CdI₂ and CdCl₂ doped n-type 90% Bi₂Te₃ 10% Bi₂Se₃ single crystals were grown by the vertical zone melting method, and the thermoelectric properties along the ingot were analyzed. The sharp increase of the Seebeck coefficient and electrical resistivity at the last-to-freeze region were considered as a result of the evaporation of I and Cl from the molten zone. The maximum Figure-of-Merit of the CdI₂ and CdCl₂ doped n-type 90% Bi₂Te₃ 10% Bi₂Se₃ single crystals were 2.7×10^(-3)/K and 2.8×10^(-3)/K, respectively. The higher Figure-of-Merit for the CdCl₂ doped specimens was mainly due to the lower (κ-κ_(el)). The optimum doping amount of CdI₂ and CdCl₂ for n-type 90% Bi₂Te₃-10% Bi₂Se₃ single crystals, grown by the vertical zone melting method, were 0.075-0.10 wt% and 0.04-0.05 wt%, respectively.