GaAs Metal Semiconductor Field Effect Research Articles

Effect of temperature on (TV) statics characteristics of GaAs Mesfet

The GaAs metal semiconductor field effect transistors called mesfets are the most active components used in microwave applications. To better exploit the performance of these components circuits, it is necessary to develop techniques for sophisticated numerical computation based on physical mechanisms that govern the operation of these devices. The static properties of GaAs MESFET could be determined from an original analytical study based on the resolution of the semiconductor fundamental equations. Then we will study the equation of thermal resistance as a function of the physical parameters of MESFETs by analogy electric thermal resistance RTH will be determined as the ratio of the difference of temperature on the thermal dissipation. The model took into account the difference between the temperature of the component and the ambient temperature and the effect of temperature on the parameters of the component.

Analytical modelling of the current ( I )–voltage ( V ) characteristics of sub‐micron gate‐length ion‐implanted GaAs MESFETs under dark and illuminated conditions

An analytical model for current (I)–voltage (V) characteristics of a short-channel ion-implanted GaAs MESFET has been presented for dark and illuminated conditions. For the sake of simplicity, the non-analytic (i.e. non-integral) Gaussian doping function commonly considered for the channel doping of an ion-implanted GaAs metal semiconductor field effect transistor (MESFET) has been replaced by an analytic Gaussian-like doping profile in the vertical direction. The device uses an indium–tin oxide-based Schottky gate through which an optical radiation of 0.87 μm wavelength is coupled from an external source into the device to modulate the I–V characteristics of the short-gate length GaAs MESFET. The coupled light generates electron–hole pairs in the active channel region below the gate and develops a photovoltage across the Schottky gate–channel junction and modulates the device characteristics. This study also includes the modelling of this photovoltaic effect by taking the short-gate length effects into consideration. The developed model includes the effects of doping profile and device parameters on the drain current of the short-channel ion-implanted GaAs MESFETs under dark and illuminated conditions of operations. The accuracy of the proposed model is extensively verified by comparing the theoretically predicted results with numerical simulation data obtained by using the commercially available ATLASTM device simulation software.

Current oscillations and low-frequency noises in GaAs MESFET channels with sidegating bias

Low-frequency noises (LFN) and noise-like oscillations (NLO) in GaAs metal semiconductor field effect transistor (MESFET) channel current were investigated under sidegating bias conditions. It was found that the fluctuations of the channel current were directly dependent upon the sidegating bias. As the sidegating bias decreased, the amplitudes of the oscillations would increase correspondingly. Furthermore, the LFN and NLO would attenuate sharply when the sidegating bias increased to more than a certain voltage. Two mechanisms are presented to demonstrate that the effective substrate resistivity or the channel-substrate junction modulated by sidegating bias and deep level traps would take responsibilities for the LFN and NLO.

Electron Transport Behavior on Gate Length Scaling in Sub-50-nm GaAs Metal Semiconductor Field Effect Transistors

Short channel GaAs Metal Semiconductor Field Effect Transistors (MESFETs) have been fabricated with gate length to 20 nm, in order to examine the characteristics of sub‐50 nm MESFET scaling. Here the rise in the measured transconductance is mainly attributed to electron velocity overshoot. For gate lengths below 40 nm, however, the transconductance drops suddenly. The behavior of velocity overshoot and its degradation is investigated and simulated by using a transport model based on the retarded Langevin equation (RLE). This indicates the existence of a minimum acceleration length needed for the carriers to reach the overshoot velocity. The argument shows that the source resistance must be included as an internal element, or appropriate boundary condition, of relative importance in any model where the gate length is comparable to the inelastic mean free path of the carriers.

