Effects of surface roughness in inversion layer transport

Abstract

The effective mobility of electrons in the inverted Si(100) surface has been measured by a variety of authors over a range of temperatures, gate voltages, back-bias, and doping levels. Generally, it is found that these data are such that the mobility can be unified if plotted against the effective surface normal field Eeff - (QB + Q /2)/esi. It has generally been assumed that sbrface-roughnes s scattering plays a significant role in determining the inversion layer mobility. This latter scattering mechanism depends upon parameters A and L, which have been measured from HRTEM images of the Si/Si02 interface as A = 0.23 nm and L - 1.8 nm. These may then be used to determine the surface-roughness contribution to the mobility. Generally, it is found that this scattering is too weak, and has-500 strong a dependence upon Eeff (varying as Eeff) to impact the inversion layer mobility at room temperature. Instead, we find that the mobility is dominated by the projection of the 3D bulk phonon limited mobility into the surface inversion layer. A simple average technique is proposed which g,i,vfs a power law dependenc8 upon Ee [ p = (Ec/Eef f) I.I with Ec = 2.48 x 10 V/cm] sg that agrees well wi% the measured data.