| Summary: | 博士 === 國立中興大學 === 物理學系所 === 100 === Valence subband properties and hole effective masses of MOS inversion layer in strained Si1-xGex alloys channel on (001), (110), and (111) Si substrates are studied theoretically based on the Luttinger-Kohn Hamiltonian. The subband structures under investigation are a result of the quantized levels produced by the triangular quantum well in the inversion layer created by the applied gate bias in the z-direction. Valence subband properties including equal energy lines, density-of-states, quantization effective mass in the z-direction mz, carrier concentration effective mass mc, and conductivity effective mass are calculated as functions of the Ge concentration at gate electric field of 1 MV/cm. An analytic expression for the Fermi level is derived in terms of mc, the total hole concentration, and subband edges. Our results show that in general in the (110) system is lower than that in the (111) and (001) substrate orientation, which implies that (110) Si substrate is more favorable for carrier transport. Furthermore, in the y, [-110], direction of the (110) Si substrate system are the lightest among all other cases. In the last section, we directly calculate the alloy limited hole mobility in different orientation surface with Ualloy=0.2 and 0.7 eV for comparisons. Finally, we calculate the phonon-alloy scattering hole mobility as a function of gate electric fields and calculate the relaxed Si1-xGex alloy cases for comparing the strained alloy cases in the (001) system.
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