Earlier a technique was developed for thermal GaAs smoothing by annealing in the presence of Ga and As vapors. The vapors were provided in a narrow gap between two GaAs samples, or by annealing in a closed container with a Ga-As melt. At annealing temperatures up to 650°C this technique yielded step-terraced GaAs surfaces. At increased temperatures, the transition from smoothing to kinetic-driven roughening was observed. This roughening revealed itself in the formation of islands (for sublimation) and holes (for growth) of multilayer height and depth. They are formed as a result of step motion through surface areas, where the sublimation and growth did not occur. These spots also act as step stopping centers and lead to step bunching. In this paper we present the results of additional experiments which clarify the reasons of the transition from sublimation to growth (i.e. from islands to holes) in the surface roughening at elevated temperatures. The thermal smoothing technique is further developed to reduce the role of surface roughening. This development allowed us to increase the GaAs smoothing temperature up to 775°C.