An Improved Model for GaAs MESFETs Suitable for a Wide Bias Range

In this letter, we present a new large signal model for GaAs metal-semiconductor field effect transistors, incorporating features for enhancing the bias range for which accuracy is maintained, for use in the simulation of microwave circuits. The model parameters for a specific case were extracted from a wide range of dc I-V and S-parameter data, and the simulated behavior was observed to match the measured data closely. The model includes the possibility of showing negative slopes of the I-V curves at high power without sacrificing accuracy in predicting radio frequency behavior, while remaining simple enough for use in simulation tools

Analysis of DC Characteristics and Small Signal Equivalent Circuit Parameters of GaAs Metal–Semiconductor Field Effect Transistors with Different Gate Lengths and Different Gate Contours by Two-Dimensional Device Simulations

The gate length and gate contour of a GaAs metal–semiconductor field effect transistor (MESFET) device play important roles in determining the small signal circuit parameters and large signal breakdown voltage behavior. GaAs MESFETs with different gate lengths and gate contours were studied by the two-dimensional (2-D) semiconductor device simulations to investigate the dependence of small signal circuit parameters and breakdown voltage on gate length and gate contour. The results show that gate length affects small-signal circuit parameter Cgs while gate contour affects Cgd. The breakdown voltage has strong dependence on gate contour and little dependence on gate length.

Noise Analysis of GaAs-MESFETs by Physics-Based Circuit Simulator Employing Monte Carlo Technique

SUMMARY Noise characteristics of GaAs metal-semiconductor field effect transistors (GaAs-MESFETs) with scaled-down dimensions are analyzed and modeled using a physics-based circuit simulator employing the Monte Carlo (MC) particle technique. The microscopic dynamics of electrons is also analyzed to investigate the mechanism of noise generation in a channel. Noise spectral densities of GaAs-MESFETs with two different geometries are estimated by evaluating fluctuations in instantaneous terminal currents. Then, minimum noise figures, Fmin, and noise figure circles are estimated using the noise spectral densities and Y-parameters. Because of an increase in y21 and suppression of an increase of noise spectral density, the device with an n+-region extending to below the drain-side edge of the gate contact exhibits a smaller noise figure. Suppression of the electron velocity fluctuation caused by electron transitions to higher valleys in a high electric field region is responsible for the noise suppression.

An improved method to estimate intrinsic small signal parameters of a gaas mesfet from measured dc characteristics

This investigation offers a technique to predict the ac behavior of mm wavelength GaAs metal semiconductor field effect transistors by using dc characteristics. To predict the intrinsic equivalent circuit parameters of the device from dc data, the measured dc characteristics are first simulated by employing a nonlinear dc model. The effects of biasing on the device ac parameters are evaluated for its low-noise applications. An improvement greater than 10% in predicting the ac response of the device is observed. The concept of depletion layer modification caused by the transverse electric field inside the channel is introduced for accurate Miller's capacitor modeling. It is assumed that with increased device biasing there are more unbalanced positive charges in the gate depletion toward the drain-side of the Schottky barrier. The electric field lines originated by these uncompensated charges induce an opposite charge density in the gate electrode. This modifies the gate biasing and hence the Schottky barrier depletion. As a result, the values of intrinsic ac device parameters change. It is observed that an accurate dc modeling is key to predicting an accurate ac small signal equivalent circuit of a device.

Improved performance of GaAs MESFETs through sulfidation of Pt/GaAs interface

Sulfidation was employed to decrease defective interfacial states of Pt/GaAs Schottky contacts. With nondestructive analysis using synchrotron radiation photoemission spectroscopy, it was found that the sulfur passivation of GaAs surface prior to Pt metallization effectively reduces interfacial elemental As and As-oxides. A reduced reverse leakage current as well as enhanced barrier height was confirmed from measurements of Schottky properties. These processes were introduced to a gate junction to improve gate leakage current characteristics and pinch-off properties of GaAs metal-semiconductor field effect transistors. The leakage current was decreased by several times and the threshold voltage was lowered by the sulfidation. The results indicate that the improved device properties after the sulfidation originate in the suppression of donor-type defect like excess As at the interface. On the basis of interfacial bonding characteristics, the electrical properties could be well understood.

Simple technique to determine the drain temperature in GaAs metal semiconductor field effect transistor

The effects of the operating temperature T and the drain voltage on the drain temperature in GaAs metal semiconductor field effect transistor (MESFET) are a serious problem, which do not receive enough attention in the scientific literature in the last years. This article presents a simple technique to determine the drain temperature by setting the equality between the field-dependent diffusivity-to-mobility ratio (nonlinear relation) and the constant ratio linear modeling. So, we investigate the impact of the high-field electron diffusivity model in GaAs on the characteristics of MESFETs. Two dimensional numerical simulation is used to describe significant physics in the characteristics for 0.5 μm MESFET GaAs.

