Si/SiGe FETs grown by MBE on a LEPECVD grown virtual substrate

This paper reports on the preparation and assessment of Si/SiGe based n-type field-effect transistors (n-FET). The layer growth was carried out in a two step epitaxy procedure. First. a strain-relieved SiGe layer with a final Go fraction of 40% was deposited oil a Si(100) wafer by means of low energy plasma enhanced chemical vapor deposition (LEPECVD). On this virtual substrate the active layer stack was grown by molecular beam epitaxy (MBE) consisting of a 9 nm thick strained Si channel sandwiched between Sb modulation doped Si0.6Ge0.4 cladding layers. The samples were structurally analyzed by atomic force microscopy (AFM). X-ray diffraction (XRD). and cross-section transmission electron microscopy (XTEM). FET structures were prepared and electrically characterized by conductivity and Hall measurements and by recording DC characteristics. Electron Hall mobilities as high as 760 cm(2) V(-1)s(-1) at a carrier density of 7.6 x 10(12) cm(-2) has been obtained at room temperature (RT). A maximum transconductance of 230 mS mm and a drain saturation current of 230 mA mm(-1) have been achieved. (C) 2002 Elsevier Science B.V. All rights reserved.