Intermodulation Distortion Analysis of MESFET Amplifiers Using the Volterra Series Representation

Third-order intermodulation distortion generated in a MESFET amplifer is analyzed by means of the Volterra series representation. A transistor model is used which enables direct analytical determination of the nonlinear elements from small-signal measurements. The four nonlinearities considered are the gate capacitance, transconductance, drain feedback capacitance, and output conductance. Volterra transfer functions are derived for a simplified model and closed-form expressions for the third-order intermodulation ratio and intercept point are determined. The equations show the dependence of distortion on frequency, terminating impedances, and transistor parameters. Principal sources of distortion are identified and the influence of device parameters and network terminations is investigated. Experimental verification on specific MESFET amplifiers, with 2-mu m and 1-mu m gate devices, comparing predicted and measured intermodulation products for various load conditions is presented.     

High-speed, 100+W RF switches using GaAs MMICs

A low-loss, inductive gate bias network structure which allows a very high stacking level of FET devices for high-power RF switching applications is reported. The design, implementation, and performance of S- and C-band SPDT switches based on this structure are described. Multiple GaAs MMIC chips integrated into a suspended-substrate hybrid circuit are used. At S-band, switch risetimes/falltimes of less than 40 ns and an RF power handling capability of 300 W CW have been demonstrated. This input signal level could be maintained during the switch state transitions (hot-switching), while being switched between the two output ports at rates of up to 500 kHz     

单片集成GaAs MESFET微波开关——Ⅱ、宽带单刀单掷和单刀双掷开关电路

本文介绍了单片集成GaAs MESFET微波开关的设计方法和制作工艺.利用空气桥和通孔接地等工艺技术,研制成的调配型宽带单刀单掷开关在0.01～7GHz内,插损为2～3.5dB,隔离度不小于32dB;分布型宽带单刀双掷开关在4.5～7GHz内,插损为1～2dB,隔离度不小于21dB,5GHz下的最大功率容量为3瓦.实验也证实电路的开通时间小于0.6ns.     

Distributed modeling of switching transients in GaAs MESFET's

The transient phenomena resulting from the application of a step bias at the gate electrode of a GaAs MESFET have been simulated using a two-dimensional model. Results emphasizing the effects of the displacement current in high-speed devices are presented. The causes of the delay are discussed for devices of different gate lengths, and the effects of the distributed gate capacitance and the related delay in the drain current characteristics are incorporated in an equivalent circuit model. Analytical expressions derived from large-signal analysis are shown to conform with the results of two-dimensional simulation, allowing for an implementation in simulators such as SPICE     

On-state distortion in high electron mobility transistor microwaveand RF switch control circuits

The origin of the distortion generating mechanism in microwave and RF control circuits using high electron-mobility transistors (HEMTs) is presented in this paper. A model is presented for predicting the distortion in series-connected HEMT switches. The theoretical discussion shows that turn-off voltages in the range of 1.0-1.5 V provide the lowest distortion in series switch configurations. A comparison of the HEMT snitch with MESFET switches shows that the HEMT switch generates more distortion than its MESFET counterpart. In addition, the frequency response of HEMT switches is the opposite of the MESFET switch, with less distortion at low frequencies. The model is validated with experimental data taken on a AlGaAs/GaAs HEMT in the series switch configuration     

宽带GaAs三栅MESFET开关模型

提出一种三栅MESFET开关的模型--附加栅控开关模型,模型是根据三栅MESFET开关器件的结构,考虑了栅极对微波信号的影响,适用于MMIC开关电路的设计,具有很好的宽带微波特性.器件测试值与模型模拟值吻合较好.     

A 12-bit 1-Gword/s GaAs digital-to-analog converter system

The circuitry for a 12-b 1-Gword/s digital-to-analog converter (DAC) IC is described. A DC linearity of /spl plusmn/1/8 LSB has been preserved with this all-depletion GaAs MESFET chip. Dynamic measurements in the frequency domain indicate nonlinearities of less than -62 dBc at a 1-GHz clock rate. The DAC uses a very fast FET analog current switch that exhibits sufficiently low leakage currents for a 12-b linearity. The limited on-chip matching capabilities require the precision DC currents to be generated external to the GaAs chip. A current-switching DAC that partitions the high-speed functions onto a single GaAs chip while the high-precision bit currents are realized off-chip is described. The GaAs chip contains 12 1-b cells, each of which switches an analog bit current into a single sampler circuit that is shared by all the switches. The sampler is used to increase the dynamic linearity in the DAC.     

