In/sub 0.425/Al/sub 0.575/As/In/sub 0.65/Ga/sub 0.35/As metamorphic HEMT on GaAs
A /spl delta/-doped In/sub 0.425/Al/sub 0.575/As/ InGaAs metamorphic high electron mobility transistor (MHEMT) has been fabricated successfully and demonstrated. The In/sub 0.425/Al/sub 0.575/As Schottky layer provides good breakdown voltage due to larger energy-gap than that of In/sub 0.52/Al/sub 0.48/As. Experimentally, a high extrinsic transconductance of 277 mS/mm with V/sub DS/ = 2 V and a high drain-source saturation current density of 484 mA/mm with V/sub GS/ =0 V are obtained for a 0.65/spl times/200 /spl mu/m/sup 2/ device at 300 K. Due to good carrier confinement in the channel layer, good pinch-off characteristic can be achieved. The measured f/sub T/ and f/sub max/ for a 0.65 /spl mu/m gate device are 60.5 and 108.5 GHz at V/sub DS/ = 2 V and V/sub GS/ = -1.5V. The NF/sub min/is 0.93 dB at 2.4 GHz, and the associated gain is 23.1 dB.