SURFACE CHEMICAL BONDING OF SELENIUM-TREATED GAAS(111) A, (100), AND (111)B

The passivation of GaAs(100) by Se prepared in situ has been studied in detail by synchrotron-radiation photoelectron spectroscopy. Deposition of Se on GaAs with the substrate held at room temperature yields As-Se bonding with little reduction of band bending. Few changes are observed both in band bending and chemical bonding as the sample is heated to 250-degrees-C. In contrast, deposition of Se on GaAs at a substrate temperature of around 580-degrees-C gives rise to Ga-Se bonding as Se exchanges with As not only with the surface layer but penetrates into bulk layers as well. Finally, while the interfacial chemistry is similar to a great extent for the (111)A and (111)B surfaces, the uptake of Se in GaAs is found to vary in the following order: (111)A > (100) > (111)B. These results suggest that the Se uptake is controlled by the stability of the terminated atom for the different surface orientations.