A low-distortion K-band GaAs power FET

A K-band low-distortion GaAs power MESFET was developed by incorporating a pulse-type channel doping profile using molecular-beam-epitaxial technology and a novel 0.3-μm T-shaped gate. The low-distortion FETs offer about 10 to 15 dBc improvement in second-harmonic distortion compared to devices fabricated on a uniformity doped active layer. Significantly larger power load-pull contours are obtained with the low-distortion devices, indicating the improved linearity of these devices. In an 8-20-GHz single-stage broad-band amplifier, up to 10 dBc improvement in harmonic performance was achieved using the low-distortion device. This low-distortion device exhibits very linear transconductance as a function of the gate bias. A typical 750-μm-gate-width device is capable of 26 dBm of output power with 6 dB of gain, and power-added efficiency in excess of 35% when measured at 18 GHz. At 25 GHz, the device is capable of 24 dBm of output power with 5 dB associated gain     

Full band Monte Carlo simulation of zincblende GaN MESFET'sincluding realistic impact ionization rates

In this paper, we present the first theoretical study of the breakdown properties of zincblende phase GaN MESFET devices. The calculations are made using a full band, ensemble Monte Carlo simulation that includes a numerical formulation of the impact ionization transition rates. The breakdown voltage, transconductance and cutoff frequency are calculated for the GaN MESFET under two different conditions, with and without semiconductor-oxide interface states. Uniform surface depletion regions model the effect of the interface states. It is found that the breakdown voltage of the zincblende GaN MESFET is less dependent upon the surface depletion conditions than a corresponding GaAs MESFET. It is also found that the drain current increases more gradually with increasing drain-source voltage at the onset of breakdown and that the breakdown voltage of the zincblende GaN MESFET is predicted to be several times larger than that of a comparable GaAs MESFET. The maximum current gain cutoff frequency of a 0.1 μm gate length GaN MESFET is calculated to be 230 and 220 GHz, for the non-surface-depleted and the surface depleted devices respectively     

Comparison of GaAs MESFET and GaAs p-i-n diodes as switch elements

The Kurokawa-Schlosser quality factor Q̂ is used to compare the GaAs MESFET switch with the GaAs p-i-n diode switch. The MESFET device parameters are governed by the power handling capability and the specified pinchoff voltage, and the switch Q̂ is calculated from an approximate expression. The GaAs p-i-n has been characterized using a simple diode model which is derived from detailed simulations. The comparison for typical devices shows that the GaAs pin has the higher Q̂ and therefore should have improved characteristics as a switch in terms of insertion loss and isolation.     

A new GaAs power MESFET structure for improved power capabilities

A GaAs microwave power MESFET structure is described that achieves a significant improvement of the gate mode attenuation by incorporating a suitably terminated transmission line parallel to the gate. The reduced attenuation allows a much wider single gate (a factor of 4 is possible) and a corresponding improvement of the total output power. It is shown that this approach leads to higher gain and cutoff frequency. An additional advantage of this MESFET structure is its higher input resistance relative to a device with equal total gate width but more gates in parallel. This results in simpler matching circuits of greater bandwidth. The single-gate structure can be connected in parallel to further increase the total output power. The results of an electrical characterization of the devices are presented, and its advantages and potential application are discussed     

The Schottky-gated hall-effect transistor and its application to carrier concentration and mobility profiling in GaAs MESFET's

A special four-terminal MESFET (HFET) is employed in a unique way to characterize carrier concentration and mobility profiles of channel implants into GaAs. This device allows measurement of carrier concentration and mobility under forward gate bias so that the near surface region within the zero bias depletion width can be profiled. From the carrier concentration and mobility profiles, surface and bulk effects can be distinguished. This characterization method allows test devices to be built on production wafers and therefore can serve as a process monitor in the fabrication of GaAs IC's.     

Co-integration of GaAs MESFET and Si CMOS circuits

Co-integration of GaAs MESFET and Si CMOS circuits is demonstrated using GaAs-on-Si epitaxial growth on prefabricated Si wafers. This is thought to be the first report of circuit-level integration of the two types of devices in a coplanar structure. A 2-μm gate Si CMOS ring oscillator has shown a minimum delay of 570 ps/gate, whereas on the same wafer a 1-μm gate GaAs MESFET buffered-FET-logic (BFL) ring oscillator has a minimum delay of only 70 ps/gate. A composite ring oscillator consisting of Si CMOS invertors and GaAs MESFET invertors connected in a ring has been successfully fabricated     

8～20GHz GaAs pin二极管单片单刀双掷开关

基于中国科学院微电子研究所的GaAs pin二极管工艺,设计、制作并测试了一种单片单刀双掷开关.在8～20GHz频段内,开关正向导通时的插人损耗最小值为1.5dB,输入和输出端的同波损耗大于10dB;开关关断状态的隔离度最大值为32dB.开关的支路采用串联-并联-并联的结构,其中的GaAs pin二极管基区厚为2.5μm.在1.3V的偏置电压下,正向导通的串联二极管工作电流为     

2.9 V operation GaAs power MESFET with 31.5-dBm output power and64% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.9 V has been developed using the high-low doped channel structure grown by molecular beam epitaxy. The device has 0.6 μm gate length and 16 mm gate width. The power performance tested at a 2.9 V drain bias and 900 MHz operation frequency was output power of 31.5 dBm with 11.5 dB gain and 64% power-added efficiency     

Determination of energetic distribution of interface states betweengate metal and semiconductor in sub-micron devices from current-voltagecharacteristics