The Effect of Oxygen Plasma on Activation Efficiency of Implanted Silicon in Gallium Arsenide

The effect of oxygen (O2) plasma on the threshold voltage (Vth) shift in gallium arsenide (GaAs) metal semiconductor field effect transistors (MESFETs), which were fabricated using ion implantation, was investigated. An O2 plasma process in barrel type reactor was found to cause a large Vth difference in MESFETs between wafers that were processed in the same batch. Numerical calculations were performed to understand the phenomena quantitatively. Experimental analyses, using secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS) and capacitance–voltage (C–V) measurement, were employed to confirm the key factor in the Vth shift mechanism. As a result, it was demonstrated that the shift was caused not by the etching of the FET channel but by the degradation of the activation efficiency. The degradation was related to the excessive oxidation, which proceeded by pulling up the substrate atoms and increased vacancy type defects in the channel.

Novel GaAs Metal–Semiconductor Field-Effect Transistors with InGaP/GaAs Multiple Quantum Barrier Capping and Buffer Layers

We present a novel GaAs metal–semiconductor field-effect transistor (MESFET) with InGaP/GaAs multiple quantum barrier (MQB) capping and buffer layers. The MQB structure with (29; 6, 5, 7; 8, 8, 1; 6, 5, 7; 29) periodic stacks was designed to increase effective-potential-barrier height. We demonstrate that, by using the InGaP/GaAs MQB capping layer, the gate Schottky barrier performance and gate leakage current are improved.

Influence of PECVD deuterated SiN x on GaAs MESFETs and GaAs/AlGaAs HBTs

The degradation of electrical characteristics of GaAs metal semiconductor field effect transistors (MESFETs) and heterojunction bipolar transistors (HBTs) can occur during plasma enhanced chemical vapor deposition (PECVD) of SiN X passivation films through the hydrogen passivation of dopants or creation of deep traps by ion bombardment or preferential loss of As. In this paper we report in the dc characteristics of MESFETs and HBTs deposited with SiN X using deuterated precursors (SiD 4/ND 3). For the MESFETs, changes in I DS, g m and channel sheet resistance were typically 25%, with process pressure being the most important parameter. For the HBTs, changes in β and sheet resistance of the base and emitter layers were again typically 15% for the conditions we investigated.

Effects of High Energy Proton Irradiation on DC Performance of GaAs Metal-Semiconductor Field Effect Transistors

GaAs metal-semiconductor field effect transistors were exposed to 40 MeV protons at fluences up to The extrinsic transconductance decreased from 98 to over this fluence range, with the drain-source current decreasing by under the same conditions. Based on the increases observed in the reverse breakdown voltage and the channel resistance, the main degradation mechanism appears to be introduction of deep electron traps which reduce the effective doping in the channel. The device threshold voltage and diode ideality factor showed little change upon irradiation. © 2002 The Electrochemical Society. All rights reserved.

Optical radiation and temperature-dependent microwave performance of optically biased GaAs metal-semiconductor field effect transistor

A physics-based analytical model for an optically biased GaAs metal-semiconductor field effect transistor, suitable for simulating optoelectronic integrated circuits, is presented. The main objective of the model is to show the effect of optical radiation and temperature on important parameters such as the bandgap energy, mobility, and carrier lifetime. It is found that optical radiation has negligible effect on these parameters, but the temperature affects them significantly. The effect of different scattering mechanisms on the drain-source current is also studied. Using this analysis, the model extends to describe optical radiation and temperature-dependent device characteristics such as the threshold voltage, transconductance, cutoff frequency, transit time, and responsiv- ity. Under illumination, a significant enhancement in device transconductance leading to an increase in cutoff frequency is observed.

Comparison of the effects of H 2 and D 2 plasma exposure on GaAs MESFETs

The effect of H 2 and D 2 plasma exposure on the dc and rf performance of implanted GaAs metal semiconductor field effect transistors (MESFETs) was examined as a function of the plasma parameters. This process simulates a worst-case scenario during the initial stages of dielectric passivation deposition onto the MESFET. The fact that the active channel is so close to the surface makes the MESFET extremely sensitive to effects such as hydrogen passivation, creation of midgap trap states or formation of donor-like surface states through loss of As. A wide variety of both dc (gate current, drain–source current, channel sheet resistances, threshold voltage, reverse breakdown voltage, transconductance and gate ideality factor) and rf ( f T, f MAX, gate–source resistance, drain–source resistance, drain and source resistance, intrinsic transconductance, gate–source, gate–drain, and drain–source capacitance and gate–source resistance) parameters were measured as a function of changes in ion energy and flux in the plasma.

