Development of GaN/AlGaN HEMT's on Silicon Carbide

There is a need for high power solid state devices operating in the millimeter wave frequency range for both radar applications and high frequency communications networks. While GaAs an InP technologies shave demonstrated operation at extremely high frequencies, the power that they can generate is very limited. IN order to replace traveling wave tubes, solid state devices must demonstrate higher operating power levels and higher reliability than have been shown to date. High electron mobility transistors (HEMT's) fabricated with wide bandgap semiconductors such as the GaN/AlN material system have the potential to fulfill this need. The wide bandgap translate into very high operating voltages and very high temperature operation,, which lead to high power levels and high reliability. Silicon carbide (SiC) is the bet substrate for high frequency, high power devices based on GaN because it can handle ten times the power density of a sapphire substrate due to its extremely high thermal conductivity. In addition, the epitaxial film qualities of both GaN and AlN are superior when grown on SiC and this should lead to HEMT's with better frequency response, higher performance and increased reliability.