Back-Gate Modulation in UTB GeOI pMOSFETs With Advanced Substrate Fabrication Technique

In this paper, the back-gate modulation in ultrathin body germanium-on-insulator (UTB GeOI) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) has been investigated. Based on the direct wafer boding and polishing technique, high-performance 20-nm-thick GeOI pMOSFETs have been fabricated. Peak hole mobility of 158 cm
²
/V · s and high-field mobility (N
_s
= 1 × 10
¹³
cm
^-2
) of 121 cm
²
/V · s are obtained, respectively. The back-gate modulation in UTB GeOI pMOSFETs has been systematically investigated by experiments and simulations. For the case that the back channel does not form, the carrier distributions in the front channel become wider with larger negative back-gate voltage V
_bg
applied. As a result, the mobility increases because of the reduced scattering in the whole N
_s
range. When V
_bg
is negative enough, the back channel forms. In this case, the modulation effect would be strongly affected by the carrier transport properties at the back channel.