Al/sub 0.25/In/sub 0.75/P/Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.35/In/sub /0/sub .65/As graded channel pseudomorphic HEMT's with high channel-breakdown voltage

A new Al/sub 0.25/In/sub 0.75/P/Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.35/In/sub /0/sub .65/As pseudomorphic HEMT where the InAs mole fraction of the Ga
₁
spl minus/x/In/sub x/As channel was graded (x=0.53/spl rarr/0.65/spl rarr/0.53) is described. The modification of the quantum well channel significantly improved breakdown characteristics. In addition, use of an Al/sub 0.25/In/sub 0.75/P Schottky layer increased the Schottky barrier height. Devices having 0.5 μm gate-length showed g/sub m/ of 520 mS/mm and I
_max
of 700 mA/mm. The gate-drain (BV/sub g/spl minus/d/) and source-drain (BV/sub d/spl minus/s/) breakdown voltages were as high as /spl minus/14 and 13 V, respectively. An f
_T
of 70 GHz and f
_max
of 90 GHz were obtained.