Velocity matching of III-V travelling-wave electro-optic modulator structures

A new travelling-wave III-V electro-optic modulator with low loss and a 5% velocity mismatch to the optical wave is analysed using spectral domain analysis. Modulators having a microwave index n/sub mu / of 3.42 have been measured for frequencies up to 26.5 GHz.<>     

Carrier injection into the substrate of GaAs MESFET structures

The temperature analysis of the excess current, flowing in GaAs MESFET's structures after saturation, indicates that carrier multiplication phenomena must occur within the active layer and the interface to cause the substrate current. This current is proportional to VDSrather than tosqurt{V_{DS}}. The negative temperature gradient of the excess current is ten times higher than that of the saturation current. Noise measurements reveal the onset of avalanche.     

Experimental correlation between substrate properties and GaAs MESFET transconductance

The relationship between the characteristics of FET's obtained by direct ion implantation and the properties of a GaAs semi-insulating substrate was investigated. A positive correlation was observed between the dislocation etch-pit density, the as-grown mobility, the mobility after implantation, and the device transconductance. The observation of dislocations' effect on mobility is consistent with the model that dislocations act as segregation centers for imperfections. Localized substrate inhomogeneties are shown to affect the GaAs FET's frequency performance via the mobility.     

Experimental study of carrier transport in multi-layered structures

Gate stress measurements are applied to Flash cell array structures. The counter intuitive V_t shift is associated to the charge redistribution in the ONO layer. This redistribution of charge follows Poole–Frenkel conduction mechanisms. In multi-level Flash, the total charge in the nitride layer need to be minimized, and well-controlled, in order to achieve good data retention of the device.     

Experimental gain and noise figure performance of distributed MESFET amplifiers

The noise figure and gain characteristics of lossless and lossy MESFET distributed amplifiers have been theoretically investigated by various workers. In the letter, in order to support previously reported theoretical results, the experimentally measured noise figure and power gain performance of two-stage and five-stage hybrid microwave distributed amplifiers employing MESFETs are presented. The measured results are compared to theoretically obtained values and found to be in reasonable agreement over most of the band.     

GaAsMMIC双栅MESFET混频器设计与实验研究

对微波单片集成 (简称 MMIC)双栅 MESFET混频器的设计理论和工艺技术进行较为细致的研究。根据双栅 MESFET的理论分析与实验结果 ,建立了一种栅压调制 I- V特性的经验模型 ,推导了双栅 FET混频器变频增益公式。分析了栅压对改变非线性跨导在混频器中的作用。最后设计并加工出了芯片面积为 0 .75 mm× 1 .5 mm Ga As MMIC双栅 FET混频器。     

GaAs MESFET器件低频噪声机理的实验研究

本文介绍了GaAs MESFET器件低频噪声测量系统,以及该器件低频噪声的特点。在分析器件中低频噪声可能来源的基础上,首次采用高能电子辐照技术并结合变温噪声测量、变频C-V等方法,对器件低频噪声产生机理进行了实验研究。     

Monolithic GaAs travelling-wave amplifier

A monolithic GaAs travelling-wave amplifier with distributed input and output lines is described, and its experimental performance in the 0.5?14 GHz range is reported.     

Novel design of travelling-wave FET

In the letter we propose a novel travelling-wave FET, in which an additional image gate is placed beside the drain of the FET as a phase velocity synchroniser. Small-signal analysis is given in the light of coupled wave theory and shows that the device is capable of high gain and wide bandwidth amplification. The easy adjustment of phase synchronisation and compability of the conventional FET fabrication technique make it promising for high-frequency distributed amplification.     

Continuous active T-gate travelling-wave transistor

In the letter experimental results are presented which show that a continuous active gate travelling-wave transistor (TWT) can be used for medium power applications in a wide bandwidth. To reduce the gate resistance, a T-gate configuration has been chosen. This allows one to extend the frequency bandwidth of such a device. Simulations have been performed using small- and large-signal models taking in addition the parasitic capacitances into account. A distributed Schottky diode has been used to adjust the phase synchronisation and therefore to achieve flat gain.<>     

Improved travelling-wave ZnS light modulator

The efficiency of a travelling-wave light modulator has been improved, following an analysis which takes account of electric fringing fields at the edges of the microwave stripline. The predicted modulator bandwidth extends from 40MHz to 15GHz.     

