More than 30 years have passed since Fujitsu's announcement of the high electron mobility tran-sistor (HEMT) in 1980." Since then, the HEMT has achieved widespread use as a fundamental technol-ogy driving innovation in the field of information and communications.Applications include satellite broadcasting receivers，mobile phone systems，milli-meter-band automobile radar, GPS navigation systems,and broadband wireless access systems.Furthermore,with a goal to achieve even higher speeds in informa-tion and communication technologies in the future,HEMT Ramp;D is becoming extremely active throughout the world.Today，in addition to conventional gal-lium arsenide (GaAs)HEMTs,the development of ultra-high-frequency indium phosphide (InP)HEMTs2).3)and low-power/high-efficiency gallium nitride (GaN) HEMTs is progressing.
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