Surface morphologies of the molecular beam epitaxy (MBE)-grown GaAs layers using the background-arsenic-pressure-control method were investigated. The growth parameters, such as substrate temperature, growth rate, epilayer thickness, As/Ga ratio, doping concentration substrate type, etc. , are related to the observed oval defect density. Protrusions and Ga-droplets caused oval defects during growth. The origin of the oval defects in our system is found to be the gallium oxide, not Ga 'spitting' from the effusion cell.