Abstract
The dissolution rates of III-V semiconductors GaAs and InP were determined by the inductively coupled plasma technique. In this work, the compounds of the solid oxide layer on p-type GaAs and InP were identified at room temperature by both X-ray wide angle diffraction and glancing angle diffraction. A 12 kW rotating Cu anode X-ray source ensured high sensitivity, not only to investigate chemical composition, but also to characterize the structural features of the oxides. The GaAs dissolution rate in aqueous H2SO4 solutions increased dramatically in the presence of H2O2, and the GaOOH phase was uniquely found on the oxidized surface. In contrast, the dissolution rate of InP and GaAs in aqueous H2SO4 was severely restricted even in the most acidic solutions under illumination, about 3-order lower when compared with GaAs in H2SO4/H2O2/H2O solution and no GaOOH compound was formed on the surface of GaAs. The differences in their reactivities can be interpreted in terms of the energetic tendency in the stability of GaOH2+ intermediate in H2O2 and in H2O, which, in turn, determine whether or not the formation of GaOOH on GaAs surface. It is postulated that the production of GaOH2+ intermediate is thermodynamically favored so that the dissolution rate of GaAs in H2SO4 system is accelerated by the present of H2O2. By combining the etching rate and X-ray diffraction results it is possible to show that H2O2 play a critical role in the etching of GaAs in H2SO4 solution.