Gaas Circuit Of The Gaas Mesfet Devices And Optical Communication

GaAs devices and circuits have some distinct advantages such as high speed, low power dissipation, low noise, wide operation temperature and high radiation hardness. The applications of GaAs include fiber optic communication, satellite communication, super high speed computer, high speed test instrument, mobile communication, etc. In recent years, the development of fiber optic communication has been the driving force of GaAs IC抯 growth. With the increase of the integration of GaAs IC, the research of the threshold voltage uniformity is becoming more and more important. The models of GaAs MESFET have been discussed. The drain current-voltage relations have been derived from two region model. But the complex calculation and the changing process make the physical model be unsuitable for circuit simulation. So the Curtice model and the Statz model in SPICE or PSPICE circuit simulation program is most widely used for GaAs IC design. It is found that the Statz model is better. A test structure for measurement of the threshold voltage uniformity has been designed. In order to get the influence of different process on the threshold voltage uniformity, GaAs MESFETs are fabricated in recessed-gate process and planer selectively implanted process. The results show that the threshold voltage uniformity using planer selectively implanted process is better. The influence of different process on sidegating effect of GaAs MESFET has been studied using recessed-gate process, planer selectively implanted process and planar boron implanted process. The results show that the sidegating threshold voltage is higher when adjacent devices are isolated by boron implantation, which means that boron implantation significantly improves the electrical isolation between devices and reduces the sidegating effect. We also studied some characteristics of sidegating effect using planar boron implanted process including photosensive, hysteresis, influence of sidegating effect on MESFET threshold voltage, influence of drain-source voltage on sidegating threshold voltage, influence of exchanging drain and source electrode on sidegating threshold voltage, relation between sidegating threshold voltage and the distance of side-gate and MESFET, relation between sidegating effect and floating gate, and so on. A threshold voltage auto-test system has been set up which can automatically get the threshold voltage of MESFET on semi-insulating GaAs crystal. The test sample may be D2 inch, D3 inch, or other size less than cD3 inch. Useful results can be gotten from this system such as data of threshold voltage, the mapping of threshold voltage, statistic average value and standard deviation of threshold voltage, etc. This system is the frist and the only GaAs threshold voltage auto-test system of the nation and it is significant for promoting the research of the relation between threshhold voltage uniformity and GaAs materials made in our country. A super high-speed GaAs decision circuit applied to 2.5Gb/s fiber optic communication has been designed. The monolithic GaAs decision circuit with 1~.tm depletion-mode GaAs MESFET抯 is fabricated. It is proved by PSPICE circuit simulation and test that the circuit can deal with input signal rightly and produce correct digital output signal. The circuit can operate at 2.8Gb/s, so it can be applied to 2.5Gb/s fiber optic communication. A super high-speed GaAs clock recovery circuit applied to 2.5Gb/s fiber optic communica...