Fabrication and characterization of the amorphous-silicon staticinduction transistor

Experimental results for the fabrication and electrical characterization of a hydrogenated amorphous silicon static induction transistor are reported. The I-V measurements demonstrate the triode-like enhancement mode operation of the device and show an on-off current ratio of 300 and a pinchoff voltage of -9.5 V for V_ds=6 V. Numerical simulation suggests that the differences between experimental and theoretically predicted results are due to the presence of a high-density-of-states layer at the a-Si:H/a-Si:H interface     

Modeling the turn-off characteristics of the bipolar-MOS transistor

Since the turn-off speed of the new bipolar-MOS power transistor is slow compared to that of a MOSFET, it is important to understand the limiting mechanism and the prospect for future improvement. In this letter, it is demonstrated that the turnoff waveform can be explained by a model based on a simple equivalent circuit and the transistor open-base turn-off process. The model is applied to explore the impact of some process modifications on speed improvement and to study the tradeoff between speed and on-resistance.     

槽栅MOSHEMT研制与特性分析

An A1GaN/GaN recessed-gate MOSHEMT was fabricated on a sapphire substrate. The device, which has a gate length of 1μm and a source-drain distance of 4μm, exhibits a maximum drain current density of 684mA/mrn at Vgs = 4V with an extrinsic transconductance of 219 mS/mm. This is 24.3% higher than the transconductance of conventional A1GaN/GaN HEMTs. The cut-off frequency and the maximum frequency of oscillation are 9.2 GHz and 14.1 GHz, respectively. Furthermore, the gate leakage current is two orders of magnitude lower than for the conventional Schottky contact device.     

Development and characteristics analysis of recessed-gate MOS HEMT

An AlGaN/GaN recessed-gate MOSHEMT was fabricated on a sapphire substrate. The device, which has a gate length of 1 μm and a source-drain distance of 4 μm, exhibits a maximum drain current density of 684 mA/mm at Vgs = 4 V with an extrinsic transconductance of 219 mS/mm. This is 24.3% higher than the transconductance of conventional AlGaN/GaN HEMTs. The cut-off frequency and the maximum frequency of oscillation are 9.2 GHz and 14.1 GHz, respectively. Furthermore, the gate leakage current is two orders of magnitude lower than for the conventional Schottky contact device.     

Power and linearity characteristics of field-plated recessed-gate AlGaN-GaN HEMTs

Record power density and high-efficiency operation with AlGaN-GaN high-electron mobility transistor (HEMT) devices have been achieved by adopting a field-plated gate-recessed structure. Devices grown on SiC substrate yielded very high power density (18.8 W/mm with 43% power-added efficiency (PAE) as well as high efficiency (74% with 6 W/mm) under single-tone continuous-wave testing at 4 GHz. Devices also showed excellent linearity characteristics when measured under two-tone continuous-wave signals at 4 GHz. When biased in deep-class AB (33 mA/mm, 3% I/sub max/) device maintained a carrier to third-order intermodulation ratio of 30 dBc up to a power level of 2.4 W/mm with 53% PAE; increasing bias current to 66 mA/mm (6% I/sub max/) allowed high linear operation (45 dBc) up to a power level of 1.4 W/mm with 38% PAE.     

Modeling of Schottky coupled transistor logic

The SCTL gate which promises increased speed and reduced power is discussed. It involves the use of a single lowly doped collector incorporating Schottky diodes to decode the output. A complete electrical model is formulated and compared with experimental results. The model is then used to optimize this structure with respect to extrinsic and intrinsic base doping and collector doping, and it resulted in an 8.5 ns fanout four device on a 2.5 /spl mu/m epilayer. Finally, the model is used to study the possibility of Schottky clamping the base collector, and it was found that higher collector doping was needed for a minimum delay.     

On the field-effect transistor characteristics

A theoretical analysis demonstrates that the relationship between IDand VDSfor one value of VGSis sufficient to completely describe the device behavior for any channel impurity profile. A simple graphical procedure is given to generate a complete set of characteristics from the results at one value of VGS. Measurements on ann-channel FET are given to support the theoretical conclusion and to demonstrate the graphical technique.     

Modeling base crowding in a bipolar transistor

It is shown that in a model of a bipolar transistor with a rectangular configuration, the base-crowding effect may be represented by a diode and a resistor in parallel between the internal base point and the external base connection with an accuracy of better than four percent.     

