Over the past few years, systems based on gallium nitride high-electron-mobility transistors (GaN HEMTs) have increasingly penetrated the markets for cellular telephone base stations, RADAR, and satellite communications. High power (several W/mm), continuous-wave (CW) operation of microwave HEMTs dissipates heat; as the device increases in temperature, its electron mobility drops and performance degrades. To enhance high-power performance and enable operation in high ambient temperature environments, the AlxGa1[-]xN/GaN epitaxial layers are attached to polycrystalline diamond substrates. e lower surface temperature rise on GaN-on- diamond is directly measured; subsequently, improved electrical performance is demonstrated on diamond versus the native (Si) substrates. Benchmark AlxGa1[-]xN/GaN devices are fabricated on SiC for comparison to diamond, Si, and bulk GaN substrates; the merits and performance of each is compared. In collaboration with Group4 Labs, X-band amplifier modules based on GaN-on-diamond HEMTs have been demonstrated for the first time. Recent efforts have focused on substituting AlxIn1[-]xN barriers in place of AlxGa1[-]xN to achieve higher output power at microwave frequencies and addressing the challenges of this new material system. Ultimately, these techniques may be combined to attain the utmost in device performance.

"Compound semiconductor gallium nitride high electron mobility transistors (HEMTs) have significant potential for use in the electronics industry, including radar applications and microwave transmitters for communications. These wide band gap semiconductors have unique material properties that lead to devices with high power, efficiency, and bandwidth compared with existing technologies. In this work, the electrical properties of gallium nitride HEMTs on silicon substrates were studied in the context of drain characteristics and breakdown voltage. The design, fabrication, and characterization of different devices are presented, in addition to a discussion on the effects of annealing and different gate contact materials. While demonstrating considerable promise in the field of high power radio frequency (RF) applications, this technology is yet immature and several fabrication issues still need to be addressed. The goal of this work is to represent a stepping stone in further developing this technology to be used in high power devices." --

The unique materials properties of GaN-based semiconductors have stimulated a great deal of interest in research and development regarding nitride materials growth and optoelectronic and nitride-based electronic devices. High electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown field, and low thermal impedance of GaN-based films grown over SiC or bulk AlN substrates make nitride-based electronic devices very promising. The chemical inertness of nitrides is another key property.This volume, written by experts on different aspects of nitride technology, addresses the entire spectrum of issues related to nitride materials and devices, and it will be useful for technologists, scientists, engineers, and graduate students who are working on wide bandgap materials and devices. The book can also be used as a supplementary text for graduate courses on wide bandgap semiconductor technology.

"Gallium nitride (GaN) high electron mobility transistors (HEMTs) have a potential in electronic fields such as broadband communication and radar applications. GaN possesses many advantages including a direct and wide bandgap, making GaN HEMTs ideal to high voltage and high temperature. Experiments have yielded devices with high power output efficiency and bandwidth compared to other modern transistor devices. In this work, GaN HEMTs on silicon substrates with various gate lengths have been designed and fabricated. The current-voltage characteristics and breakdown voltages of the HEMTs have been measured. The design, fabrication, and characterization of different devices were presented, as well as the measurements and discussion of devices under effects of heat treatment. Although the fabrication technology is still immature and under development, GaN HEMTs have shown promising results in radio frequency, high power, and wireless power transfer applications. The goal of this work is to investigate the electrical properties of the GaN HEMTs and to develop this technology in high power devices in the future." --