Nonlinear phase behaviour of travelling-wave tubes

An expression is derived which gives the a.m./p.m. conversion factor of a t.w.t. as a function of the helix voltage, when the beam current is varied in such a way as to keep the gain constant.     

Nonlinear models of travelling-wave optical amplifiers

The nonlinear phenomenon in semiconductor travelling-wave optical amplifiers has thus far been studied using a pair of coupled partial differential equations, the wave equation and the rate equation. Simple, small- and large-signal nonlinear models of such amplifiers are presented, which, though obtained from the above equations, are much more suitable for computing the output response associated with arbitrary input signals     

GaN MESFET

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低噪声铝栅MESFET能量烧毁性质的实验分析

本文对铝栅GaAs MESFET的能量烧毁性质作了实验分析.研究了在正脉冲、负脉冲以及各种工作状态下器件的损害情况.实验结果表明,脉冲峰值电压约为30伏时,器件的烧毁能量值集中在0.92至3.6尔格范围内,这表明铝栅GaAs MESFET有较好的抗烧毁性能.     

Effect of carrier injection into MESFET substrates : comparison of MESFET on a semi-insulating buffer,MESFET on a P substrate,and substrate-less MESFET

The carrier injection from the active-layer of the submicron-gate-lengthMesfet into the buffer-layer, or substrate in general, is studied by means of a two-dimensional computer simulation in which the energy conservation equation is simultaneously solved with the carrier conservation equation and Poisson’s equation. The mobility, electron temperature and energy relaxation time are treated as energy dependent parameters. This model is capable of simulating the non-stationary conditions associated with the submicron-gate-length devices. The effect of the carrier injection on the I-V characteristics as well as on the small-signal parameters is investigated by simulating twoMesfet structures; the first is aMesfet on a perfect buffer-layer while the second is a symmetricalMesfet which has no substrate. It is found out that the drain current is increased by the carrier injection, whereas the transconductance is reduced due to the increase of the device dynamic range. TheMesfet with an interfacial potential barrier is also simulated. It exhibits characteristics intermediate between those of the other two devices.     

Packaged double-pass travelling-wave semiconductor laser amplifiers

A novel travelling-wave semiconductor laser amplifier (TW-SLA) proposed previously (1990) was experimentally achieved. The input and output optical signals were transmitted through a single piece of monomode optical fibre which is coupled to the chip of the TW-SLA. An optical circulator was used to separate the two signals.<>     

Single-frequency travelling-wave erbium-doped fibre loop laser

A novel erbium-doped fibre laser cavity configuration with produces single-longitudinal-mode operation with less than 10 kHz linewidth is reported. The fibre laser operates in a travelling-wave mode which prevents spatial holeburning from occurring. A principal advantage of the configuration is that it allows the precise and stable setting of the lasing wavelength.<>     

Comb-type slow-wave structure for travelling-wave masers

A modified comb-type slow-wave structure (s.w.s.) for travelling-wave masers is discussed. The dispersion relation is expressed in terms of the s.w.s. geometry and the admittances of coupled striplines. The slowing factor and the volume-filling factor, important parameters for travelling-wave masers, are discussed.     

Dual-Gate MESFET Mixers

A theoretical and experimental investigation of dual-gate MESFET mixers is presented. Based on a detailed analysis of the different nonlinear modes of DGFET's, a computer-aided modeling procedure has been developed, which allowed to recognize and optimize critical circuit and bias conditions for high conversion gain and IF bandwidth. Theoretical results are in good agreement with experiments on a 12-GHz TV reception mixer with 8-dB conversion gain and 800-MHz bandwidth.