Exciton-polaritons are hybrid light-matter quasiparticles. They are composite and interacting bosons which can condense dynamically in a singleparticle ground state via stimulated scattering. The formation of exciton-polaritons under electrical pumping has been demonstrated in quasi two dimensional systems [1-3]. In this work, we discuss the non-linear polariton emission caused by stimulated scattering in micropillar cavities under electrical pumping . We distinguish our polariton laser from a conventional cavity mediated laser by probing it in a magnetic field. While a characteristic Zeeman-splitting is present in the regime of polariton lasing [4,5], it is fully absent when the device enters the weak coupling regime.