Utilizing the diluted magnetic semiconductor ZnMnSe for electron spin alignment near-perfect spin state preparation in semiconductor quantum dots has been demonstrated. We show that the electron spin polarization depends strongly on the electron concentration in ZnMnSe:Cl. Using a model which takes accurately the Zeeman sublevel occupation into account, we can explain well the experimentally observed results. We find that the electron concentration must be below the effective density of states to obtain full electron spin polarization and best device operation. This is especially important in II-VI spin-aligner materials with a low density of states.