Nitridation of the GaAs(001) surface: Thermal behavior of the (3x3) reconstruction and its evolution

The nitridation of the GaAs(001) surface using a radio frequency atomic nit rogen plasma source in a molecular beam epitaxy growth chamber has been stu died. The resulting nitrogen induced GaAs(001) (3X3) reconstruction was inv estigated by in situ reflection high energy electron diffraction and x-ray photoemission spectroscopy (XPS). It was found that this reconstruction is only obtained in the temperature range 400-580 degrees C with a very low do se of atomic nitrogen. The nitrogen coverage corresponding to the (3X3) rec onstruction was determined by quantitative XPS to be 0.30+/-0.09 ML, Below 400 degrees C an As-N species of disordered structure was found on the GaAs (001) surface. Subsequent annealing at about 500 degrees C produced the (3X 3) reconstruction. Above 580 degrees C, nitridation lead to direct formatio n of beta-GaN islands. In addition, the (3X3) reconstruction was found to b e unstable to both exposure to atomic hydrogen and annealing. The N desorpt ion activation energy of the (3X3) was estimated to be 2.75+/-0.55 eV. A su rface phase diagram of the (3X3) has thus been deduced. (C) 1999 American V acuum Society. [S0734-211X(99)08804-6].