Abstract:The effect of wet oxidization of the Al0. 98 Ga0. 02As layer on the thermal stability of devices has been studied in different oxidation conditions. A significant improvement in thermal stability of the oxidized Al0. 98 Ga0. 02As layer has been achieved by lowing the oxidation temperature,prolong the oxidation time and preheating the samp les before the oxidation, which can be used to fabricate reliable devices. The thermal stability is strongly related to the removal of volatile products as evidenced by the Raman spectroscopy.