Breakdown in millimeter-wave power InPHEMT's: A comparison with GaAsPHEMT's

In spite of their outstanding transport characteristics, InP high-electron mobility transistors (HEMT's) deliver lower output power than GaAs pseudomo rphic HEMT's (PHEMT's) throughout most of the millimeter-wave regime, Howev er, the superior power-added efficiency of InP HEMT's when compared with Ga As PHEMT's makes this technology attractive for many applications. The reas on for the relatively inferior power output of InP HEMT's lies in their com paratively small off-state and on-state breakdown voltages, This paper revi ews the state of knowledge regarding the physics of breakdown voltage in In P HEMT's, placing it in contrast with GaAs PHEMT's, It also presents curren t understanding regarding burnout, a closely related phenomenon. This paper concludes by discussing strategies for improving the breakdown voltage and the power output of InP HEMT's.