Since the discovery of continuous, coherent THz radiation from intrinsic Josephson junctions (IJJs) constructed in the single crystals of Bi₂Sr₂CaCu₂O_8+δ in 2007, various types of device structures have been developed. Thermal management of Joule heat in the IJJ mesa structure is the most important issue to improve the radiation characteristics of the IJJ-THz emitters. The radiation frequencies ranging from 0.3 to 2.4 THz, the emission power of $ \sim 30$ pW/mesa and the radiation linewidth of 0.2 GHz at $ \sim 0.5$ THz were obtained from the thermal managed device structures so far. We show a brief overview of the IJJ-THz emitters in our group.