Species intermixing and phase transitions on the reconstructed (001) surfaces of GaAs and InAs

Scanning tunneling microscopy has been used to study the transition in surf ace structure between the As-terminated 2X4 and c(4X4) reconstructions on b oth GaAs(001) and InAs(001), as a function of surface temperature under an As-2 flux. For both materials, two-phase surface reconstructions exist thro ugh the transition regime; On GaAs, the two-phase surface consists of disor dered (2X4)-like structures plus a c(4x4)-like phase terminating one monola yer below the 2X4 surface. On InAs, a disordered asymmetric 1X3 phase occur s {a(1X3)} in addition to the main phases, one monolayer below each main ph ase. In both cases, simple addition of As via As-on-As chemisorption cannot account for the formation of the c(4X4) reconstruction from the 2X4 surfac e. The c(4x4) phase is inherently multilayered, which explains how the stru cture can form without the addition or removal of the group In component an d still maintain its layering registry with the residual 2X4 or a(lX3) phas e. One result of this formation process is the necessary intermixing of gro up III and group V species in the second layer of the c(4X4) reconstruction . Direct evidence of species intermixing on the top layer of the InAs(001)- a(1X3) structure is also shown and models for all of these reconstructions are proposed. [S0163-1829(99)00404-X].