The temperature dependence of the conductivity effective mass and
the Hall effective mass is shown in Figures 2.3 and 2.4, with the dopant density equal to 1014 cm3. One consequence of the nonparabolicity of the light-hole band is an increase in the valence band conductivity effective mass as temperature increases from 100 to 400 K. This happens because with increasing thermal energy k0T, more holes reside in the less parabolic regions of the light-hole band. The results plotted in Figure 2.3 show an increase in m* of about 36 percent in this temperature range. The temperature dependence of m* can be attributed mainly to the nonparabolicity of the light-hole band. In the temperature range from 100 to 400 K, m* increases from 0.2850 to 0.5273 m. The slight temperature dependence of m*l and m*l is due to the explicit temperature effect and results in increases of 7.7 percent and 3.76 percent in the m*l and respectively. A larger temperature variation occurs in the case of the split-off band because of the additional effects of the energy displacement at k = 0.
Figures 2.5 and 2.6 show the variation of m* and m* with dopant
density and temperature. For T 2 100 K, m* varies less than 10 percent 14 18 -3
in the dopant density range from 10 to 10 cm . Since the influence of nonparabolicity is reduced in degenerate material [25], it follows as shown in Figures 2.5 and 2.6 that the variation of effective mass with temperature is much stronger at low dopant densities. At lower temperatures there is a much greater change in effective mass due to variations in scattering relaxation time with percentage of ionized impurities.