The Al_(0.85)Ga_(0.15)As layers buried below the GaAs core layer with and without the SiO_2 layer were successfully oxidized in a wet ambient environment.The experimental results show that the SiO_2 layer has little impact on the lateral-wet-oxidation rate of the Al_(0.85)Ga_(0.15)As layer.The contrast of the SEM image of the oxidized regions and the absence of As-related Raman peaks for samples with the SiO_2 layer arise from the removal of As ingredients with the largest atomic number,which leads to improvements in the thermal stability of the oxidized layer.The PL intensities of samples with the SiO_2 layer are much stronger than those without the SiO_2 layer.The PL emission peak is almost unshifted with a slight broadening under the protection of the SiO_2 layer.This is attributed to the SiO_2 layer preventing oxidation damage to the GaAs capping layer. The experimental results show that the SiO 2 layer has little impact on the lateral-wet-oxidation rate of the Al_ (0.85) Ga_ (0.15) As layer. The contrast of the SEM image of the oxidized regions and the absence of As-related Raman peaks for samples with the SiO_2 layer arise from the removal of As ingredients with the largest atomic number, which leads to improvements in the thermal stability of the oxidized layer. PL intensities of samples with the SiO 2 layer are much stronger than those without the SiO 2 layer. PL emission peak is almost unshifted with a slight broadening under the protection of the SiO 2 layer. This is attributed to the SiO 2 layer prevents oxidation damage to the GaAs capping layer.