Graduation date: 1991The semiconductor gallium arsenide (GaAs) has many potential\ud advantages over the more widely used semiconductor silicon (Si).\ud These include higher low field mobility, semi-insulating substrates,\ud a direct band-gap, and greater radiation hardness. All these\ud advantages offer distinct opportunities for implementation of new\ud circuit functions or extension of the operating conditions of similar\ud circuits in silicon based technology. However, full exploitation of\ud these advantages has not been realized. This study examines the\ud limitations imposed on conventional GaAs metal-semiconductor field\ud effect transistor (MESFET) technology by deviations of the semi-insulating\ud substrate material from ideal behavior. The interaction\ud of the active device with defects in the semi-insulating GaAs\ud substrate is examined and the resulting deviations in MESFET\ud performance from ideal behavior are analyzed.\ud A p-well MESFET technology is successfully implemented which\ud acts to shield the active device from defects in the substrate.\ud Improvements in the operating characteristics include elimination of\ud drain current transients with long time constants, elimination of the\ud frequency dependence of g[subscript ds] at low frequencies, and the elimination of\ud sidegating. These results demonstrate that control of the channel to\ud substrate junction results in a dramatic improvement in the\ud functionality of the GaAs MESFET. The p-well MESFET RF\ud characteristics are examined for different p-well doping levels.\ud Performance comparable with the conventional GaAs MESFET technology\ud is demonstrated. Results indicate that optimization of the p-well\ud MESFET doping levels will result in devices with uniform\ud characteristics from DC to the highest operating frequency
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