FORMATION OF ALUMINUM NITRIDE FILMS ON GAAS(110) AT ROOM-TEMPERATURE BY REACTIVE MOLECULAR-BEAM EPITAXY - X-RAY AND SOFT-X-RAY PHOTOEMISSION SPECTROSCOPY

AlxN1-x films were prepared on GaAs(110) surfaces at room temperature by simultaneous evaporation of aluminum and exposure to a beam of ammonia molecules (reactive molecular-beam epitaxy). The formation of aluminum nitride was followed by using photoemission spectroscopy excited with ZrMζ radiation (hν=151.2 eV). The composition of the deposited films was monitored by recording the N(1s) and Al(2p) core lines excited with MgKα radiation (hν=1253.6 eV). The intensity ratio of these core levels as a function of impinging rate ratio z=ν(NH3)/ν(Al) was compared with the intensity ratio determined with an AlN standard under the same experimental conditions. Aluminum nitride was found to form at room temperature for z values larger than some 104.