We have studied the effect of annealing on the atomic intermixing of Zn- and C-doped InGaAs/AlGaAs laser structures. Electrochemical capacitance voltage measurements revealed that the carrier concentration in the Zn-doped GaAs contact layers decreased after annealing at 900 degrees C for 60 s, indicating that some of the Zn acceptors were passivated or outdiffused from the surface, whereas in the C-doped samples there was an increase of the carrier concentration after annealing. This latter was confirmed by X-ray rocking curve results where there was an increase in the amount of lattice contraction associated with the presence of the substitutional carbon C-As after annealing. Secondary ion mass spectroscopy revealed that the Zn diffused significantly from the top layers to the rest of the structures after annealing at 925 degrees C, but the SIMS profile did not change significantly for C-doped samples with annealing. This indicates that Zn has a much higher mobility in comparison to carbon. Photoluminescence measurements after etching the samples to various depths showed similar luminescence defects in both Zn- and C-doped samples. The possible mechanism of atomic intermixing for both Zn- and C-doped samples are discussed.