Si delta-doped layers of GaAs were grown by low pressure metal organic vapor phase epitaxy (LP-MOVPE). The results showed that, in LP-MOVPE, growth rate plays a crucial role in confinement of dopants and growth temperature has only a secondary effect. Effects of purge time, doping temperature, and doping period on sheet carrier concentration of delta-doped layers were studied. The effect of growth rate on confinement of dopants was discussed.