Hole effective masses of p-type metal-oxide-semiconductor inversion layer in strained Si1-xGex alloys channel on (110) and (111) Si substrates

Abstract

Valence subband properties and hole effective masses of PMOS inversion layer in strained Si1-xGex alloys channel on (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 constant-energy-contours, density-of-states, quantized effective mass in the z-direction m(z), carrier concentration effective mass m(cc), and conductivity effective mass m(sigma) 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 m(cc) the total hole concentration, and subband edges. Our results show that in general m(sigma) in the (110) system is lower than that in the (111) substrate orientation, which implies that (110) Si substrate is more favorable for carrier transport. Furthermore, m(sigma) in the [-110] direction of the (110) Si substrate system are the lightest among all other cases. (C) 2012 American Institute of Physics. [doi :10.1063/1.36845991