Electrical Properties of Ultra-Thin Body (111) Ge-On-Insulator n-Channel MOSFETs Fabricated by Smart-Cut Process

We have systematically examined electrical characteristics of ultra-thin body (UTB) (111) Ge-on-insulator (GOI) n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs) fabricated by the smart-cut process and have compared their electrical properties with those of (100) ones. The (111) GOI thickness was varied from 29.4 to 7.3 nm. The normal MOSFET operation of a 7.3 nm-thick (111)-oriented GOI nMOSFET has been demonstrated with a reasonable ON/OFF ratio of 10
⁴
. However, degradation in the effective electron mobility and subthreshold swing (SS) of the (111) GOI nMOSFETs with decreasing the GOI thickness ( T
_GOI
) was observed. Raman analyses and electrical characteristics of GOI nMOSFET under back-gate operation has suggested that a high interface state density at (111) GOI/buried oxide interfaces as well as low GOI film quality near the back interfaces can be an origin of this degradation of the electrical properties with thin body channels.