THE INVESTIGATION ON THE STRUCTURAL DISTRIBUTION OF PASSIVATED GAAS(100) SURFACE AFTER (NW4)(2)S-X TREATMENT

The qualitative and quantitative structural distribution of HCl- and/o r (NH4)(2)S-x-treated GaAs surface was investigated by angle-resolved X-ray photoelectron spectroscopy. Carbon contamination and elemental A s layers were observed in HCl-treated GaAs surface. The (NH4)(2)S-x tr eatment following HCl led to the elemental As replacing the As-S bond. Compared with HCl treatment, the more rugged oscillation of photoelec tron intensity of Ga and As was observed according to take-off angle i n (NH4)(2)S-x-treated GaAs due to the periodic arrangement of S-passiv ation layer. The quantitative depth distribution of surface constituen ts was derived by processing the experimental angular profile and comp aring with a simplified layer model. Out results indicate that the dis tributing order of surface layer on GaAs substrate is a C layer of 5.8 1 +/- 0.54 Angstrom and elemental As layer of 4.57 +/- 0.40 Angstrom w ith HCl treatment, and a C layer of 5.71 +/- 0.52 Angstrom and S-passi vation layer (As-S) of 4.73 +/- 0.30 Angstrom with (NH4)(2)S-x treatme nt from the surface. Through the analysis of low-energy electron diffr action, the elemental As after HCl treatment was revealed to be random ly distributed and the passivated GaAs surface showed (2 x 1)-reconstr ucted structure at room temperature with regular distribution of As-S bonds. (C) 1998 Elsevier Science S.A.