Abstract-This paper reports the studies of the inversion layer mobilities in n-channel MOSFET's fabricated on Si wafers with three surface orientations ((loo), (110), and (111)) from the viewpoint of the universal relationship against the effective field, E,R(= q(A\-clpl + 11 . -Vh)/~Si). It is found that the universality does hold for the electron mobilities on (110) and ( l l l ) , when the value of 17 is taken to be 113, different ftom the electron mobility on (loo), where I ) is 1/2. Also, the E,ff dependence of the electron mobility is found to differ among (loo), (110), and (111) surfaces. This is attributed to the differences in the E v~ dependence of the mobility limited by surface roughness scattering among the orientations.The origins of E, m and '1 are discussed on the basis of the relaxation time approximation for a 2DEG (2-dimensional electron gas). While the surface orientation dependence of 11 in phonon scattering can be understood in terms of the subband occupation, it is found that the theoretical formulation of surface roughness scattering, used currently, needs to be refined in order to explain the differences in E,ff dependence and the value of 11 among the three orientations.

This paper reports the studies of the inversion layer mobilities in n-channel MOSFET's fabricated on Si wafers with three surface orientations ((loo), (110), and (111)) from the viewpoint of the universal relationship against the effective field, E,R(= q(A\-clpl + 11 .-Vh)/~Si). It is found that the universality does hold for the electron mobilities on (110) and (l l l) , when the value of 17 is taken to be 113, different ftom the electron mobility on (loo), where I) is 1/2. Also, the E,ff dependence of the electron mobility is found to differ among (loo), (110), and (111) surfaces. This is attributed to the differences in the E v~ dependence of the mobility limited by surface roughness scattering among the orientations. The origins of E, m and '1 are discussed on the basis of the relaxation time approximation for a 2DEG (2-dimensional electron gas). While the surface orientation dependence of 11 in phonon scattering can be understood in terms of the subband occupation, it is found that the theoretical formulation of surface roughness scattering, used currently, needs to be refined in order to explain the differences in E,ff dependence and the value of 11 among the three orientations.

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