The changes in carrier densities of states, band structures, mobilities, and effective intrinsic carrier concentrations nie due to high concentration effects of dopants and carriers have been calculated for acceptor densities that span the Mott transition between 10(16) cm(-3) and 10(20) cm(-1) in p-type Ga1-xAlxAs. The theoretical results show that (1) a relative minimum exists in the minority mobility for p-type Ga1-xAlxAs as a function of acceptor density and (2) the n(ie) values differ by as much as a factor of 2.5 from the intrinsic carrier concentration denoted by ni. In contrast, many commercial device simulators assume that (1) minority mobilities are monotonically decreasing functions of dopant densities and (2) n(ie) values are essentially equal to ni in GaAs. Because the Mott transition in p-type Ga1-xAlxAs occurs near doping densities typically used in the bases of microwave and millimeter wave HBT linear power amplifiers, these results are of technological significance for mobile wireless communications systems and suggest alternative design strategies for improving the performance of HBTs. Published by Elsevier Science Ltd.