Abstract
The temperature dependence of hole mobility in the silicon inversion layer and its relation to the valence band structure under residual compressive stress are investigated for MOS devices fabricated on (001) silicon films grown on (
012) sapphire substrates. The mobility increases with approximately T-2.14 relationship as temperature decreases. This can be explained by the fact that the fraction of holes in the lower state with high mobility increases with decreasing temperature according to the Fermi-Dirac statistics and surface quantization. Furthermore, density-of-state effective mass is measured to be 0.170∼0.198 m0 for 1 µm-thick SOS film doped with boron, which value is much smaller than that of p-type bulk silicon. This smaller effective mass can be ascribed that light hole mass in the ground state becomes dominate under lateral compressive stress in SOS films.