Gallium nitride based high power heterojunction field effect transistors: Process development and present status at UCSB

The development of GaN based devices for microwave power electronics at the University of California, Santa Barbara (UCSB), is reviewed, From 1995 to 2000, the power performance of AlGaN/GaN on-sapphire heterojunction field e ffect transistors improved from 1.1 W/mm to 6.6 W/mm, respectively. Compens ating the disadvantages of the low thermal conductivity of the sapphire sub strate through heat management via flip chip bonding onto AIN substrates, l arge periphery devices with an output power of 7.6 W were demonstrated. UCS B also fabricated the first GaN based amplifier integrated circuits, Critic al issues involved in the growth of high quality AlGaN/GaN heterostructures by metal-organic chemical vapor deposition and the device fabrication are discussed.