A new HZM (horizontal zone melt) grower, using DMF (direct monitoring furnace) with a CCD camera which can provide the in-situ observations of the entire growth procedure as well as the liquid-solid interface, has been developed. Through the HZM technique, a higher yield of the GaAs: In single crystal with low dislocation and good uniformity along the growth direction was obtained. In-situ observation technique of the interface shape during the growth may be applicable to the growth of high quality crystals reproducibly. We confirmed that the incorporation of indium in the crystal has better uniform distribution along the growth axis and the required doping concentration for initiating the "hardening effect" was about 2 × 1019 cm-3 in our growth technique. The electrical uniformity along the growth axis with maximum deviation value of 13% is comparable to that found in most crystals grown by normal freezing method.