[en] Different from most of the two-dimensional (2D) topological insulators (TIs) with small bulk band gaps, 2D TIs of Cu₂Te and Ag₂Te have been found to exhibit sizeable bulk gaps with potentials for device applications in room-temperature. Here we have further explored the stability and electronic properties of a lateral heterojunction consisting of Cu₂Te and Ag₂Te. We have found that this heterojunction has buckled geometrical configuration that is dynamically stable, and it is a TI as identified by calculating the Z ₂ topological invariant and the edge states. The band gap of the lateral heterojunction is between those of pristine Cu₂Te and Ag₂Te sheets, and it can be effectively tuned by varying the relative width of the two ribbons in this heterojunction. (paper)