The eeciency of single dish mapping and synthesis array mosaicing can be increased by completely sampling the information in the antenna's focal plane. This requires a densely packed array of electrically small elements. Each telescope beam is formed with a weighted combination of signals from seven or more elements. This has the added advantage of correcting for large scale reeector distortion...

Conventional high electron mobility transistors (HFETs) based on AlGaN/GaN heterostructures have been accurately modeled and the results are described in this paper. The Schroedinger's equation and the Poisson's equation have been solved self-consistently in order to obtain a relationship between the sheet carrier density and the applied gate voltage. The relationship is treated using a non-lin...

The large bandgap of gallium nitride (GaN) and aluminum gallium nitride (AlGaN) offers an inherently high intrinsic breakdown field. When the materials are joined into the AlGaN/GaN heterostructure a 2-dimensional electron gas (2DEG) with a high electron density as well as high electron mobility is generated. The combination of high electron density with high mobility and high breakdown field r...

complies with the regulations of the University and meets the accepted standards with respect to originality and quality. During the past two decades AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) have been the target of much attention in high power microwave applications. Crystal imperfections in AlGaN/GaN HFETs have been pointed out as the cause of many reliability concerns such a...

The structure and electronic properties of oxidized (0001) surfaces of GaN grown by plasma-assisted molecular beam epitaxy are investigated by scanning tunneling microscopy/spectroscopy, Auger electron spectroscopy, and first-principles theory. For oxygen exposure at room temperature an amorphous gallium oxide layer is found to form, resulting in a distribution of midgap electronic states exten...

KUANG, WEIWEI. TCAD Simulation and Modeling of AlGaN/GaN HFETs. (Under the direction of Dr. Robert J. Trew and Dr. Griff L. Bilbro). This work focused on the TCAD simulation and modeling of AlGaN/GaN HFETs. AlGaN/GaN HFETs have demonstrated excellent RF performance, which benefits from the high sheet charge density in these hetero-structures, the high carrier mobility and saturation velocity in...

Although accelerated life testing of low noise and power GaAs MESFETs under d.c. bias and RF operation has been conducted, some failure mechanisms remain to be of concern. We will address these concerns and will develop failure models to include AlGaAs/GaAs HFETs. The new set of reliability physics models then will form the starting point for development of physics based failure models for GaN ...

InAIAslInGaAs HFET’s fabricated by conventional mesa isolation have a potential parasitic gate-leakage path where the gate metallization overlaps the exposed channel edge at the mesa sidewall. We have unmistakably proven the existence of this path by fabricating special heterojunction diodes with different mesa-sidewall gate-metal overlap lengths. We find that sidewall leakage is a function of ...

Although accelerated life testing of low noise and power GaAs MESFETs under d.c. bias and RF operation has been conducted, some failure mechanisms remain to be of concern. We will address these concerns and will report on failure models of AlGaAs/GaAs HFETs. The set of reliability physics models then will form the starting point for development of physics based failure models for GaN HFETs devi...

Effects of process flows and device structures on the electrical properties of enhancement mode high electron mobility transistors (HEMTs) are investigated in this work. Except the demonstration of high threshold voltage (Vth) of 4.3V, the process window of the p-GaN residual thickness to ensure a steady operation current was estimated to be 10±5nm in our case. However, to achieve a high breakd...