SiGe virtual substrate HMOS transistor for analogue applications

Silicon–germanium (SiGe) heterojunction metal-oxide-semiconductor field-effect transistors (SiGe HMOSFETs) have been successfully fabricated on Si substrate. The semiconductor heterostructure, which was grown by gas-source molecular beam epitaxy (GS-MBE), was initiated by the deposition of a Si0.7Ge0.3 ‘‘virtual substrate’’. The n-type transistors were fabricated using a standard MOS process. The channel is a thin, undoped layer of strained Si and is buried below an arsenic-doped Si0.7Ge0.3 layer, which provides the carriers. The devices exhibited excellent current–voltage (I–V) characteristics in terms of transconductance and drain current, with no breakdown or leakage. A level-1 model was extracted, for use in circuit design. The results suggest that the realisation of buried-channel SiGe n-HMOSFETs is feasible in MOS processes. These devices are of particular importance in analogue applications