An AES–ELEED study of the Al/GaP(110) interface

The Al/GaP(110) interface, formed by evaporating Al on a clean, well-ordered, sputter-annealed GaP(110) surface was studied with ELEED and AES. Evidence for island formation, when Al is evaporated on the room-temperature substrate, comes from the slow decrease of the Ga and P AES peaks and the persistence of the substrate ELEED pattern for up to 75 ML (monolayer) of Al. Limited substrate decomposition was also observed for higher rates of Al evaporation. Upon annealing at moderate temperature, Al undergoes a metal–cation replacement reaction whereby Al–P bonds are formed and metallic Ga appears at the surface of the system. With an initial Al coverage of more than 8 ML and a 690 °C annealing cycle, a few layers of AlP are formed.