Thermal wet oxidation of GaP and Al0.4Ga0.6P

Thermal wet oxidations of GaP and Al0.4Ga0.6P at 650 degrees C for various times have been performed. Comparisons are made on oxidation rates and post oxidation morphology. Transmission electron microscopy shows that when oxi dizing GaP, polycrystalline monoclinic GaPO4. 2H(2)O forms without noticeab le loss of phosphorus. Oxidation for 6 h or more leads to poor morphology r esulting in cracks and detachment. A thickness expansion of about 2.5-3 tim es is noticed as a result of oxidation. In contrast, oxidized Al0.4Ga0.6P e xhibits much better morphology without cracks or detachment from the substr ate. The oxide has an almost amorphous-like microstructure. The oxidation p rocess shows typical diffusion-limited reaction at long anneals. Preliminar y work on the oxidation of AlP indicates that the reaction leads to formati on of Al2O3 and possible volatile P2O5 diffusing out of the specimen. Thus, from the structural viewpoint, AlGaP forms a better oxide suitable for dev ice needs. (C) 2000 American Institute of Physics. [S0003-6951(00)02228-2].