Using molecular beam epitaxy (MBE) several layers of GaSb were grown on GaAs at substrate temperatures of 400, 475, and 550 °C, and the surface morphology was studied with aninsituultra high vacuum scanning tunneling microscope (STM). We have observed spiral mound growth of different morphology originating from surface dislocations for the samples grown at 400 and 475 °C, however at 550 °C there is no spiral mound growth and neighboring dislocations are joined by a single step. The surfaces have different rms surface roughness and dislocation density which has important consequences with regard to heterointerface quality. ©1996 American Institute of Physics.