A key property of nitrides is their large spontaneous and piezoelectric polarization fields that allow significant tailoring of the carrier dynamics and optical properties of nitride devices. In this article, based on first-principles calculations of structural and electronic properties of bulk nitrides and their heterostructures, we investigate the potential of this novel material class for modern device applications by performing self-consistent Monte Carlo simulations. We demonstrate that the internal electric fields have a significant and favorable influence on the transistor characteristics.