The general relationship between average mobility of carries and average conductivity in a doped layer with an arbitrary impurity distribution has been established.Assuming that all impurities have been ionized

the formulas of the relationship between average mobility of carriers and parameters of doping in the sub-diffused layers have been derived for complementary error and Gaussian impurity concentration distribution. The formulas can be extensively used to any semiconductor materials. The average mobility value of carriers in the Si sub-diffused layers as a function oE surface concentration have been calculated by means of Irvin’s curves. The results are shown graphically for engineering application. The expressions for sheet resistivity of sub-diffused layers in terms of average mobility of carriers are analysed and discussed. It is found that

if the surface concentration is one order of magnitude larger than the background concentration

the average mobility of carriers in all-diffused layers depends only on the surface concentration

and it can be approximately represented byThe curves which are directly used to determine surface concentration from measured sheet resistivity-value are achieved. Considering the nonhomogeneous diffused layers

the design formulas for squeezed resistance in integrated circuits and base resistance in transistors are represented by average mobility of carriers.