Pressure dependence of Cu, Ag, andFe/n−GaAsSchottky barrier heights

The Schottky barrier height of intimate Cu/GaAs (110), Ag/GaAs (110), and Fe/GaAs (100) has been measured as a function of hydrostatic pressure. The pressure dependence of the Cu and $\mathrm{Ag}/n\ensuremath{-}\mathrm{GaAs}$ barrier heights of $97\ifmmode\pm\else\textpm\fi{}4\mathrm{m}\mathrm{e}\mathrm{V}/\mathrm{G}\mathrm{P}\mathrm{a}$ fall within the uncertainty of the pressure dependence of the ${\mathrm{As}}_{\mathrm{Ga}}$ defect and track the predicted value of ${\mathrm{As}}_{\mathrm{Ga}}$-rich interfaces. In contrast, the pressure dependence of the $\mathrm{Fe}/n\ensuremath{-}\mathrm{GaAs}(100)$ Schottky barrier height of $109\ifmmode\pm\else\textpm\fi{}7\mathrm{m}\mathrm{e}\mathrm{V}/\mathrm{G}\mathrm{P}\mathrm{a}$ does not fall within experimental error of these values and falls at nearly the predicted dependence of defect-free interfaces.

Analysis of buried gate MESFET under dark and illumination

D.C. analysis has been carried out for a buried-gate GaAs metal semiconductor field effect transistor (MESFET) under dark and front illumination. The photovoltage I-V characteristics and the transconductance of the device have been evaluated. The results indicate very good performance of the device compared to other devices like MESFET under back illumination and MESFET with front illumination having surface gate. Thus, buried-gate optical field effect transistor (OPFET) will be highly suitable for optical communication and optical computing.

Anisotropic Etching of Si and WSiN Using ECR Plasma of SF6–CF4 Gas Mixture

The characteristics of Si etching with electron cyclotron resonance (ECR) plasma of SF6–CF4 are studied in order to improve anisotropy in dry etching using fluoride gases. Si undercutting is decreased by increasing the amount of CF4. Si patterns with vertical sidewalls are obtained with an etch rate of 40 nm/min. Oxygen addition to SF6–CF4 increases Si/SiO2 etching selectivity to more than 10, but does not cause any undercutting. It is concluded that carbon (C) that decomposes from CF4 protects the pattern sidewall from undercutting by fluorine radicals. These results are applied to the anisotropic etching of WSiN as the gate material for GaAs metal-semiconductor field effect transistors (MESFETs). WSiN patterns are more vertical when the chamber inner wall exposed to SF6–CF4 ECR plasma is stainless steel rather than quartz. This is attributed to the reduction of the amount of CO, which possibly forms volatile tungsten-carbonyl [W(CO)6] and, along with fluorine radicals, causes undercutting. It is confirmed that the stainless steel inner wall does not cause serious wafer contamination by metallic elements when WSiN patterns are almost vertically etched.

Analysis of electric field distribution in GaAs metal–semiconductor field effect transistor with a field-modulating plate

Electric field distribution in the channel of a field effect transistor (FET) with a field-modulating plate (FP) has been theoretically investigated using a two-dimensional ensemble Monte Carlo simulation. This analysis revealed that the introduction of FP is effective in canceling the influence of surface traps under forward bias conditions and in reducing the electric field intensity at the drain side of the gate edge under pinch-off bias conditions. This study also found that a partial overlap of the high-field region under the gate and that at the FP electrode is important for reducing the electric field intensity. The optimized metal–semiconductor FET with FP (FPFET) (LGF∼0.2 μm) exhibited a much lower peak electric field intensity than a conventional metal–semiconductor FET. Based on these numerically calculated results, we have proposed a design procedure to optimize the power FPFET structure with extremely high breakdown voltages while maintaining reasonable gain performance.