ALTERED LAYER COMPOSITION OF SPUTTERED INP (100) WAFER - NONDESTRUCTIVE CONCENTRATION DEPTH PROFILING

Angle-resolved X-ray induced photoelectron spectroscopy (ARXPS) was used in studying the composition of altered layers formed at InP(100) surfaces as a consequence of Xe ion sputtering. To suppress morphological changes, the target temperature was held at 150 K during ion sputtering. Depth concentration profiles were calculated from angle-resolved photoelectron intensities by a unique recently developed numerical method. Altered layers under study were found thicker than the information depth of the method used (approximately 7 nm), inhomogeneous in-depth composition and, in average, indium-rich. The altered layers formed by a ''low'' ion dose were found phosphorus-rich at the top surface and were highly phosphorus depleted beneath the surface. Annealing at 300 K under ultra-high vacuum led to a stoichiometric surface region followed by the phosphorus deficiency in deeper regions. Employing a ''high'' ion dose, the altered layers were less phosphorus depleted and almost homogeneous in composition. Restored depth concentration profiles are compared with results obtained by a common procedure based on a model of semi-infinite solids homogeneous in composition and discussed in the context of preferential sputtering, radiation enhanced diffusion and segregation phenomena.