Hall effective masses, making it difficult to properly assess the value ,of our calculations. There seems to be no obvious way to measure these quantities from d.c. transport measurements. Magneto-kerr effect measurements conducted by Hauge [41], indicate that m* could increase by as much as 31 percent in the range of temperatures from 100 (M*
                                                                 c
0.510 M ) to 300 K. This is i.n reasonable agreement with our calculated
       0
percentage increase in m* in the same temperature range (33 percent), but it is impossible to compare our calculations with Hauge's experimental results, because our effective mass definition was chosen to be mainly applicable to the study of the Hall and conductivity mobility in the low field limit, and this may not apply to the measurements of Hauge [41].

     From'the results of this chapter it can be seen that the approximation of a constant effective mass seems to be inadequate to describe transport properties of holes in silicon above 100 K. There is a substantial increase in the effective mass of holes from 100 to 400-K due to the nonparabolicity of the light-hole band, and a smaller, though not negligible, contribution due to the explicit temperature-dependence and the effects of the split-off band. The validity of this model for the calculation of density-of-states effective mass has been well established [25]. Barber [25] has shown that when the temperature-dependent effective masses are substituted into the theoretical expression for intrinsic carrier density in silicon, the agreement with reported measurements of ni is within the limits of experimental error. Application of this model to theoretical calculation of mobility and resistivity in p-type silicon [17] has provided excellent agreement between theoretical and and experimental values (resistivity with ±6 percent) over a temperature