We investigate, both experimentally and theoretically, current and capacita
nce (I-V/C-V) characteristics and the device performance of Si/SiO2/Si sing
le-barrier varactor diodes (SBVs). Two diodes were fabricated with differen
t SiO2 layer thicknesses using the state-of-the-art wafer bonding technique
. The devices have very low leakage currents (about 5 x 10(-2) and 1.8 x 10
(-2) mA/mm(2)) and intrinsic capacitance levels of typically 1.5 and 50 nF/
mm(2) for diodes with 5-nm and 20-nm oxide layers, respectively With the pr
esent device physical parameters (25-mm(2) device area, 760-mum modulation
layer thickness and approximate to 10(15)-cm(-3) doping level), the estimat
ed cut-off frequency is about 5 x 10(7) Hz. With the physical parameters of
the present existing III-V triplers, the cut-off frequency of our Si-based
SBV can be as high as 0.5 THz.