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A double-doped metamorphic In/sub 0.35/Al/sub 0.65/As/In/sub 0.35/Ga/sub 0.65/As power heterojunction FET (HJFET) on GaAs substrate is demonstrated. The HJFET exhibits good dc characteristics, with gate forward turn on voltage of 1.0 V, breakdown voltage of 20 V, and maximum drain current of 490 mA/mm. Under RF operation at a frequency of 950 MHz, a power added efficiency of 63% with associated output power of 31.7 dBm is obtained at a gate width of 12.8 mm. This large gate width and state-of-the-art power performance in metamorphic HJFETS were enabled by a selective etching, sputtered WSi gate process and low surface roughness due to an Al/sub 0.60/Ga/sub 0.40/As/sub 0.69/Sb/sub 0.31/ strain relief buffer.
Date of Publication: July 1999