We investigate the effect of surface Ga accumulation on the growth of In0.5Ga0.5N by PAMBE at low temperatures (T= 440 °C). We find that the control of the surface metal condition is very important because the crystallization process strongly depends on the metal flux impinging on the surface. The growth rate rapidly decreases when the supply of metal flux exceeds certain amount. Such phenomenon can be explained by the model taking into account droplet effects on the incorporation of metals adatom into the crystal.