A systematic approach for multidimensional, closed-form analytic modeling: mobilities and effective intrinsic carrier concentrations in p-type Ga1-xAlxAs

The changes in carrier densities of states, band structures, mobilities, and effective intrinsic carrier concentrations n_ie due to high concentration effects of dopants and carriers have been calculated for acceptor densities that span the Mott transition between 10¹⁶cm^-3 and 10²⁰cm ^-3 in p-type Ga_1-xAl_xAs. The theoretical results show that 1) a relative minimum exists in the minority mobility for p-type Ga_1-xAl_xAs 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 A. 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 n_i in GaAs. Because the Mott transition in p-type Ga_1-xAl _xAs 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