Abstract The temperature induced phase transition of the Ga/Si(1 1 1) surface for submonolayer Ga coverages has been monitored by variable temperature scanning tunneling microscopy. After room temperature deposition of about 1/3 monolayer of Ga on Si(1 1 1), the Si(1 1 1) surface is mostly covered with Ga-induced magic clusters in a 7 × 7 like arrangement whereas at the domain boundary regions of the former Si(1 1 1)-7 × 7 reconstruction an increased density of excess Ga islands is found. The magic clusters are stable against annealing up to 350 °C. At this temperature, however, the Ga-islands coalesce and a mixture of 3 × 3 and 6.3 × 6.3 structures is formed at the domain boundary regions. At an annealing temperature of 400 °C a phase transformation of the 3 × 3 structure to 6.3 × 6.3 is found at the domain boundary region opposite to the usual thermal phase sequence. This can be explained in terms of an interplay of surface kinetics and surface stress.