Density and energetic distributions of interface states between metal-semiconductor rectifying contacts in sub-micron GaAs MESFET and AlGaAs/InGaAs pseudomorphic high electron mobility transistors (HEMT's) have been studied. Electrical properties of the interface states between gate metal and semiconductor in sub-micron devices depend on growth technique, associated processing parameters and surface states on III-V semiconductors. Correlation between nonideal current-voltage (I-V) characteristics and interface states has been established through the bias dependence of ideality factor. Ideality factor determined from I-V characteristics of MESFET and HEMT increases with bias and then decreases after reaching a maximum. A theoretical model based on nonequilibrium approach has been used to determine the density of interface states and their energetic distribution from ideality factor. Essentially, Fermi level shifts with applied bias and Schottky barrier height changes due to trapping and detrapping of electrons by the interface states, and from these changes, density of interface states and their energetic distributions have been determined     

半绝缘非掺GaAs材料制备的MESFETs背栅效应

设计了一套适用于二种工艺（离子注入隔离工艺和半绝缘衬底自隔离工艺）的背栅效应测试版图,用选择离子注入形成有源层和欧姆接触区,在非掺杂的半绝缘ＧａＡｓ衬底上制备ＧａＡｓＭＥＳＦＥＴｓ器件．研究了这二种不同工艺制备的ＭＥＳＦＥＴｓ器件的背栅效应以及不同距离背栅电极的背栅效应大小．结果表明,采用离子注入隔离工艺制备的ＭＥＳＦＥＴｓ器件的背栅效应要比采用半绝缘衬底自隔离工艺制备ＭＥＳＦＥＴｓ器件的背栅效应小,背栅效应的大小与距离近似成反比,采用隔离注入的背栅阈值电压随距离变化的趋势比采用衬底自隔离的更大．     

GaAs microwave MOSFET's

GaAs microwave metal-oxide-semiconductor field-effect transistors (MOSFET's) with plasma-grown native oxides as gate insulator have been fabricated using a low-temperature magnetically controlled plasma-oxidation technique. A small-signal enhancement device with the gate length of 2.0 µm has demonstrated useful unilateral power gains in the 2-8-GHz frequency range. A maximum frequency of oscillation in the enhancement device is 13 GHz. This is the highest in all enhancement-mode GaAs devices reported up to this time. A medium-power depletion device with the gate length of 1.8 µm has the maximum frequency of oscillation of 22 GHz. This value is 10 percent larger than that of the best analogous metal-semiconductor field-effect transistor (MESFET). The intrinsic current-gain cutoff frequency for the depletion MOSFET is 4.5 GHz which is 22 percent higher than that of the MESFET. The superiority of the depletion MOSFET in the small-signal microwave performance over the MESFET results from the smaller gate parasitic capacitance in the MOSFET as compared to the MESFET. The depletion MOSFET has produced 0.4-W output power at 6.5 GHz as a Class A amplifier. Quite a large frequency dispersion of transconductance is observed in the enhancement MOSFET at a frequency range between 10 and 100 kHz and attributed to interface states. The effect of the interface states does not severely restrict the microwave-frequency capabilities of the enhancement MOSFET as well as the depletion MOSFET since the interface states are unable to follow the input-signal variations at high frequencies.     

A Low Distortion and Low Dissipation Power Amplifier with Gate Bias Control Circuit for Digital/Analog Dual-Mode Cellular Phones

A power amplifier operating at 3.3 V. has been developed for CDMA/AMPS dual-mode cellular phones. It consists of linear GaAs power MESFET's, a new gate bias control circuit, and an output matching circuit which prevents the drain terminal of the second MESFET from generating the harmonics. The relationship between the intermodulation distortion and the spectral regrowth of the power amplifier has been investigated with gate bias by using the two-tone test method and the adjacent channel leakage power ratio (ACPR) method of CDMA signals. The dissipation power of the power amplifier with a gate bias control circuit is minimized to below 1000 mW in the range of the low power levels while satisfying the ACPR of less than ?26 dBc for CDMA mode. The ACPR of the power amplifier is measured to be ?33 dBc at a high output power of 26 dBm.     

High-performance In0.08Ga0.92As MESFETs onGaAs(100) substrates

In_0.08Ga_0.92As MESFETs were grown in GaAs (100) substrates by molecular beam epitaxy (MBE). The structure comprised an undoped compositionally graded In_xGa_1-x As buffer layer, an In_0.08Ga_0.92As active layer, and an n⁺-In_0.08Ga_0.92As cap layer. FETs with 50-μm width and 0.4-μm gate length were fabricated using the standard processing technique. The best device showed a maximum current density of 700 mA/mm and a transconductance of 400 mS/mm. The transconductance is extremely high for the doping level used and is comparable to that of a 0.25-μm gate GaAs MESFET with an active layer doped to 10¹⁸ cm^-3. The current-gain cutoff frequency was 36 GHz and the power-gain cutoff frequency was 65 GHz. The current gain cutoff frequency is comparable to that of a 0.25-μm gate GaAs MESFET