Modeling of the electrical characteristics of an organic field effect transistor in presence of the bending effects

An analytical model incorporating the density of trap states for a bendable organic field effect transistor (OFET) is presented in this paper. The aim of this work is to propose a novel modeling framework to quantitatively characterize the bending effects on the electrical properties of an OFET in the linear and saturation regimes. In this model, the exponentially distributed shallow trap states are introduced into the Poisson equation to describe the carrier transports in the channel. The carrier mobility takes into account the low field mobility enhancement under gradual channel approximation and high field degradation. As a result, the generalized current-voltage transistor equations are derived for the first time to reflect the transconductance relationships of the OFET with trap states. In addition, an electro-mechanical coupling relationship is established per the metaphorical analogy between inorganic and organic semiconductor energy band models to quantify the stress-induced variations of the carrier mobility, and the threshold voltage. It is revealed that the before- and after-bending transconductances, predicted from the derived analytical model, are in good agreement with the experimental data measured from DNTT-based OFET bending tests.     

A new self-aligned recessed-gate InP MESFET

We describe a new self-aligned recessed-gate InP MESFET. In this structure, material selective and anisotropic etching properties of InP/InGaAsP system are utilized to alleviate the difficulties associated with channel recess and gate alignment. Using this technique a 1-µm Al-gate InP MESFET with a transconductance ∼ 110 mS/mm is demonstrated.     

Current modulation characteristics in optically-controlledfield-effect transistor

A new type optically-controlled field-effect transistor was demonstrated. This device was composed of GaAs material system for the FET region and GaInAs/InP material system for the absorption region, and these regions were electrically isolated by polyimide and SiO₂. When 1.55 μm wavelength light entered the absorption region, about 120 μA of source-to-drain current was modulated due to the field-screening effect     

Modeling of threshold voltage of a quadruple gate transistor

In this paper, a three dimensional analytical solution of electrostatic potential is presented for undoped (or lightly doped) quadruple gate MOSFET by solving 3-D Poisson's equation. It is shown that the threshold voltage predicted by the analytical solution is in close agreement with TCAD 3-D numerical simulation results. For numerical simulation, self-consistent Schrodinger-Poisson equations, calibrated by 2D non equilibrium green function simulation, are used. This analytical model not only provides useful physics insight of effects of gate length and body width on the threshold voltage, but also serves as a basis for compact modeling of quadruple gate MOSFETs.     

Analysis of insulated gate transistor turn-off characteristics

A model based upon a MOSFET driving a wide-base p-n-p transistor is presented for analysis of the turn-off behavior of n-channel insulated gate transistors. This model is found to provide a very good quantitative explanation of the shape of the collector current waveform during turn-off. Verification was accomplished using insulated gate transistors (IGT's) fabricated with two voltage ratings and a variety of radiation doses. This analysis allows the separation of the channel (electron) and minority carrier (hole) current flow in the IGT for the first time.     

Current-voltage characteristics of a silicon nanowire transistor

The nanowires and nanotubes are being considered as the best candidates for high-speed applications. It is shown that the high mobility does not always lead to higher carrier velocity. The ultimate drift velocity due to the high-electric-field streaming are based on the asymmetrical distribution function that converts randomness in zero-field to streamlined one in a very high electric field. The limited drift velocity is found to be appropriate thermal velocity for a nondegenerately doped sample of silicon, increasing with the temperature, but independent of carrier concentration. However, the limited drift velocity is the Fermi velocity for a degenerately doped silicon nanowire, increasing with carrier concentration but independent of temperature. The results obtained are applied to the modeling of the current-voltage characteristics of a nanowire transistor.     

Temperature behavior of insulated gate transistor characteristics

The Insulated Gate Transistor (IGT) is a new power semiconductor device with the high input impedance features of the power MOSFET and the ability to operate at high current densities even exceeding that of power bipolar transistors. The high temperature operating characteristics of the device are discussed here. Unlike the power MOSFET whose operating current density decreases by over a factor of 2 when the ambient temperature is raised to 150°C, the IGT is found to maintain its high operating current density at elevated temperatures. The temperature coefficient of the output current is found to be positive at forward drops below 1.5 V and negative at forward drops above 1.5 V. These characteristics make the IGT suitable for applications with high ambient temperatures. The results also indicate that these devices can be paralleled without current hogging problems if the forward conduction occurs at forward voltage drops in excess of 1.5 V.     

Modeling of ionizing irradiation influence on Schottky-gate field-effect transistor

Mechanism of radiation effects in semiconductor (GaAs) is described. Analytic and numerical (equivalent circuit and quasi-hydrodynamic methods) models of ionizing irradiation influence on semiconductor devices are discussed. The GaAs microwave MESFET was selected as the investigation object. The combination of the quasi-hydrodynamic and equivalent circuits methods should provide a possibility to take into account all essential effects and at the same time to save the computation time in comparison with Monte Carlo method.