P= P1 + P2 + P3 (2.24)
thus
m*.= [(m* )3/2 + (m 2 + ,m*3/2 2/3 (2.25)
D Dl Dm2 Dm3J
This combined effective mass is the mass corresponding to the densityof-states of an effective single equivalent parabolic valence band. This concept is useful in calculations where the effective density-ofstates at different temperatures can be calculated from one m*.
The explicit temperature variation of the band curvature is included by assuming that the density-of-states near the band edges varies in a similar manner as the temperature dependence of the energy gap [25]. Thus (m )3/2 is porportional to EGo/EG where EGo is the energy gap at 0 K.
To evaluate the total band equivalent conductivity and Hall effective masses, we assume that in valence band conduction, the total number of holes in motion is equal to the sum of the holes moving on the separate energy surfaces, and that these holes can be modeled as moving on a single spherical energy surface. Thus, the ohmic and the Hall conductivities in the equivalent valence band are given by
aC =CI + 'C2+ 'C3 (2.26)
and
H = Hl + H2 + aH3 (2.27)
respectively.