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SiGe/Si n-type modulation doped field effect transistors (MODFETs) fabricated on sapphire substrates are characterized at microwave frequencies for the first time. The highest measured room temperature electron mobility is 1380 cm2/V-sec at a carrier density of 1.8×1012 cm-2 for a MODFET structure. At room temperature, a two finger, 2×200 micron gate n-MODFET has a peak transconductance of 37 mS/mm at a drain-to-source voltage of 2.5 V and an fmax of 2.45 GHz. Microwave performance of the transistor improved with decreasing temperatures, with an fmax= 5.25 GHz at 100 K.
Date of Conference: 8-10 Sept. 2004