Using very-low-temperature molecular beam epitaxy growth techniques, an amorphous InGaP layer was deposited to protect the surface during lateral oxidation of an underlying AlGaAs layer. For comparison, other oxidation protection layers such as SiNx and SiO2 were also studied. The oxidized structure consisted of single crystal In0.25Ga0.75As grown on the underlying AlGaAs layer, and then capped with an oxidation protection layer. The oxidation rate of the amorphous InGaP was investigated and compared to the oxidation rates of both single crystal InGaP and GaAs. In addition, the effects of the InGaP layer thickness on the threading dislocation density of the In0.25Ga0.75As layers were investigated. It was found that the amorphous InGaP layers allowed for threading dislocation reduction in the underlying In0.25Ga0.75As layers, while the dielectric protection layers caused an increase in dislocation densities. Atomic force microscopy was also used to investigate the surface after removal of the InGaP protection layers.