A deterministic Boltzmann solver has been developed using a spherical harmonics expansion and is applied to gallium arsenide. The Newton-Raphson scheme is used to solve the nonlinear Boltzmann and Poisson equations. Inclusion of polar optical phonons and their projection onto spherical harmonics is performed. The Pauli exclusion principle is included with the assumption of an isotropic band structure for GaAs. Results are shown for a bulk system and n + -ni-n + structures, which emphasize the impact of the Pauli principle. AC simulations show plasma oscillations of the GaAs devices.