SiGe HBTs and SiGe diodes as the active devices in 100-W power-conversion circuits, operating from room temperature down to ~30 K (~ -240{degree sign}C) with increased efficiency as temperature de-creases. Our developments demonstrate the potential of alternative semiconductor materials to provide excellent performance for power applications down to deep cryogenic temperatures.

Use of amorphous carbon as a gate insulator for GaAs and related compounds

Deposition of gate insulator in the arsenic-based compound semiconductors (such as GaAs, AlGaAs), always causes stoichiometric changes in these materials. The deposition of any materials above 350 °C results in the segregation of As at the surface of the semiconductor, which deteriorates the metal–insulator field effect transistor properties. a-C:H can be deposited at room temperature and hence the effect of temperature on arsenic segregation can be eliminated. This work investigates the use of a-C:H as a gate insulator in arsenic-based compound semiconductors.

GaAs metal insulator field effect transistors with excellent intrinsic transconductance and stable drain currents using (NH/sub 4/)/sub 2/Sx chemical treatment

Metal insulator semiconductor field effect transistors (MISFETs) and MIS capacitors are fabricated using Al metal-gate and PECVD silicon nitride (Si/sub 3/N/sub 4/) gate-insulator on commercial GaAs epitaxial wafers after treating the channel regions with (NH/sub 4/)/sub 2/S/sub x/. It is shown that the post metallization annealing (PMA) of these devices improves the transconductance and reduces the interface state density (D/sub it/) considerably. This is attributed to the additional passivation effect of hydrogen diffusing to the interface from the Si/sub 3/N/sub 4/ during the PMA. An intrinsic transconductance of 30.7 mS/mm which is 75% of the theoretical maximum limit of 40.5 mS/mm has been achieved using silicon nitride gate insulator thickness of 1100 /spl Aring/. Stability of the drain currents in these devices is demonstrated to be excellent.

Thin film diamond metal-insulator field effect transistor for high temperature applications

bstract A high temperature depletion-mode metal-insulator field effect transistor (MISFET) has been fabricated from thin film polycrystalline diamond with a p-type (boron doped) channel and an insulating diamond gate. This device was successfully operated at 300 °C with low gate leakage currents, displaying pinch-off when in depletion and high levels of channel current modulation in enhancement. A transconductance value of 174 μS mm −1 has been measured, the highest reported value to date for this type of device.

GaN-AlxGa1−xN Heterostructures Deposition by Low Pressure Metalorganic Chemical Vapor Deposition for Metal Insulator Semiconductor Field Effect Transistor (Misfet) Devices

ABSTRACTIn this paper we report the fabrication and characterization of a metal insulator semiconductor field effect transistor (MISFET) based on single crystal GaN-AlxGa1−xN heterostructures. The device structure layers were deposited over sapphire substrate using low pressure metalorganic chemical vapor deposition. We discuss the fabrication and characterization of MISFET devices using single crystal GaN as the insulator layer. These were fabricated on isolated mesas using TiAu for the source and drain ohmic contacts and silver for the gate Schottky. For devices with a gate length of 4 μm (channel opening i.e. source to drain separation of 10 μm), a transconductance of 20 mS/mm was obtained at -1 volt gate bias. Complete pinchoff was observed for a gate potential of -15 volts. Device performance is compared to that for a GaN MESFET of identical dimensions.Due to its direct bandgap tunable from 3.4 to 6.2 eV AlxGa1−xN is an important semiconductor for devices in the ultraviolet and visible parts of the spectrum. The large bandgap, potential of heterojunction formation and the insulating nature of AlN make AlxGa1−xN an ideal material system for high performance metal semiconductor field effect transistor (MESFET) devices requiring high operation temperatures. Availability of the insulator (single crystal AlN or GaN) also makes possible the fabrication of metal insulator field effect transistor (MISFET) devices which has been an elusive goal for the GaAs based III-V materials technology.High quality single crystal GaN films have been deposited on sapphire and several other semiconductor substrates using metalorganic chemical vapor deposition (MOCVD)1,2, molecular beam epitaxy (MBE)3 and vapor phase epitaxy (VPE)4. Recently we have reported on quantum confinement5, room temperature stimulated emission6, and 2-dimensional electron gas in GaN-AlxGa1−xN heterostructures7,8. We have also deposited single crystal insulating GaN and A1N over sapphire using atomic layer epitaxy9,10 and fabricated high responsivity photoconductors11. We now report on the fabrication and characterization of FET devices using single crystal GaN-AlxGa1−xN heterostructures. This forms the basis of high temperature transistor devices based on the AlxGa1−xN material system.

Reduced lattice temperature high-speed operation of pseudomorphic InGaAs/GaAs field-effect transistors

This letter presents a detailed study of the temperature dependence of submicron pseudomorphic InGaAs on GaAs substrate modulation doped field-effect transistors (MODFETs), doped-channel metal insulator field effect transistors (MISFETs), and metal semiconductor field-effect transistors (MESFETs). We determine similar variation in the measured extrinsic current gain cutoff frequency, FT, and similar dependencies of the effective electron velocity, veff, with reduced lattice temperature for the different field-effect transistors. The veff∼T−b where 0.15&amp;lt;b&amp;lt;0.20 over the temperature range of 300 to 110 K. These results provide direct experimental evidence that the saturated velocity of electrons is the most important parameter for high-speed operation and with proper design these different pseudomorphic InGaAs/GaAs field-effect transistors provide similar potential for high-speed operation.

Electrical properties and applications of InxAl1−xAs/InP

Prototype depletion mode heterojunction-insulated gate field-effect transistors using In0.43Al0.57As as a quasigate insulator were fabricated and their low-frequency properties were evaluated. Typical extrinsic transconductances of gm=20 mS/mm were obtained for devices with gate length of 6 μm which exhibited no direct current drain current instabilities. A qualitative fit to a metal–insulator field-effect transistor (MISFET) model was obtained using the material parameters of the InP and In0.43Al0.57As epilayers and assuming that this quasi-insulator could be represented as a conventional insulator. The equilibrium surface potential has been determined to be −0.05 eV. Capacitance–voltage (C–V) and conductance-frequency measurements made on similar heterojunction capacitors show that the maximum interface state density is in the low 1011/cm2 eV range and confirm the slight depletion of the InP surface.

Current drift mechanism in In0.53Ga0.47As depletion mode metal-insulator field-effect transistors

A study of current drift phenomena of InGaAs depletion mode metal-insulator field-effect transistors fabricated with plasma enhanced chemical vapor deposited Si3N4 is reported for the first time. The data indicate that the current varies logarithmically versus time and that the capture mechanism does not depend on temperature. A strong correlation is demonstrated between the amplitude of the hysteresis of C(V) curves measured on metal-insulator-semiconductor devices and the total oxide thickness located between the deposited dielectric film and the InGaAs layer. This behavior suggests that states situated in this native oxide layer are responsible for the current drift. Moreover, these states are energetically distributed in the band gap of InGaAs.