Abstract

This paper will describe the development of AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) on SiC for high frequency and high power applications. GaN offers many advantages including high temperature, high breakdown voltage, and high thermal conductivity for high power microwave applications. Previously, work has been mostly focused on HFET or HEMT devices on sapphire substrate. High current and high power potentials have been discussed. High frequency performance (Fmax of about 97 GHz)] and high current density (1.43 A/mm) have been separately shown. The progress mainly came from the improved material quality and the advances in fabrication technology including the reduction in contact resistance. However, owing to the thermal dissipation issue involved with sapphire substrates, the potential for high power microwave devices has not been realized. This paper will discuss the development of microwave GaN HFET and power amplifier effort on SiC. The use of SiC substrate with its high thermal conductivity offers realizable power applications. Again, significant progress has been made recently for HFET on SiC due to the improved material quality and the advances in fabrication technology including the reduction of contact resistance. Specifically, Al0.2Ga0.8N/GaN HFET with an output power of 2.3 W at lOGHz on semi-insulating SiC substrate has been demonstrated. Likewise, with a higher Al content, e.g., Al0.3Ga0.7N/GaN, a higher current capacity with improved ohmic contacts has been attained . We will discuss the progress of materials, technology, device design, and power and noise performance.