Hall factor in ultrathin-body silicon-on-insulator n-type metal-oxide-semiconductor field-effect transistors

Hall factor (γH) is investigated experimentally in the ultrathin-body (UTB) silicon-on-insulator (SOI) n-type metal-oxide-semiconductor field-effect transistors (MOSFETs) with the SOI thicknesses (T_SOI) of less than 10 nm. It is demonstrated experimentally for the first time that when T _SOI is thicker than 4.2 nm, γH decreases slightly with a reduction of T_SOI, whereas when T_SOI is thinner than 4.2 nm, γH decreases drastically and becomes almost unity in T_SOI of 2.5 nm. The γH is calculated considering only phonon scattering. Then, calculated γH is compared with γH obtained experimentally. In addition, it is found that in phonon scattering γH is determined dominantly by the intravalley scatterings of the twofold valleys. The dominance of the intravalley scatterings of the twofold valleys in the γH determination is attributed to the energy levels of subbands whereby most of the scatterings are the intravalley scatterings of the twofold valleys.