The Travelling Heater Method (THM) for CdZnTe growth is a widely accepted technique for mass production of detector grade material. Compared to other characterizations of THM grown CdZnTe, study of the growth interface has been neglected in the past. In the present report, large grain/single crystalline as-grown detector grade CdZnTe crystals have been grown by THM technique with diameter up to 52 mm. The crystals were grown from Te solution and the structure of the growth interfaces were investigated for both slow cooled and rapid cooled ingots. The macroscopic shape of the interface was studied and correlated with the grain growth of the ingots. A detailed microscopic morphology of the interface was studied in order to investigate the formation of the Te inclusions at the interfaces.