SURFACE RECONSTRUCTIONS OF GAAS(111)A AND (111)B - A STATIC SURFACE PHASE STUDY BY REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION

GaAs(111)A and (111)B static surface phase maps have been generated under a variety of substrate temperature and incident As4 flux conditions ranging from, respectively, 400-700-degrees-C, and from 1 X 10(14) to 1 X 10(16) molecules cm-2 s-1. For the case of GaAs(111)A only a (2 X 2) reconstruction was observed. However, four GaAs(111)B surface reconstructions were identified below a critical As4 flux of J(As4)c congruent-to 5 X 10(15) molecules cm-2 s-1, viz.: (2 X 2); (1 X 1)LT; (square-root 19 X square-root 19); and, (1 X 1)HT. Above J(As4)c the (square-root 19 X square-root 19) surface phase was quenched, such that the (1 X 1)LT and (1 X 1)HT Structures merged to form a single (1 X 1) phase. The transitions to and from each of these surface phases were found to be reversible, occurring at very specific substrate temperatures for a given incident As4 flux. The activation energies (epsilon(A)) characterizing the reversible surface phase transitions were measured and compared with those on the GaAs(100) surface.