QUANTITATIVE ARXPS DEPTH PROFILING CHARACTERIZATION OF NATIVE OXIDES GROWN ON IN0.53GA0.47AS(100) SINGLE-CRYSTALS

We report the results of an angle-resolved X-ray photoelectron spectro scopy (ARXPS) quantitative study of room-temperature native oxides on LPE grown In0.53Ga0.47As(100). ARXPS is a powerful non-destructive exp erimental technique for identifying chemical species and following com positional variations close to the surface (less than 100 angstrom of thickness). Such investigations can be of relevance for understanding the growth mechanism, competition between different cations with respe ct to oxidation, and surface damage due to the degradation process. In this approach a model of photoemission from a planar InGaAs bulk cove red with two homogeneous overlayers (representing an oxide and a degra dation region) constitutes the basis of the computer-aided ARXPS analy sis. The thickness and the composition of the two overlayers are the p arameters of a curve fitting, based on the Laplace transform of step-l ike profile functions, of the experimental data taken at different pho toelectron escape angles. Our results indicate the presence of non-sto ichiometric oxides lacking oxygen with respect to In(OH)3, Ga2O3 and A s2O3, respectively. An oxide layer about 9 angstrom thick is detected on the top of the original surface and is composed of 66% indium hydro xide, 31% arsenic oxide and 3% elemental arsenic. The following inner region corresponds to a diffuse interface oxide/substrate about 12 ang strom thick, containing 41% GaAs, 28% gallium oxide, 28% indium hydrox ide and 3% InAs. Finally, the composition of the substrate agrees with the nominal composition of the epitaxially grown crystal. These resul ts indicate a preferential oxidation of InAs with respect to GaAs and suggests that the driving force of the oxidation process is the bindin g energy difference of the two binary compounds constituting the cryst al.