1TT22
               TI 2 T21


and


       Tji=Taci -I +T      -I +T Ii- + T-N    l                   (3.5)


The total relaxation time in the split-off band is given by


        -3 =       I+ U3     + [ 13- + TN3]                       (3.6)


     Only transitions between the light- and heavy-hole band are considered; the relaxation time Tji takes into account a transition from band i to band j; and Taci' Toi' TIi and T Ni are the relaxation times corresponding to scattering by acoustical phonons, optical phonons, ionized impurities, and neutral impurities respectively, with i as the band index. The procedure for including the nonparabolicity of the band structure into calculations of relaxation time consists of modifying the relaxation time for a given scattering process by replacing the temperature independent effective mass of the parabolic band by the temperature dependent effective mass of the nonparabolic band. This procedure has been successfully applied to the study of acoustic phonon scattering in nonparabolic bands by Radcliffe [18]. Optical phonon and ionized impurity scattering in nonparabolic bands have been considered by Barrie [19] in the same manner. Braggins [1] has used the same method to include nonparabolicity in his study of p-type silicon.   In this work, the relaxation times appropriate to degenerate, parabolic valence bands have been used and modified according to the prescription of Radcliffe [18], Barrie [19], and Braggins [1]. The