Work function of boron-doped polycrystalline SixGe1-x films

The work-function of p-type polycrystalline SixGe1-x films deposited by LPCVD using SiH4 and GeH4 was determined by CV measurements on MOS structures. Boron was introduced in the SixGe1-x films either exsitu by ion implantation or insitu by adding B2H6 in the reactants during film deposition. The work function of the SixGe1-x films is found to decrease as the Ge content increases; it is 5.16 eV for Si, 4.76 eV for Si0.49Ge0.51, and 4.67 eV for Ge. The work function of the Si and Ge films coincides well with that of single crystalline Si and Ge, respectively, It is also found that a thin Si adhesion layer of about 3 nm (nominal thickness), deposited prior to the SixGe1-x, has a negligible effect on the work function determination.