Gate bias symmetry dependency of electron mobility and prospect of velocity modulation in double-gate silicon-on-insulator transistors

We report on detailed room-temperature transport properties of a 17nm thick double-gate silicon-on-insulator (DGSOI) transistor. We find that when the electron gas is transferred between the top and the bottom of the silicon-on-insulator (SOI) layer by changing the gate bias symmetry (i.e., applying the gate biases in a push–pull fashion), while keeping the carrier density constant the maximum mobility occurs when the electron gas symmetrically occupies the whole SOI slab. The observed mobility behavior is the fingerprint of volume inversion∕accumulation. This gate bias symmetry dependency of the mobility suggests that DGSOI devices intrinsically can be operated in a velocity modulation transistor (VMT) mode. In the experimental gate bias window, the maximum velocity∕mobility modulation is ∼40%. The VMT transconductance exceeds conventional single-gate transconductance when electron density is above ∼5.3×1016m−2. Improvements of the observed VMT operation in thin DGSOI devices are discussed.